Tetrazene compound, tetrazene radical salt compound, tetrazene-type alcohol oxidation catalyst, tetrazene radical salt-type alcohol oxidation catalyst, and alcohol oxidation method using same

Abstract

Provided are: a new tetrazene compound, a new tetrazene radical salt compound, a new tetrazene-type alcohol oxidation catalyst, and a new tetrazene radical salt-type alcohol oxidation catalyst that are each suitably applicable as an alcohol oxidation catalyst capable of exhibiting a sufficiently high catalytic activity even in oxidation of a secondary alcohol, that are easy to produce, and that are each different from a polycyclic N-oxyl compound; and an alcohol oxidation method using the same. This tetrazene compound has an adamantane backbone represented by chemical formula (1) or a bicyclo backbone represented by chemical formula (2).

Description

Tetrazene compound, tetrazene radical salt compound, tetrazene-type alcohol oxidation catalyst, tetrazene radical salt-type alcohol oxidation catalyst, and alcohol oxidation method using the same

[0001] The present invention relates to a tetrazene compound, a tetrazene radical salt compound, a tetrazene-type alcohol oxidation catalyst, a tetrazene radical salt-type alcohol oxidation catalyst, and an alcohol oxidation method using the same. This application claims priority from Japanese Patent Application No. 2023-185949, filed on October 30, 2023, the contents of which are incorporated herein by reference.

[0002] The alcohol oxidation reaction, which oxidizes alcohols to carbonyl compounds, is one of the most fundamental reactions used in the organic synthesis of high-value-added compounds such as pharmaceuticals, pesticides, fragrances, and chemicals, and various methods have been developed to date. However, conventional methods have had problems in terms of safety and environmental impact, such as the need for high-temperature heating, the need to use toxic or explosive oxidizing agents, and the generation of large amounts of waste materials such as heavy metals.

[0003] Against this background, 2,2,6,6-tetramethylpiperidine 1-oxyl (hereinafter referred to as "TEMPO") has recently attracted attention as a catalyst capable of oxidizing alcohols even on a large scale, because it can oxidize alcohols using various co-oxidants under extremely mild conditions, such as temperatures between 0°C and room temperature, without using highly toxic and dangerous reagents.

[0004] Furthermore, the present inventors have recently discovered N-oxyl (nitroxyl radical) compounds having an azaadamantane skeleton (2-azaadamantane N-oxyl (hereinafter referred to as "AZADO") and 1-methyl-2-azaadamantane N-oxyl (hereinafter referred to as "1-Me-AZADO")), an N-oxyl compound having an azabicyclo[3.3.1]nonane skeleton (9-azabicyclo[3.3.1]nonane N-oxyl (hereinafter referred to as "ABNO")), an N-oxyl compound having an azanoradamantane skeleton (9-azanoradamantane N-oxyl (hereinafter referred to as "ABNO")), an N-oxyl compound having an aza ... It has been reported that polycyclic N-oxyl compounds such as N-oxyl (hereinafter referred to as "Nor-AZADO") can have higher alcohol oxidation catalytic activity than TEMPO (see, for example, Patent Documents 1 to 3 and Non-Patent Documents 1 to 4).

[0005] International Publication No. 2006 / 001387 Japanese Patent Application Laid-Open No. 2008-212853 International Publication No. 2012 / 008228

[0006] Masatoshi Shibuya et al., J. Am. Chem. Soc., 2006, Vol. 128, No. 26, pp. 8412-8413; Masatoshi Shibuya et al., J. Org. Chem., 2009, Vol. 74, No. 12, pp. 4619-4622; Masatoshi Shibuya et al., Synthesis, 2011, No. 21, pp. 3418-3425; Masaki Hayashi et al., Chem. Pharm. Bull., 2011, Vol. 59, No. 12, pp. 1570-1573

[0007] The present invention has been made in view of the problems associated with the prior art, and aims to provide novel tetrazene compounds, tetrazene radical salt compounds, tetrazene-type alcohol oxidation catalysts, and tetrazene radical salt-type alcohol oxidation catalysts that are suitably applicable as alcohol oxidation catalysts capable of exhibiting sufficiently high catalytic activity even in the oxidation of secondary alcohols, are easy to produce, and are different from the above-mentioned polycyclic N-oxyl compounds (AZADO, 1-Me-AZADO, ABNO, Nor-AZADO), as well as alcohol oxidation methods using the same.

[0008] As a result of extensive research aimed at achieving the above-mentioned object, the present inventors have discovered a novel tetrazene compound having an adamantane skeleton at both ends of the tetrazene, and have found that by using this compound as an alcohol oxidation catalyst, sufficiently high alcohol oxidation catalytic activity can be exhibited even for bulky secondary alcohols.

[0009]

[0009] Note that there have been no reports of tetrazene compounds having an adamantane skeleton as described above, and the present inventors were the first to discover the tetrazene compounds having an adamantane skeleton, tetrazene radical salt compounds, tetrazene-type alcohol oxidation catalysts, and tetrazene radical salt-type alcohol oxidation catalysts, as well as the ability to oxidize alcohols using these catalysts. Furthermore, the present inventors discovered that the tetrazene compounds having an adamantane skeleton and tetrazene radical salt compounds can be easily produced in several steps, leading to the completion of the present invention.

[0010] The present invention has the following aspects: [1] A tetrazene compound having an adamantane skeleton represented by the following chemical formula (1) or a bicyclo skeleton represented by the following chemical formula (2).

[0011] (In formula (1), n ​​is 0 or 1, and R １ is H, an alkyl group having 1 to 6 carbon atoms which may have a substituent, a phenyl group which may have a substituent, a carboxy group, an amide group, or an alkoxycarbonyl group having 1 to 6 carbon atoms; R ２ represents H, an alkyl group having 1 to 6 carbon atoms which may have a substituent, a carboxy group, an amide group, or an alkoxycarbonyl group having 1 to 6 carbon atoms; and X １ is H, OR ３ (R ３ represents H, an alkyl group having 1 to 6 carbon atoms, an acyl group, or a silyl group having 3 to 18 carbon atoms, which may have a substituent), NR ４ R ５ (R ４ , R ５ are each independently H, an optionally substituted alkyl group having 1 to 6 carbon atoms, an acyl group, an alkoxycarbonyl group, or a group in which the OH of a sulfo group has been substituted with a monovalent group, and R ４and R ５ may be bonded to form a ring), a halogen atom, an optionally substituted phenyl group, an optionally substituted alkyl group having 1 to 6 carbon atoms, ２ is H, OR ３ (R ３ represents H, an alkyl group having 1 to 6 carbon atoms, an acyl group, or a silyl group having 3 to 18 carbon atoms, which may have a substituent), NR ４ R ５ (R ４ , R ５ are each independently H, an optionally substituted alkyl group having 1 to 6 carbon atoms, an acyl group, an alkoxycarbonyl group, or a group in which the OH of a sulfo group has been substituted with a monovalent group, and R ４ and R ５ and may be bonded to form a ring), or a halogen atom. １ and X ２ Either of these is H.) (In formula (2), n is 0 or 1, R ６ 、 R ７ are each independently H or an alkyl group having 1 to 6 carbon atoms which may have a substituent, and X ３ , X ４ are each independently H, an alkyl group having 1 to 6 carbon atoms which may have a substituent, an aromatic group which may have a substituent, OR ３ (R ３ represents H, an alkyl group having 1 to 6 carbon atoms, an acyl group, or a silyl group having 3 to 18 carbon atoms, which may have a substituent), NR ４ R ５ (R ４ , R ５ are each independently H, an optionally substituted alkyl group having 1 to 6 carbon atoms, an acyl group, an alkoxycarbonyl group, or a group in which the OH of a sulfo group has been substituted with a monovalent group, and R ４ and R ５ may be bonded to form a ring), or a halogen atom, or X ３ and X ４ represents a keto group, an imino group (NR ８ ), oxime group (NOR ９ ), or a hydrazone group (NNR１０ R １１ ) may be formed, and the R ８ ~R １１ are each independently H, an alkyl group having 1 to 6 carbon atoms which may have a substituent, a phenyl group which may have a substituent, an acyl group, an alkoxycarbonyl group, or a group in which the OH of a sulfo group has been substituted with a monovalent group, and R １０ and R １１ may be bonded to form a ring. ３ and X ４ may be bonded to form a ring. ６ , R ７ , X ３ , X ４ Either of these is not H.)

[0012] [2] A tetrazene radical salt compound having an adamantane skeleton represented by the following chemical formula (3) or a bicyclo skeleton represented by the following chemical formula (4).

[0013] (In formula (3), n is 0 or 1, and R １ is H, an alkyl group having 1 to 6 carbon atoms which may have a substituent, a phenyl group which may have a substituent, a carboxy group, an amide group, or an alkoxycarbonyl group having 1 to 6 carbon atoms; R ２ represents H, an alkyl group having 1 to 6 carbon atoms which may have a substituent, a carboxy group, an amide group, or an alkoxycarbonyl group having 1 to 6 carbon atoms; and X １ is H, OR ３ (R ３ represents H, an alkyl group having 1 to 6 carbon atoms, an acyl group, or a silyl group having 3 to 18 carbon atoms, which may have a substituent), NR ４ R ５ (R ４ , R ５ are each independently H, an optionally substituted alkyl group having 1 to 6 carbon atoms, an acyl group, an alkoxycarbonyl group, or a group in which the OH of a sulfo group has been substituted with a monovalent group, and R ４ and R ５ may be bonded to form a ring), a halogen atom, an optionally substituted phenyl group, an optionally substituted alkyl group having 1 to 6 carbon atoms,２ is H, OR ３ (R ３ represents H, an alkyl group having 1 to 6 carbon atoms, an acyl group, or a silyl group having 3 to 18 carbon atoms, which may have a substituent), NR ４ R ５ (R ４ , R ５ are each independently H, an optionally substituted alkyl group having 1 to 6 carbon atoms, an acyl group, an alkoxycarbonyl group, or a group in which the OH of a sulfo group has been substituted with a monovalent group, and R ４ and R ５ and may be bonded to form a ring), or a halogen atom. １ and X ２ Either of these is H. Y － is a monovalent anion.) (In formula (4), n is 0 or 1, R ６ , R ７ are each independently H or an alkyl group having 1 to 6 carbon atoms which may have a substituent, and X ３ , X ４ are each independently H, an alkyl group having 1 to 6 carbon atoms which may have a substituent, an aromatic group which may have a substituent, OR ３ (R ３ represents H, an alkyl group having 1 to 6 carbon atoms, an acyl group, or a silyl group having 3 to 18 carbon atoms, which may have a substituent), NR ４ R ５ (R ４ , R ５ are each independently H, an optionally substituted alkyl group having 1 to 6 carbon atoms, an acyl group, an alkoxycarbonyl group, or a group in which the OH of a sulfo group has been substituted with a monovalent group, and R ４ and R ５ may be bonded to form a ring), or a halogen atom, or X ３ and X ４ represents a keto group, an imino group (NR ８ ), oxime group (NOR ９ ), or a hydrazone group (NNR １０ R １１ ) may be formed, and the R ８ ~R １１are each independently H, an alkyl group having 1 to 6 carbon atoms which may have a substituent, a phenyl group which may have a substituent, an acyl group, an alkoxycarbonyl group, or a group in which the OH of a sulfo group has been substituted with a monovalent group, and R １０ and R １１ may be bonded to form a ring. ３ and X ４ may be bonded to form a ring. － is a monovalent anion.)

[0014] [3] Y in the chemical formula (3) or (4) － is a conjugate base of a strong acid or a conjugate base of a weak acid.

[0015] [4] An alcohol oxidation catalyst for oxidizing alcohol, which is a tetrazene-type alcohol oxidation catalyst containing at least one selected from the group consisting of the tetrazene compound according to [1] and its derivatives.

[0016] [5] An alcohol oxidation catalyst for oxidizing alcohol, comprising at least one selected from the group consisting of the tetrazene radical salt compound and its derivatives according to [2] or [3].

[0017] [6] An alcohol oxidation catalyst for oxidizing alcohol, the tetrazene-type alcohol oxidation catalyst comprising a tetrazene compound having a bicyclo skeleton represented by the following chemical formula (5): (In the formula, n is 0 or 1.)

[0018] [7] A method for oxidizing an alcohol, comprising oxidizing an alcohol in the presence of the tetrazene-type alcohol oxidation catalyst according to [4] and a co-oxidant.

[0019] [8] The alcohol oxidation method according to [7], wherein the alcohol is a primary alcohol or a secondary alcohol.

[0020] [9] The method for oxidizing an alcohol according to [7] or [8], wherein the amount of the tetrazene-type alcohol oxidation catalyst added is 0.01 moles or more and 100 moles or less per 100 moles of all hydroxy groups in the alcohol.

[0021]

[10] A method for oxidizing an alcohol, comprising oxidizing an alcohol in the presence of the tetrazene radical salt type alcohol oxidation catalyst according to [5] and a co-oxidant.

[0022]

[11] The alcohol oxidation method according to

[10] , wherein the alcohol is a primary alcohol or a secondary alcohol.

[0023]

[12] The method for oxidizing an alcohol according to

[10] or

[11] , wherein the amount of the tetrazene radical salt-type alcohol oxidation catalyst added is 0.01 moles or more and 100 moles or less per 100 moles of all hydroxy groups in the alcohol.

[0024]

[13] A method for oxidizing an alcohol, comprising oxidizing an alcohol in the presence of the tetrazene-type alcohol oxidation catalyst according to [6] and a co-oxidant.

[0025]

[14] The alcohol oxidation method according to

[13] , wherein the alcohol is a primary alcohol or a secondary alcohol.

[0026]

[15] The method for oxidizing an alcohol according to

[13] or

[14] , wherein the amount of the tetrazene-type alcohol oxidation catalyst added is 0.01 moles or more and 100 moles or less per 100 moles of all hydroxy groups in the alcohol.

[0027] According to the present invention, it is possible to provide a novel tetrazene compound, a tetrazene radical salt compound, a tetrazene-type alcohol oxidation catalyst, a tetrazene radical salt-type alcohol oxidation catalyst, and an alcohol oxidation method using the same, which are suitably applicable as an alcohol oxidation catalyst capable of exhibiting sufficiently high catalytic activity even in the oxidation of secondary alcohols and are easy to produce.

[0028] 1 shows the results of cyclic voltammetry measurements of 1,2-di(2-azaadamantan-2-yl)diazene (DAD) and 2-azaadamantane N-oxyl (AZADO).

[0029] The present invention will be described in detail below based on preferred embodiments thereof.

[0030] [Tetrazene Compound Having Adamantane Skeleton or Bicyclo Skeleton] A tetrazene compound according to one embodiment of the present invention will be described. The tetrazene compound according to this embodiment is a tetrazene compound having an adamantane skeleton represented by the following chemical formula (1) or a bicyclo skeleton represented by the following chemical formula (2).

[0031] (In formula (1), n ​​is 0 or 1, and R １ is H, an alkyl group having 1 to 6 carbon atoms which may have a substituent, a phenyl group which may have a substituent, a carboxy group, an amide group, or an alkoxycarbonyl group having 1 to 6 carbon atoms; R ２ represents H, an alkyl group having 1 to 6 carbon atoms which may have a substituent, a carboxy group, an amide group, or an alkoxycarbonyl group having 1 to 6 carbon atoms; and X １ is H, OR ３ (R ３ represents H, an alkyl group having 1 to 6 carbon atoms, an acyl group, or a silyl group having 3 to 18 carbon atoms, which may have a substituent), NR ４ R ５ (R ４ , R ５ are each independently H, an optionally substituted alkyl group having 1 to 6 carbon atoms, an acyl group, an alkoxycarbonyl group, or a group in which the OH of a sulfo group has been substituted with a monovalent group, and R ４ and R ５ may be bonded to form a ring), a halogen atom, an optionally substituted phenyl group, an optionally substituted alkyl group having 1 to 6 carbon atoms, ２ is H, OR ３ (R ３represents H, an alkyl group having 1 to 6 carbon atoms, an acyl group, or a silyl group having 3 to 18 carbon atoms, which may have a substituent), NR ４ R ５ (R ４ , R ５ are each independently H, an optionally substituted alkyl group having 1 to 6 carbon atoms, an acyl group, an alkoxycarbonyl group, or a group in which the OH of a sulfo group has been substituted with a monovalent group, and R ４ and R ５ and may be bonded to form a ring), or a halogen atom. １ and X ２ Either of the following is H.) In the formula (1), when n is 0, strictly speaking it is a "noradamantane" skeleton, but such a skeleton is also included in the "adamantane skeleton" of the present invention.

[0032] (In formula (2), n is 0 or 1, R ６ 、 R ７ are each independently H or an alkyl group having 1 to 6 carbon atoms which may have a substituent, and X ３ , X ４ are each independently H, an alkyl group having 1 to 6 carbon atoms which may have a substituent, an aromatic group which may have a substituent, OR ３ (R ３ represents H, an alkyl group having 1 to 6 carbon atoms, an acyl group, or a silyl group having 3 to 18 carbon atoms, which may have a substituent), NR ４ R ５ (R ４ , R ５ are each independently H, an optionally substituted alkyl group having 1 to 6 carbon atoms, an acyl group, an alkoxycarbonyl group, or a group in which the OH of a sulfo group has been substituted with a monovalent group, and R ４ and R ５ may be bonded to form a ring), or a halogen atom, or X ３ and X ４ represents a keto group, an imino group (NR ８ ), oxime group (NOR ９ ), or a hydrazone group (NNR １０ R １１) may be formed, and the R ８ ~R １１ are each independently H, an alkyl group having 1 to 6 carbon atoms which may have a substituent, a phenyl group which may have a substituent, an acyl group, an alkoxycarbonyl group, or a group in which the OH of a sulfo group has been substituted with a monovalent group, and R １０ and R １１ may be bonded to form a ring. ３ and X ４ may be bonded to form a ring. ６ , R ７ , X ３ , X ４ Either of these is not H.)

[0033] In the tetrazene compound having an adamantane skeleton represented by the above chemical formula (1), R １ In the tetrazene compound having an adamantane skeleton represented by the above chemical formula (1), R is preferably H, a methyl group, an ethyl group, an isopropyl group, an n-butyl group, a tert-butyl group, a phenyl group, an amide group, or a methoxycarbonyl group. ２ In the tetrazene compound having an adamantane skeleton represented by the above chemical formula (1), X is preferably H, a methyl group, an ethyl group, an isopropyl group, an n-butyl group, a tert-butyl group, an amide group, or a methoxycarbonyl group. １ In the tetrazene compound having an adamantane skeleton represented by the above chemical formula (1), X is preferably H, a fluorine group, a chlorine group, a hydroxy group, a methoxy group, an acetamide group, a 4-benzyloxyphenyl group, or a 3-acetoxypropyl group. ２ As R, H, a fluorine group, a chlorine group, a methoxy group, and an acetamide group are preferred. １ , R ２ and X １ , X ２ The combination of １ , R ２ , X １ , X ２ If H, then R １ is a methyl group, R ２ , X １ , X ２ If H, then R１ , R ２ is a methyl group, X １ , X ２ If H, then R １ , R ２ , X ２ H, X １ When R is a fluorine group, １ , R ２ , X ２ H, X １ is a hydroxy group, R １ , R ２ , X ２ H, X １ When R is a methoxy group, １ , R ２ , X １ H, X ２ When R is a fluorine group, １ is a methyl group, R ２ , X ２ H, X １ In this specification, the term "silyl group having 3 to 18 carbon atoms" refers to a fluorine group. a ３ Si-(R a represents any hydrocarbon group), and the total number of carbon atoms in the hydrocarbon group is 3 to 18. Examples of the silyl group include trimethylsilyl, triethylsilyl, tert-butyldimethylsilyl, tert-butyldiphenylsilyl, triisopropylsilyl, and triphenylsilyl, and of these, tert-butyldiphenylsilyl is preferred.

[0034] In the tetrazene compound having a bicyclo skeleton represented by the above chemical formula (2), R ６ 、 R ７ are each independently preferably H, a methyl group, an ethyl group, an isopropyl group, an n-butyl group, or a tert-butyl group. ３ , X ４ are each independently preferably H, a methyl group, a 4-hydroxybutyl group, or an acetamide group. ３ and X ４ is a keto group, an imino group (NR８ ), oxime group (NOR ９ ), hydrazone group (NNR １０ R １１ ) is preferably formed. ８ As R, a phenyl group, a tert-butoxycarbonyl group, or a benzenesulfonyl group is preferred. ９ As R, a methyl group or a benzyl group is preferred. １０ , R １１ As for R １０ H, R １１ is preferably an acetyl group. ６ , R ７ and X ３ , X ４ The combination of ６ , R ７ is a methyl group, X ３ , X ４ If H, then R ６ , R ７ , X ４ H, X ３ When R is a methoxy group, ６ , R ７ , X ３ H, X ４ When is an acetamide group, R ６ , R ７ H, X ３ is a hydroxy group, X ４ When is a methyl group, R ６ , R ７ H, X ３ and X ４ is preferably a keto group.

[0035] The tetrazene compound of this embodiment, when used as an alcohol oxidation catalyst, can exhibit high catalytic activity in the oxidation of secondary alcohols and is easy to produce.Furthermore, the tetrazene compound of this embodiment, when used as an alcohol oxidation catalyst, can also exhibit high catalytic activity in the oxidation of primary alcohols.

[0036] [Method for Synthesizing a Tetrazene Compound Having an Adamantane Skeleton] The tetrazene compound represented by the above chemical formula (1) can be synthesized, for example, according to the reaction pathway shown in the following formula (6). That is, a secondary amine is nitrosated and reduced to obtain an N,N-dialkylhydrazine, which is then dimerized by air oxidative dimerization in the presence of a copper catalyst, thereby synthesizing the tetrazene.

[0037]

[0038] [Tetrazene radical salt compound having an adamantane skeleton or a bicyclo skeleton] A tetrazene radical salt compound according to one embodiment of the present invention will be described. The tetrazene radical salt compound of this embodiment is a tetrazene radical salt compound having an adamantane skeleton represented by the following chemical formula (3) or a bicyclo skeleton represented by the following chemical formula (4).

[0039] (In formula (3), n is 0 or 1, and R １ is H, an alkyl group having 1 to 6 carbon atoms which may have a substituent, a phenyl group which may have a substituent, a carboxy group, an amide group, or an alkoxycarbonyl group having 1 to 6 carbon atoms; R ２ represents H, an alkyl group having 1 to 6 carbon atoms which may have a substituent, a carboxy group, an amide group, or an alkoxycarbonyl group having 1 to 6 carbon atoms; and X １ is H, OR ３ (R ３ represents H, an alkyl group having 1 to 6 carbon atoms, an acyl group, or a silyl group having 3 to 18 carbon atoms, which may have a substituent), NR ４ R ５ (R ４ , R ５ are each independently H, an optionally substituted alkyl group having 1 to 6 carbon atoms, an acyl group, an alkoxycarbonyl group, or a group in which the OH of a sulfo group has been substituted with a monovalent group, and R ４ and R ５ may be bonded to form a ring), a halogen atom, an optionally substituted phenyl group, an optionally substituted alkyl group having 1 to 6 carbon atoms, ２ is H, OR ３(R ３ represents H, an alkyl group having 1 to 6 carbon atoms, an acyl group, or a silyl group having 3 to 18 carbon atoms, which may have a substituent), NR ４ R ５ (R ４ , R ５ are each independently H, an optionally substituted alkyl group having 1 to 6 carbon atoms, an acyl group, an alkoxycarbonyl group, or a group in which the OH of a sulfo group has been substituted with a monovalent group, and R ４ and R ５ and may be bonded to form a ring), or a halogen atom. １ and X ２ Either of these is H. Y － is a monovalent anion.)

[0040] (In formula (4), n is 0 or 1, R ６ , R ７ are each independently H or an alkyl group having 1 to 6 carbon atoms which may have a substituent, and X ３ , X ４ are each independently H, an alkyl group having 1 to 6 carbon atoms which may have a substituent, an aromatic group which may have a substituent, OR ３ (R ３ represents H, an alkyl group having 1 to 6 carbon atoms, an acyl group, or a silyl group having 3 to 18 carbon atoms, which may have a substituent), NR ４ R ５ (R ４ , R ５ are each independently H, an optionally substituted alkyl group having 1 to 6 carbon atoms, an acyl group, an alkoxycarbonyl group, or a group in which the OH of a sulfo group has been substituted with a monovalent group, and R ４ and R ５ may be bonded to form a ring), or a halogen atom, or X ３ and X ４ represents a keto group, an imino group (NR ８ ), oxime group (NOR ９ ), or a hydrazone group (NNR １０ R １１ ) may be formed, and the R ８ ~R １１are each independently H, an alkyl group having 1 to 6 carbon atoms which may have a substituent, a phenyl group which may have a substituent, an acyl group, an alkoxycarbonyl group, or a group in which the OH of a sulfo group has been substituted with a monovalent group, and R １０ and R １１ may be bonded to form a ring. ３ and X ４ may be bonded to form a ring. － is a monovalent anion.)

[0041] In the tetrazene radical salt compound having an adamantane skeleton represented by the above chemical formula (3), R １ In the tetrazene radical salt compound having an adamantane skeleton represented by the above chemical formula (3), R is preferably H, a methyl group, an ethyl group, an isopropyl group, an n-butyl group, a tert-butyl group, a phenyl group, an amide group, or a methoxycarbonyl group. ２ In the tetrazene radical salt compound having an adamantane skeleton represented by the above chemical formula (3), X is preferably H, a methyl group, an ethyl group, an isopropyl group, an n-butyl group, a tert-butyl group, an amide group, or a methoxycarbonyl group. １ In the tetrazene radical salt compound having an adamantane skeleton represented by the above chemical formula (3), X is preferably H, a fluorine group, a chlorine group, a hydroxy group, a methoxy group, an acetamide group, a 4-benzyloxyphenyl group, or a 3-acetoxypropyl group. ２ As R, H, a fluorine group, a chlorine group, a methoxy group, and an acetamide group are preferred. １ , R ２ and X １ , X ２ The combination of １ , R ２ , X １ , X ２ If H, then R １ is a methyl group, R ２ , X １ , X ２ If H, then R １ , R ２ is a methyl group, X １ , X ２ If H, then R１ , R ２ , X ２ H, X １ When R is a fluorine group, １ , R ２ , X ２ H, X １ is a hydroxy group, R １ , R ２ , X ２ H, X １ When R is a methoxy group, １ , R ２ , X １ H, X ２ When R is a fluorine group, １ is a methyl group, R ２ , X ２ H, X １ is preferably a fluorine group.

[0042] In the tetrazene radical salt compound having a bicyclo skeleton represented by the above chemical formula (4), R ６ , R ７ are each independently preferably H, a methyl group, an ethyl group, an isopropyl group, an n-butyl group, or a tert-butyl group. ３ , X ４ are each independently preferably H, a methyl group, a 4-hydroxybutyl group, or an acetamide group. ３ and X ４ is a keto group, an imino group (NR ８ ), oxime group (NOR ９ ), hydrazone group (NNR １０ R １１ ) is preferably formed. ８ As R, a phenyl group, a tert-butoxycarbonyl group, or a benzenesulfonyl group is preferred. ９ As R, a methyl group or a benzyl group is preferred. １０ , R １１ As for R １０ H, R １１ is preferably an acetyl group. ６ , R ７ and X ３ , X４ The combination of ６ , R ７ is a methyl group, X ３ , X ４ If H, then R ６ , R ７ , X ４ H, X ３ When R is a methoxy group, ６ , R ７ , X ３ H, X ４ When is an acetamide group, R ６ , R ７ H, X ３ is a hydroxy group, X ４ When is a methyl group, R ６ , R ７ H, X ３ and X ４ is preferably a keto group. Examples of the silyl group include trimethylsilyl, triethylsilyl, tert-butyldimethylsilyl, tert-butyldiphenylsilyl, triisopropylsilyl, and triphenylsilyl, and of these, tert-butyldiphenylsilyl is preferred.

[0043] Y in the above chemical formula (3) or (4) － is a monovalent anion, and examples thereof include the conjugate base of a strong acid or the conjugate base of a weak acid. An example of the conjugate base of a strong acid is the tetrakis(3,5-bis(trifluoromethyl)phenyl)borate ion ([B(C ６ H ３ (CF ３ ) ２ ) ４ ] － ), chloride ions (Cl － ), fluoride ion (F － ), tetrafluoroborate ion (BF ４ － ), perchlorate ion (ClO ４ － ), hexafluorophosphate ion (PF ６ － ), hexafluoroantimonate ion (SbF ６ － ), triflate ion (CF３ SO ３ － Alkyl sulfonate ions (RSO ３ － , R is an alkyl group having 1 to 4 carbon atoms). Examples of the conjugate base of a weak acid include acetate ion (CH ３ COO － ) and other carboxylic acid ions (RCOO － and R is an alkyl group having 1 to 17 carbon atoms. Among these, tetrakis(3,5-bis(trifluoromethyl)phenyl)borate ion is preferred from the viewpoints of solubility in organic solvents and ease of purification by silica gel column chromatography.

[0044]

[0045] The tetrazene radical salt compound of this embodiment, when used as an alcohol oxidation catalyst, can exhibit higher catalytic activity in the oxidation of secondary alcohols and is easy to produce. Furthermore, the tetrazene radical salt compound of this embodiment is expected to exhibit high catalytic activity in the oxidation of primary alcohols when used as an alcohol oxidation catalyst. Furthermore, the tetrazene radical salt compound of this embodiment can be reduced with a reducing agent such as calcium ascorbate to produce the tetrazene compound of the above-described embodiment. It is expected that utilizing this property will enable the evaluation of the reducing ability of novel reducing agents and the quantification of reducing agents.

[0046] [Method for Synthesizing Tetrazene Radical Salt Compound Having an Adamantane Skeleton] The tetrazene radical salt compound represented by the above chemical formula (3) can be synthesized, for example, according to the reaction pathway shown in the following formula (8). That is, tetrazene is one-electron oxidized with chlorine to form a chloride of the tetrazene radical, and then anion exchange with tetrakis(3,5-bis(trifluoromethyl)phenyl)borate ion (BArF) is performed, thereby isolating the BArF salt of the tetrazene radical cation.

[0047]

[0048] [Tetrazene-Type Alcohol Oxidation Catalyst] (First Embodiment) A tetrazene-type alcohol oxidation catalyst according to one embodiment of the present invention is an alcohol oxidation catalyst that oxidizes alcohol, and contains at least one compound selected from the group consisting of the tetrazene compounds and derivatives thereof according to the above-described embodiments.

[0049] The tetrazene-type alcohol oxidation catalyst of this embodiment contains at least one selected from the group consisting of the above-mentioned tetrazene compounds and their derivatives. The tetrazene-type alcohol oxidation catalyst of this embodiment may contain one of the above-mentioned tetrazene compounds and their derivatives alone, or may contain two or more of them in combination. Examples of the derivatives of the tetrazene compounds include hydrates and salts (such as hydrochlorides) of the tetrazene compounds having an adamantane skeleton represented by the above formula (1) or the tetrazene compounds having a bicyclo skeleton represented by the above formula (2).

[0050] The tetrazene-type alcohol oxidation catalyst of this embodiment may contain the above-mentioned tetrazene compound in an amount such that the content of the tetrazene compound is an effective amount as a catalyst. The catalyst may be made of at least one compound selected from the group consisting of the above-mentioned tetrazene compounds and their derivatives, and may further contain impurities derived from reagents used in the synthesis of the tetrazene compound, impurities generated during purification, and the like, within a range that does not impair the effects of the present invention.

[0051] Second Embodiment A tetrazene-type alcohol oxidation catalyst according to one embodiment of the present invention is an alcohol oxidation catalyst that oxidizes alcohol, and contains a tetrazene compound having a bicyclo skeleton represented by the following chemical formula (5).

[0052] (In the formula, n is 0 or 1.)

[0053] [Tetrazene Radical Salt-Type Alcohol Oxidation Catalyst] (First Embodiment) A tetrazene radical salt-type alcohol oxidation catalyst according to one embodiment of the present invention is an alcohol oxidation catalyst that oxidizes alcohol, and contains at least one compound selected from the group consisting of the tetrazene radical salt compounds and derivatives thereof according to the above-described embodiments.

[0054] The tetrazene radical salt-type alcohol oxidation catalyst of this embodiment contains at least one selected from the group consisting of the above-mentioned tetrazene radical salt compounds and derivatives thereof. The tetrazene radical salt-type alcohol oxidation catalyst of this embodiment may contain one of the above-mentioned tetrazene radical salt compounds and derivatives thereof alone, or may contain a combination of two or more of them.

[0055] The tetrazene radical salt-type alcohol oxidation catalyst of the present embodiment may contain the above-mentioned tetrazene radical salt compound in such an amount that the content of the tetrazene radical salt compound is an effective amount as a catalyst. The catalyst may be made of at least one compound selected from the group consisting of the above-mentioned tetrazene radical salt compounds and derivatives thereof, and may further contain impurities derived from reagents used in the synthesis of the tetrazene radical salt compound, impurities generated during purification, and the like, within a range that does not impair the effects of the present invention.

[0056] [Alcohol Oxidation Method] (First Embodiment) An alcohol oxidation method according to one embodiment of the present invention is a method of oxidizing alcohol in the presence of a tetrazene-type alcohol oxidation catalyst containing at least one compound selected from the group consisting of the tetrazene compounds and derivatives thereof of the above-described embodiments, and a co-oxidant.

[0057] In the alcohol oxidation method of this embodiment, the alcohol used as the substrate may be a primary alcohol represented by the following chemical formula (9) or a secondary alcohol represented by the following chemical formula (10).

[0058]

[0059]

[0060] In the above chemical formulas (9) and (10), R １２ and R １３ are each independently a substituent that does not adversely affect the oxidation reaction, and examples thereof include an optionally substituted linear or branched alkyl group, an optionally substituted cyclic alkyl group, an optionally substituted aromatic group, and an optionally substituted heterocyclic group. Furthermore, the alcohol used in the alcohol oxidation method of this embodiment may be a polyhydric alcohol having a plurality of structural units represented by the above chemical formulas (9) and (10) in the same molecule, but is preferably a monoalcohol having one hydroxy group, from the viewpoint of allowing the alcohol oxidation reaction to proceed more satisfactorily.

[0061] Examples of the alkyl group in the "optionally substituted straight-chain or branched-chain alkyl group" include alkyl groups having 1 to 16 carbon atoms, and among these, alkyl groups having 1 to 8 carbon atoms are preferred. Examples of such alkyl groups include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a 2-methylbutyl group, a neopentyl group, a 1-ethylpropyl group, an n-hexyl group, an isohexyl group, a 4-methylpentyl group, a 3-methylpentyl group, a 2-methylpentyl group, a 1-methylpentyl group, a 3,3-dimethylbutyl group, a 2,2-dimethylbutyl group, a 1,1 1,2-dimethylbutyl group, 1,3-dimethylbutyl group, 2,3-dimethylbutyl group, 2-ethylbutyl group, heptyl group, 1-methylhexyl group, 2-methylhexyl group, 3-methylhexyl group, 4-methylhexyl group, 2-methylheptyl group, 3-methylheptyl group, 4-methylheptyl group, 5-methylheptyl group, 6-methylheptyl group, 1-propylpentyl group, 2-ethylhexyl group, and 5,5-dimethylhexyl group.

[0062] The substituent on the alkyl group is not particularly limited as long as it does not affect the oxidation reaction, and examples thereof include alkyl groups having 1 to 6 carbon atoms, such as a methyl group, an ethyl group, or a propyl group; alkoxy groups having 1 to 6 carbon atoms, such as a methoxy group, an ethoxy group, or a propoxy group; halogen atoms such as fluorine, chlorine, bromine, or iodine; alkenyl groups having 2 to 6 carbon atoms, such as a vinyl group or an allyl group; alkynyl groups having 2 to 6 carbon atoms, such as an ethynyl group or a propargyl group; a hydroxy group; an amino group which may be substituted; a sulfonyl group which may be substituted; a cyano group; a nitroso group; an amidino group which may be substituted; a carboxy group; an alkoxycarbonyl group having 2 to 7 carbon atoms; an optionally substituted carbamoyl group; an aromatic group; an aromatic heterocyclic group; and acyl groups (an optionally substituted alkylcarbonyl group, or an optionally substituted arylcarbonyl group).

[0063] Examples of the cyclic alkyl group in the above-mentioned "optionally substituted cyclic alkyl group" include cycloalkyl groups having 3 to 7 carbon atoms, such as cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, and cycloheptyl group. In addition, examples of the substituent of the cyclic alkyl group include the same as the substituent in the above-mentioned "optionally substituted alkyl group".

[0064] Examples of the aromatic group in the above-mentioned "optionally substituted aromatic group" include monocyclic or fused polycyclic aromatic carbocyclic groups, and specific examples include aryl groups having 3 to 14 carbon atoms, such as a phenyl group, a naphthyl group, an anthryl group, an azulenyl group, a phenanthryl group, and an acenaphthylenyl group.

[0065] The heterocycle in the "optionally substituted heterocyclic group" may be a 5-membered monocyclic ring, a 6-membered monocyclic ring, or an aromatic heterocycle in a 6-5 or 6-6 fused ring system having 1 to 3 heteroatoms selected from the group consisting of oxygen, sulfur, and nitrogen atoms. Specific examples of such heterocyclic groups include furyl, thienyl, pyrrolyl, oxazolyl, isoxazolyl, thiazolyl, isothiazolyl, imidazolyl, pyrazolyl, 1,2,3-oxadiazolyl, 1,2,4-oxadiazolyl, 1,3,4-oxadiazolyl, furazanyl, 1,2,3-thiadiazolyl, 1,2,4-thiadiazolyl, and 1,3,4-thiadiazolyl. monocyclic aromatic heterocyclic groups such as a 1,2,3-triazolyl group, a 1,2,4-triazolyl group, a tetrazolyl group, a pyridyl group, a pyridazinyl group, a pyrimidinyl group, a pyrazinyl group, and a triazinyl group; a benzofuranyl group, an isobenzoxalyl group, a 1,2-benzisoxazolyl group, a benzothiazolyl group, a benzopyranyl group, a 1,2-benzisothiazolyl group, a 1H-benzotriazolyl group, a quinolyl group, an isoquinoline group, a phenyl group, a cinnolinyl group, a quinazolyl group, a quinoxalinyl group, a phthalazinyl group, a naphthyridinyl group, a purinyl group, a buteridinyl group, a carbazolinyl group, an α-carbolinyl group, a β-carbolinyl group, a γ-carbolinyl group, an acridinyl group, a phenoxazinyl group, a phenothiazinyl group, a phenazinyl group, a phenoxathiinyl group, a thianthrenyl group, a phenatridinyl group, a phenanthrolinyl group, an indolizinyl group, a pi and 8- to 12-membered fused polycyclic aromatic heterocyclic groups such as a pyrazolo[1,2-b]pyridazinyl group, a pyrazolo[1,5-a]pyridyl group, an imidaso[1,2-a]pyridyl group, an imidazo[1,5-a]pyridyl group, an imidazo[1,2-b]pyridazinyl group, an imidazo[1,2-a]pyrimidinyl group, a 1,2,4-triazolo[4,3-a]pyridyl group, and a 1,2,4-triazolo[4,3-b]pyridazinyl group. In addition, examples of the substituents of the aromatic group and the heterocyclic group include the same as those of the substituents in the above-mentioned "optionally substituted alkyl group."

[0066] The alcohol oxidation method of the present embodiment may involve adding the tetrazene-type alcohol oxidation catalyst of the above-described embodiment to the alcohol that is the reaction substrate, or may involve adding the alcohol to the tetrazene-type alcohol oxidation catalyst of the above-described embodiment.

[0067] The amount of the tetrazene-type alcohol oxidation catalyst added is preferably 0.01 mol or more and 100 mol or less, and more preferably 0.1 mol or more and 10 mol or less, relative to 100 mol of all hydroxy groups in the alcohol. If the amount of the tetrazene-type alcohol oxidation catalyst added is less than the lower limit, the reaction tends to not proceed, the reaction rate tends to decrease, or the reaction tends to stop midway. On the other hand, if the amount of the tetrazene-type alcohol oxidation catalyst added exceeds the upper limit, it tends to become difficult to control the reaction rate. Furthermore, in this embodiment, even if the amount of the tetrazene-type alcohol oxidation catalyst added is small (e.g., 0.1 mol or more and 1 mol or less relative to 100 mol of all hydroxy groups in the alcohol), sufficiently high alcohol oxidation catalytic activity is exhibited.

[0068] In the alcohol oxidation method of this embodiment, the alcohol is oxidized in the presence of the tetrazene-type alcohol oxidation catalyst and a co-oxidant. In the alcohol oxidation method of this embodiment, the co-oxidant oxidizes the tetrazene-type alcohol oxidation catalyst (catalytic oxidation), and then the oxidized tetrazene-type alcohol oxidation catalyst oxidizes the substrate alcohol (substrate oxidation), thereby progressing the reaction. In this reaction, the tetrazene-type alcohol oxidation catalyst is reduced in association with the oxidation reaction of the substrate. The reduced tetrazene-type alcohol oxidation catalyst is again oxidized by the co-oxidant, and the oxidized tetrazene-type alcohol oxidation catalyst oxidizes the substrate, thus completing an oxidation cycle.

[0069] Such a co-oxidizing agent can be appropriately selected from those commonly used in oxidation reactions using TEMPO, for example, and is not particularly limited, and examples thereof include peroxy acids, hydrogen peroxide, hypohalous acids and salts thereof, perhalogen acids and salts thereof, persulfates, halides, halogenating agents such as N-bromosuccinimide, trihalogenated isocyanuric acids, diacetoxyiodoarenes, oxygen, and mixtures thereof. Among these, preferred examples of the co-oxidizing agent include peracetic acid, m-chloroperbenzoic acid, hydrogen peroxide, sodium hypochlorite, lithium hypochlorite, potassium hypochlorite, calcium hypochlorite, sodium hypobromite, lithium hypobromite, potassium hypobromite, calcium hypobromite, sodium hydrogen persulfate, sodium periodate, periodic acid, trichloroisocyanuric acid, tribromoisocyanuric acid, N-bromosuccinimide, N-chlorosuccinimide, chlorine, bromine, and iodine.

[0070] The amount of the co-oxidizing agent to be added depends on the type of the co-oxidizing agent, and therefore cannot be generally stated, but it is usually preferably 33 moles or more, more preferably 40 moles or more and 150 moles or less, relative to 100 moles of the total hydroxyl groups in the alcohol.For example, when sodium hypochlorite is used as the co-oxidizing agent, it is preferable that the amount of sodium hypochlorite is 100 moles or more relative to 100 moles of the total hydroxyl groups in the alcohol.If the amount of the co-oxidizing agent to be added is less than the lower limit, the reaction tends to not proceed, the reaction rate tends to decrease, or the reaction tends to stop midway.

[0071] Furthermore, for example, when using the sodium hypochlorite as the co-oxidant, in order to further promote reaction, it is preferable to further use other co-oxidants such as alkali metal halide or additives such as quaternary ammonium salt in combination.Thus, the preferred additives to be used in combination with sodium hypochlorite are tetrabutylammonium chloride, tetrabutylammonium bromide, sodium bromide, potassium bromide, and their mixtures.In addition, the amount of these additives is preferably 10 mol or less relative to 100 mol of the sodium hypochlorite.

[0072] Furthermore, in the alcohol oxidation method of this embodiment, known solvents may be used appropriately as long as the effects of the present invention are not impaired. Examples of such solvents include aliphatic hydrocarbons such as hexane, heptane, and petroleum ether; aromatic hydrocarbons such as benzene, toluene, and xylene; nitriles such as acetonitrile and propionitrile; halogenated hydrocarbons such as dichloromethane, chloroform, 1,2-dichloroethane, and carbon tetrachloride; ethers such as diethyl ether, diisopropyl ether, tetrahydrofuran, dioxane, dimethoxyethane, and diethylene glycol dimethyl ether; amides such as formamide, dimethylformamide, dimethylacetamide, and hexamethylphosphoric acid triamide; sulfoxides such as dimethyl sulfoxide; esters such as ethyl formate, ethyl acetate, propyl acetate, butyl acetate, and diethyl carbonate; sulfolane; and water. These may be used alone or in combination.

[0073] Furthermore, as the solvent, from the viewpoint of tending to further improve the reaction efficiency, aliphatic hydrocarbons, aromatic hydrocarbons, nitriles, halogenated hydrocarbons, esters, water, and mixtures thereof are preferred, dichloromethane, acetonitrile, toluene, ethyl acetate, isopropyl acetate, water, and mixtures thereof are more preferred, and dichloromethane, acetonitrile, a dichloromethane-water mixed solution, an acetonitrile-water mixed solution, a toluene-water mixed solution, and an ethyl acetate-water mixed solution are even more preferred.

[0074] When a solvent is used, the concentration of the solvent is preferably 1 mL or more and 5 mL or less per 1 mmol of alcohol.

[0075] In addition, in the alcohol oxidation method of this embodiment, a buffer may be further added within a range that does not impair the effects of the present invention. Examples of such buffers include alkali metal or alkaline earth metal carbonates, alkali metal or alkaline earth metal bicarbonates, alkali metal or alkaline earth metal hydroxides, alkali metal or alkaline earth metal phosphates, and alkali metal or alkaline earth metal acetates. These may be used alone or in combination of two or more. Furthermore, preferred buffers are sodium bicarbonate, sodium carbonate, sodium acetate, sodium dihydrogen phosphate, and disodium hydrogen phosphate. When these buffers are added, the amount added is preferably 5,000 mol or less per mol of the tetrazene compound contained in the alcohol oxidation catalyst.

[0076] The reaction temperature in the alcohol oxidation method of this embodiment cannot be generally determined because it depends on the types of the alcohol and the co-oxidant, but is usually −80° C. to 120° C., and preferably 0° C. to 40° C. The reaction time also cannot be generally determined because it depends on the reaction temperature, and in this embodiment, the reaction proceeds particularly quickly, but is usually preferably 0.3 hours to 12 hours.

[0077] By using the alcohol oxidation method of this embodiment, the alcohol can be oxidized to produce the corresponding aldehyde or ketone in high yield. Furthermore, the reaction product obtained by oxidation can be isolated after the reaction is completed by an isolation procedure such as extraction, recrystallization, or column chromatography. Two or more of the isolation procedures may be combined.

[0078] [Alcohol Oxidation Method] (Second Embodiment) An alcohol oxidation method according to one embodiment of the present invention is a method of oxidizing alcohol in the presence of a tetrazene radical salt-type alcohol oxidation catalyst containing at least one compound selected from the group consisting of the tetrazene radical salt compounds and derivatives thereof of the above-described embodiments, and a co-oxidant.

[0079] In the alcohol oxidation method of this embodiment, as in the first embodiment, the substrate alcohol may be a primary alcohol represented by the above chemical formula (9) or a secondary alcohol represented by the above chemical formula (10).

[0080] The alcohol oxidation method of the present embodiment may involve adding the tetrazene radical salt-type alcohol oxidation catalyst of the above-described embodiment to the alcohol that is the reaction substrate, or may involve adding the alcohol to the tetrazene radical salt-type alcohol oxidation catalyst of the above-described embodiment.

[0081] The amount of the tetrazene radical salt-type alcohol oxidation catalyst added is preferably 0.01 mol or more and 100 mol or less, and more preferably 0.1 mol or more and 10 mol or less, relative to 100 mol of all hydroxy groups in the alcohol. If the amount of the tetrazene radical salt-type alcohol oxidation catalyst added is less than the lower limit, the reaction tends to not proceed, the reaction rate tends to decrease, or the reaction tends to stop midway. On the other hand, if the amount of the tetrazene radical salt-type alcohol oxidation catalyst added exceeds the upper limit, it tends to become difficult to control the reaction rate. Furthermore, in this embodiment, even if the amount of the tetrazene radical salt-type alcohol oxidation catalyst added is small (for example, 0.1 mol or more and 1 mol or less relative to 100 mol of all hydroxy groups in the alcohol), sufficiently high alcohol oxidation catalytic activity is exhibited.

[0082] In the alcohol oxidation method of this embodiment, similarly to the first embodiment, the alcohol is oxidized in the presence of the tetrazene radical salt-type alcohol oxidation catalyst and a co-oxidant.

[0083] Furthermore, in the alcohol oxidation method of this embodiment, a known solvent may be used as appropriate, as in the first embodiment, within a range that does not impair the effects of the present invention.

[0084] In the alcohol oxidation method of this embodiment, a buffer may be further added, as in the first embodiment, within a range that does not impair the effects of the present invention.

[0085] The reaction temperature in the alcohol oxidation method of this embodiment cannot be generally determined because it depends on the types of the alcohol and the co-oxidant, but is usually −80° C. to 120° C., and preferably 0° C. to 40° C. The reaction time also cannot be generally determined because it depends on the reaction temperature, and in this embodiment, the reaction proceeds particularly quickly, but is usually preferably 0.3 hours to 12 hours.

[0086] By using the alcohol oxidation method of this embodiment, the alcohol can be oxidized to produce the corresponding aldehyde or ketone in high yield. Furthermore, the reaction product obtained by oxidation can be isolated after the reaction is completed by an isolation procedure such as extraction, recrystallization, or column chromatography. Two or more of the isolation procedures may be combined.

[0087] [Alcohol Oxidation Method] (Third Embodiment) An alcohol oxidation method according to one embodiment of the present invention is a method of oxidizing an alcohol in the presence of a tetrazene-type alcohol oxidation catalyst containing the tetrazene compound having a bicyclo skeleton represented by chemical formula (5) of the above-described embodiment, and a co-oxidant.

[0088] In the alcohol oxidation method of this embodiment, as in the first embodiment, the substrate alcohol may be a primary alcohol represented by the above chemical formula (9) or a secondary alcohol represented by the above chemical formula (10).

[0089] The alcohol oxidation method of the present embodiment may involve adding the tetrazene-type alcohol oxidation catalyst of the above-described embodiment to the alcohol that is the reaction substrate, or may involve adding the alcohol to the tetrazene-type alcohol oxidation catalyst of the above-described embodiment.

[0090] The amount of the tetrazene-type alcohol oxidation catalyst added is preferably 0.01 mol or more and 100 mol or less, and more preferably 0.1 mol or more and 10 mol or less, relative to 100 mol of all hydroxy groups in the alcohol. If the amount of the tetrazene-type alcohol oxidation catalyst added is less than the lower limit, the reaction tends to not proceed, the reaction rate tends to decrease, or the reaction tends to stop midway. On the other hand, if the amount of the tetrazene-type alcohol oxidation catalyst added exceeds the upper limit, it tends to become difficult to control the reaction rate. Furthermore, in this embodiment, even if the amount of the tetrazene-type alcohol oxidation catalyst added is small (e.g., 0.1 mol or more and 1 mol or less relative to 100 mol of all hydroxy groups in the alcohol), sufficiently high alcohol oxidation catalytic activity is exhibited.

[0091] In the alcohol oxidation method of this embodiment, similarly to the first embodiment, the alcohol is oxidized in the presence of the tetrazene-type alcohol oxidation catalyst and a co-oxidant.

[0092] Furthermore, in the alcohol oxidation method of this embodiment, a known solvent may be used as appropriate, as in the first embodiment, within a range that does not impair the effects of the present invention.

[0093] In the alcohol oxidation method of this embodiment, a buffer may be further added, as in the first embodiment, within a range that does not impair the effects of the present invention.

[0094] The reaction temperature in the alcohol oxidation method of this embodiment cannot be generally determined because it depends on the types of the alcohol and the co-oxidant, but is usually −80° C. to 120° C., and preferably 0° C. to 40° C. The reaction time also cannot be generally determined because it depends on the reaction temperature, and in this embodiment, the reaction proceeds particularly quickly, but is usually preferably 0.3 hours to 12 hours.

[0095] By using the alcohol oxidation method of this embodiment, the alcohol can be oxidized to produce the corresponding aldehyde or ketone in high yield. Furthermore, the reaction product obtained by oxidation can be isolated after the reaction is completed by an isolation procedure such as extraction, recrystallization, or column chromatography. Two or more of the isolation procedures may be combined.

[0096] The present invention will be described in more detail below based on examples, but the present invention is not limited to the following examples.

[0097] The compounds obtained in each example were analyzed by nuclear magnetic resonance analysis (NMR: １ H-NMR, １３ The samples were analyzed by C-NMR, infrared absorption spectroscopy (IR), mass spectroscopy (MS), high-resolution mass spectroscopy (electron ionization) (HRMS (EI)), and elemental analysis (Anal.). １ The multiplicity in H-NMR is represented by s = singlet, d = doublet, t = triplet, ddd = double of doublet of doublets (double of doublet of doublet), tt = triplet of triplets (triplet of triplets), dtd = double of triplet of doublets (double of triplet of doublet), dddd = double of doublet of doublet of doublet (double of doublet of doublet of doublet), and m = multiplet. J represents a coupling constant. In each NMR, CDCl ３ was used as the solvent.

[0098] Example 1 Synthesis of 1,2-di(2-azaadamantan-2-yl)diazene

[0099]

[0100] According to the reaction pathway shown in formula (11) above, a 1,2-di(2-azaadamantan-2-yl)diazene (hereinafter referred to as DAD) compound represented by the following chemical formula (12) was synthesized. The starting material, 2-azaadamantane, was synthesized by the method reported by Shibuya et al. (Shibuya Masatoshi et al., Synthesis, 2011, No. 21, pp. 3418-3425 (Non-Patent Document 3)).

[0101]

[0102] <Synthesis of 2-nitroso-2-azaadamantane>

[0103]

[0104] 2-Nitroso-2-azaadamantane was synthesized according to the reaction pathway shown in formula (13) above. Specifically, first, acetic acid (0.33 mL, 5.5 mmol) and sodium nitrite (2.51 g, 36.4 mmol) were added to a solution of 2-azaadamantane (500 mg, 3.64 mmol) in water (7.3 mL) at room temperature. This solution was stirred at 70°C for 2 hours, then cooled to room temperature (25°C), and organic matter was extracted from the aqueous layer with diethyl ether. The organic layer was washed with saturated brine, dried over sodium sulfate, and concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography to obtain a yellow solid of 2-nitroso-2-azaadamantane (520 mg, 3.13 mmol, 86% yield) as a hexane-ethyl acetate (2:1 volume ratio) eluate.

[0105] Regarding the 2-nitroso-2-azaadamantane obtained below: １ H-NMR, １３ The results of C-NMR, IR, MS, and HRMS (EI) are shown below.

[0106] １ ​H-NMR (400MHz): δ5.38 (s, 1H), 4.93 (s, 1H), 2.19 (s, 2H), 2.02 (s, 4H), 1.97-1.96 (m, 2H), 1.82-1.71 (m, 4H). １３ C-NMR (100MHz): δ: 55.2, 44.3, 36.8, 35.3, 34.9, 27.2. IR(neat[cm －１ ]): 2927, 2855. MS [m / z]: 166 (M ＋ ), 136 (100%). HRMS (EI): Calcd. for C ９ H １４ N ２ O:166.1106, found:116.1108.

[0107] <Synthesis of DAD>

[0108]

[0109] DAD was synthesized according to the reaction pathway shown in the above formula (14). That is, first, 2-nitroso-2-azaadamantane (200 mg, 1.20 mmol) in diethyl ether (Et ２A solution of 2,2'-bis(2,2'-bipyridine) and 2,2'-bis(2,2'-dihydropyridine) was added portionwise at 0°C. After stirring this solution at room temperature for 2 hours, diethyl ether, water, and 10% sodium hydroxide solution were slowly added at 0°C, and the mixture was stirred at room temperature (25°C) for 1 hour. The mixture was then filtered through Celite and concentrated under reduced pressure to obtain 2-azaadamantan-2-amine (166 mg) as a white solid. This compound was used in the next reaction without purification. Next, copper iodide (20.8 mg, 0.109 mmol) and 2,2'-bipyridine (20.4 mg, 0.131 mmol) were dissolved in acetonitrile (5.0 mL). To this solution, a solution of 2-azaadamantan-2-amine (166 mg) synthesized previously in acetonitrile (6.0 mL) was slowly added dropwise at 0°C over 3 hours. After stirring for 12 hours at room temperature (25°C) in the open air, tetramethylethylenediamine (32 µL, 0.22 mmol) was added and stirred for several minutes. Water was added to the solution, and the aqueous layer was extracted with dichloromethane and removed. The organic layer was washed with saturated brine, dried over sodium sulfate, and concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography to obtain a white solid of DAD (101 mg, 0.336 mmol, 56% yield (2 steps)) as a hexane-ethyl acetate (4:1 volume ratio) eluate.

[0110] The following DADs are obtained: １ H-NMR, １３ The results of C-NMR, IR, MS, and HRMS (EI) are shown below.

[0111] １ H-NMR (400MHz): δ4.07 (s, 4H), 2.02 (s, 4H), 2.00 (d, J = 10.6Hz, 8H), 1.84 (s, 4H), 1.66 (d, J = 10.6Hz, 8H). １３ C-NMR (100MHz): δ: 51.1, 36.5, 34.0, 27.4. IR(neat[cm －１ ]): 2922, 2846. MS [m / z]: 300 (M ＋ ), 80 (100%). HRMS (EI): Calcd. for C １８ H ２８ N ４ ​:300.2314, found:300.2308.

[0112] Example 2 Synthesis of DAD Radical Salt (BArF Salt)

[0113]

[0114] A DAD radical salt (BArF salt) represented by the following chemical formula (16) was synthesized according to the reaction pathway shown in the above formula (15). The starting material, DAD represented by the above chemical formula (12), was synthesized according to the reaction pathway shown in the above formula (11).

[0115]

[0116] <Synthesis of DAD Radical Salt (BArF Salt)> The DAD radical salt (BArF Salt) represented by the above chemical formula (16) was synthesized according to the reaction pathway shown in the above formula (15). That is, first, chlorine gas was bubbled into a carbon tetrachloride (3.3 mL) solution of DAD (100 mg, 0.332 mmol) at room temperature (25° C.) (chlorine gas was generated freshly by adding concentrated hydrochloric acid dropwise to manganese dioxide under heated conditions). The precipitated red solid was then filtered, washed with diethyl ether, and dried to obtain a red solid of DAD radical salt (chloride) (89 mg). This compound was used in the next reaction without purification. Next, sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate hydrate (247 mg, 0.279 mmol) was added to a solution of DAD radical salt (chloride) (89 mg) in tetrahydrofuran (2.7 mL) at room temperature. This solution was stirred at room temperature (25°C) for 2 hours, and then water was added. Organic matter was extracted from the aqueous layer with dichloromethane. The organic layer was dried over sodium sulfate and concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography to obtain a red solid of DAD radical cation (BArF salt) (175 mg, 0.150 mmol, 45% (2 steps)) as an eluate of chloroform-methanol (20:1 volume ratio).

[0117] The results of IR and elemental analysis of the obtained DAD radical salt (BArF salt) compound are shown below.

[0118] IR(neat[cm －１ ]): 3078, 3021, 2943, 2866, 1794, 1608, 1449. Anal. Calcd. for C ５０ H ４０ BF ２４ N ４ ・ :for C, 51.61; H, 3.46; N, 4.81; Found: C, 51.63; H, 3.61; N, 4.81.

[0119] <Single Crystal X-Ray Structural Analysis of DAD Radical Salt (BArF Salt)> Single crystals were prepared by vapor diffusion using the DAD radical salt (BArF Salt) synthesized in Example 2, with chloroform as a good solvent and n-hexane as a poor solvent. The resulting single crystals were selected and subjected to X-ray diffraction experiments. As a result, it was determined that the crystals belonged to a monoclinic system, with space group Cc, lattice constants a = 15.0246(13) Å, b = 13.8861(10) Å, c = 23.3019(19) Å, β = 96.968(3)°, and Z = 4. 33,792 reflection data were measured. Structural analysis was performed as follows. Phases were determined using the direct method (SHELXL), and non-hydrogen atom positions were determined by Fourier synthesis. The positions of hydrogen atoms bonded to carbon were calculated from the carbon atom positions.

[0120] Example 3: Synthesis of 1,2-bis(1-methyl-2-azaadamantan-2-yl)diazene

[0121]

[0122] According to the reaction pathway shown in the above formula (17), 1,2-bis(1-methyl-2-azaadamantan-2-yl)diazene (hereinafter referred to as "1-methyl-DAD") represented by the following chemical formula (18) was synthesized. The starting material, benzyl-1-methyl-2-azaadamantane-2-carboxylate, was synthesized by the method reported by Shibuya et al. (Shibuya Masatoshi et al., Synthesis, 2011, No. 21, pp. 3418-3425 (Non-Patent Document 3)).

[0123]

[0124] <Synthesis of 1-methyl-2-nitroso-2-azaadamantane>

[0125]

[0126] 1-Methyl-2-nitroso-2-azaadamantane was synthesized according to the reaction pathway shown in formula (19) above. Specifically, first, palladium-activated carbon (Pd 10%) (12.2 mg) was added to a methanol (4.3 mL) solution of benzyl-1-methyl-2-azaadamantane-2-carboxylate (122 mg, 426 μmol) in a reaction vessel purged with argon gas at room temperature. The vessel was then filled with hydrogen gas (1 atm), and the mixture was stirred at room temperature for 2.5 hours. The reaction vessel was then purged with argon gas, and the reaction solution was filtered through Celite. The resulting filtrate was concentrated under reduced pressure. Dichloromethane and saturated aqueous sodium carbonate solution were added to the resulting residue, and organic matter was extracted from the aqueous layer with dichloromethane. The organic layer was dried over potassium carbonate and concentrated under reduced pressure to obtain 1-methyl-2-azaadamantane (80 mg) as a pale yellow oil. This compound was used in the next reaction without purification. Next, to a solution of the obtained pale yellow oil (80 mg) in water (1.1 mL) were added acetic acid (45.7 μL, 796 μmol) and sodium nitrite (366 mg, 5.31 mmol) at room temperature. This solution was stirred at 70°C for 2 hours, then cooled to room temperature, and organic matter was extracted from the aqueous layer with diethyl ether. The organic layer was washed with saturated brine, dried over sodium sulfate, and concentrated under reduced pressure. The obtained residue was purified by silica gel column chromatography to obtain a yellow solid of 1-methyl-2-nitroso-2-azaadamantane (48.7 mg, 63% (two steps)) as a hexane-ethyl acetate (5:1 volume ratio to 2:1 volume ratio) eluate.

[0127] Regarding the 1-methyl-2-nitroso-2-azaadamantane obtained below: １ H-NMR, １３ The results of C-NMR, IR, MS, and HRMS (EI) are shown below.

[0128] １ ​H-NMR (400MHz): δ 5.51 (s, 1H), 2.17 (s, 2H), 1.94-1.81 (m, 6H), 1.76 (d, J = 12.8Hz, 2H), 1.68-1.58 (m, 5H). １３ C-NMR (100MHz): δ 60.0, 44.2, 43.9, 34.8, 34.5, 27.2, 26.5. IR(neat[cm －１ ]): 2929, 1410, 1333, 1242, 1122. MS [m / z]: 180 (M ＋ ), 56 (100%). HRMS (EI): Calcd. for C １０ H １６ N ２ O:180.1263, found:180.1266.

[0129] <Synthesis of 1-methyl-DAD>

[0130]

[0131] 1-Methyl-DAD was synthesized according to the reaction pathway shown in the above formula (20). That is, first, a solution of LAH (38 mg, 1.0 mmol) in diethyl ether (3.3 mL) was added to a solution of 1-methyl-2-nitroso-2-azaadamantane (120 mg, 666 μmol) in diethyl ether (Et ２A solution of 1-methyl-2-azaadamantan-2-amine (108 mg) was added portionwise at 0°C. After stirring at room temperature for 29.5 hours, diethyl ether, water, and 10% sodium hydroxide solution were slowly added at 0°C, and the mixture was stirred at room temperature for 15 minutes. The mixture was then filtered through Celite and concentrated under reduced pressure to obtain a white solid (108 mg) containing 1-methyl-2-azaadamantan-2-amine. This compound was used in the next reaction without purification. Next, copper iodide (12.4 mg, 65.0 μmol) and 2,2'-bipyridine (10.1 mg, 65.0 μmol) were dissolved in acetonitrile (1.9 mL). Acetonitrile (2.2 mL) was added to the white solid (108 mg) containing 1-methyl-2-azaadamantan-2-amine that had been synthesized separately. The solution was slowly added dropwise to a solution of copper iodide and 2,2'-bipyridine in acetonitrile at room temperature over 3 hours, and the undissolved solid was recovered. (This solid was confirmed to contain 1-methyl-DAD, and was mixed with the organic layer obtained after the subsequent extraction procedure and purified by silica gel column chromatography.) After stirring for 17 hours at room temperature in the open air, tetramethylethylenediamine (19.6 μL, 130 μmol) was added and stirred for 10 minutes. Water was added to the solution, and the organic matter was extracted from the aqueous layer with dichloromethane. The organic layer was further washed with saturated saline, dried over sodium sulfate, and concentrated under reduced pressure. The mixture of the resulting residue and the undissolved solid was purified by silica gel column chromatography to obtain a white solid of 1-methyl-DAD (36.9 mg, 112 μmol, 34% yield (two steps)) as a hexane-ethyl acetate (8:1 volume ratio to 4:1 volume ratio) eluate.

[0132] Regarding 1-methyl-DAD obtained below: １ H-NMR, １３ The results of C-NMR, IR, MS, and HRMS (EI) are shown below.

[0133] １ H-NMR (400MHz): δ 4.37 (s, 2H), 2.02 (s, 4H), 1.94 (d, J = 12.2Hz, 4H), 1.84-1.67 (m, 8H), 1.56 (s, 8H), 1.24 (s, 6H). １３ ​C-NMR (100MHz): δ 55.8, 48.7, 42.5, 35.9, 32.5, 27.9, 27.8. IR(neat[cm －１ ]): 2958, 2912, 2846, 1442. MS [m / z]: 328 (M ＋ ), 94 (100%). HRMS (EI): Calcd. for C ２０ H ３２ N ４ :328.2627, found:328.2639.

[0134] Example 4: Synthesis of 1-methyl-DAD radical salt (BArF salt)

[0135]

[0136] 1-methyl-DAD radical salt (BArF salt) represented by the following chemical formula (22) was synthesized according to the reaction pathway shown in the above formula (21). Note that the starting material, 1-methyl-DAD represented by the above chemical formula (18), was synthesized according to the reaction pathway shown in the above formula (17).

[0137]

[0138] <Synthesis of 1-methyl-DAD radical salt (BArF salt)> 1-methyl-DAD radical salt (BArF salt) represented by the above formula (22) was synthesized according to the reaction pathway shown in the above formula (21). Specifically, first, chlorine gas was bubbled into a carbon tetrachloride (4.8 mL) solution of 1-methyl-DAD (158 mg, 0.48 mmol) at room temperature (chlorine gas was generated freshly by adding concentrated hydrochloric acid dropwise to manganese dioxide under heated conditions). The precipitated red solid was then collected by filtration and washed with carbon tetrachloride. The resulting red solid was dried under reduced pressure to obtain a red solid (168 mg) of 1-methyl-DAD radical salt (chloride). This compound was used in the next reaction without purification. Next, sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate hydrate (430 mg, 0.49 mmol) was added to a solution of 1-methyl-DAD radical salt (chloride) (168 mg) in tetrahydrofuran (4.6 mL) at 0°C. This solution was stirred at room temperature for 2 hours, and then water was added. After extracting organic matter from the aqueous layer with dichloromethane, the organic layer was dried over sodium sulfate and concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography to obtain a red solid of 1-methyl-DAD radical salt (BArF salt) (107 mg, 89.9 μmol, 19% (2 steps)) as a chloroform-methanol (20:1 volume ratio) eluate.

[0139] The results of elemental analysis of the obtained 1-methyl-DAD radical salt (BArF salt) are shown below.

[0140] Anal. Calcd. for C ５２ H ４４ BF ２４ N ４ ・ :for C, 52.41; H, 3.72; N, 4.70; found: C, 52.46; H, 3.86; N, 4.65.

[0141] Example 5: Synthesis of 1,2-bis(5-methoxy-2-azaadamantan-2-yl)diazene

[0142]

[0143] According to the reaction pathway shown in formula (23) above, 1,2-bis(5-methoxy-2-azaadamantan-2-yl)diazene (hereinafter referred to as "5-methoxy-DAD") represented by the following chemical formula (24) was synthesized. The starting material, 2,2,2-trifluoro-1-(5-methoxy-2-azaadamantenyl)ethanone, was synthesized by the method reported by Shibuya et al. (Shibuya Masatoshi et al., J. Org. Chem., 2014, Vol. 79, No. 21, pp. 10256-10268).

[0144]

[0145] <Synthesis of 5-methoxy-2-nitroso-azaadamantane>

[0146]

[0147] 5-Methoxy-2-nitroso-2-azaadamantane was synthesized according to the reaction pathway shown in formula (25) above. Specifically, first, 10% aqueous sodium hydroxide solution (4.8 mL) was added to a solution of 2,2,2-trifluoro-1-(5-methoxy-2-azaadamantanyl)-1-ethanone (601 mg, 2.28 mmol) in ethanol (7.1 mL), and the mixture was stirred at room temperature for 2.5 hours. The mixture was then concentrated under reduced pressure, and chloroform was added to the resulting residue. Organic matter was extracted from the aqueous layer with chloroform. The organic layer was dried over potassium carbonate and concentrated under reduced pressure to obtain 5-methoxy-2-azaadamantane (370 mg) as a colorless oil. This compound was used in the next reaction without purification. Next, to a solution of the obtained colorless oil (370 mg) in water (4.4 mL) were added acetic acid (191 μL, 3.32 mmol) and sodium nitrite (1.53 g, 22.1 mmol) at room temperature. This solution was stirred at 70°C for 1.5 hours, then cooled to room temperature, and organic matter was extracted from the aqueous layer with diethyl ether. The organic layer was washed with saturated brine, dried over sodium sulfate, and concentrated under reduced pressure. The obtained residue was purified by silica gel column chromatography to obtain a yellow solid of 5-methoxy-2-nitroso-2-azaadamantane (298 mg, 67% (two steps)) as a hexane-ethyl acetate (4:1 volume ratio to 2:1 volume ratio) eluate.

[0148] Regarding the 5-methoxy-2-nitroso-2-azaadamantane obtained below: １ H-NMR, １３ The results of C-NMR, IR, MS, and HRMS (EI) are shown below.

[0149] １ H-NMR (400MHz): δ 5.49 (s, 1H), 5.12 (s, 1H), 3.24 (s, 3H), 2.44 (s, 1H), 2.03-1.81 (m, 6H), 1.78-1.56 (m, 4H). １３ C-NMR (100MHz): δ 71.2, 56.1, 48.3, 45.0, 40.1, 39.2, 38.3, 35.8, 33.9, 29.2 IR (neat [cm －１ ]): 3581, 3498, 2939, 2860, 1431. MS [m / z]: 196 (M ＋ ), 94 (100%). HRMS (EI): Calcd. for C １０ H １６ N ２ O ２ :196.1212, found:196.1207.

[0150] <Synthesis of 5-methoxy-DAD>

[0151]

[0152] 5-Methoxy-DAD was synthesized according to the reaction pathway shown in the above formula (26). That is, first, 5-methoxy-2-nitroso-2-azaadamantane (200 mg, 1.02 mmol) in diethyl ether (Et ２ ​A solution of 5-methoxy-2-azaadamantan-2-amine (5.1 mL) was added portionwise at 0°C. This solution was stirred at room temperature for 24 hours, and then diethyl ether, water, and 10% sodium hydroxide solution were slowly added at 0°C, followed by stirring at room temperature for 15 minutes. The mixture was then filtered through Celite and concentrated under reduced pressure to obtain a white solid (185 mg) containing 5-methoxy-2-azaadamantan-2-amine. This compound was used in the next reaction without purification. Next, copper iodide (19.4 mg, 102 μmol) and 2,2'-bipyridine (19.1 mg, 122 μmol) were dissolved in acetonitrile (4.3 mL). To this solution, a solution of the previously synthesized white solid (185 mg) containing 5-methoxy-2-azaadamantan-2-amine in acetonitrile (5.1 mL) was slowly added dropwise at 0°C over 3 hours. After stirring for 17 hours at room temperature in the open air, tetramethylethylenediamine (30.0 μL, 204 μmol) was added and stirred for 10 minutes. Water was added to the solution, and organic matter was extracted from the aqueous layer with dichloromethane. The organic layer was further washed with saturated brine, dried over sodium sulfate, and concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography to obtain a white solid of 5-methoxy-DAD (18.9 mg, 52.3 μmol, 10% yield (two steps)) as a hexane-ethyl acetate (3:1 volume ratio) eluate.

[0153] Regarding the 5-methoxy-DAD obtained below, １ H-NMR, １３ The results of C-NMR, IR, MS, and HRMS (EI) are shown below.

[0154] １ H-NMR (400MHz): δ 4.30 (s, 4H), 3.22 (s, 6H), 2.29 (s, 2H), 1.90 (t, J = 10.7Hz, 8H), 1.82 (s, 4H), 1.69-1.50 (m, 8H). １３ C-NMR (100MHz): δ 71.7, 52.8, 47.8, 39.9, 37.2, 33.3, 29.3. IR(neat[cm －１ ]): 2937, 2852, 1109, 1088, 1065. MS [m / z]: 360 (M ＋ ​), 275 (100%). HRMS (EI): Calcd. for C ２０ H ３２ N ４ O ２ :360.2525, found:360.2521.

[0155] Example 6 Synthesis of 1,2-bis(4-fluoro-2-azaadamantan-2-yl)diazene

[0156]

[0157] 1,2-bis(4-fluoro-2-azaadamantan-2-yl)diazene (hereinafter referred to as "4-fluoro-DAD") represented by the following chemical formula (28) was synthesized according to the reaction pathway shown in the above formula (27). The starting material, benzyl-bicyclo[3.3.1]nonenylcarbamate, was synthesized by the method reported by Nagasawa et al. (Shota Nagasawa et al., Asian J. Org. Chem., 2023, Vol. 12, No. 4, e202300031).

[0158]

[0159] <Synthesis of benzyl-4-fluoro-2-azaadamantane-2-carboxylate>

[0160]

[0161] Benzyl-4-fluoro-2-azaadamantane-2-carboxylate was synthesized according to the reaction pathway shown in formula (29) above. Specifically, first, Selectfluor (783 mg, 2.21 mmol) was added to a solution of benzyl-bicyclo[3.3.1]nonenylcarbamate (400 mg, 1.47 mmol) in acetonitrile (7.4 mL) at 0°C. The solution was warmed to room temperature and stirred for 68.5 hours. The reaction solution was then diluted with water, and organic matter was extracted from the aqueous layer with dichloromethane. The organic layer was further washed with saturated saline, dried over magnesium sulfate, and concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography to obtain a pale yellow oily mixture (279 mg) composed primarily of benzyl-4-fluoro-2-azaadamantane-2-carboxylate as a hexane-ethyl acetate (8:1 volume ratio) eluate.

[0162] Regarding the benzyl-4-fluoro-2-azaadamantane-2-carboxylate obtained below, １ The results of H-NMR are shown below.

[0163] １ H-NMR (400MHz): δ 7.36-7.31 (m, 5H), 5.14 (s, 2H), 4.69-4.57 (m, 1H), 4.47-4.26 (m, 2H), 2.24-1.60 (m, 10H).

[0164] <Synthesis of 4-fluoro-2-nitroso-2-azaadamantane>

[0165]

[0166] ​4-Fluoro-2-nitroso-2-azaadamantane was synthesized according to the reaction pathway shown in formula (30) above. Specifically, first, the reaction vessel was purged with argon gas, and palladium-activated carbon (Pd 10%) (27.9 mg) was added at room temperature to a methanol (4.8 mL) solution of a pale yellow oily mixture (279 mg) composed primarily of benzyl-4-fluoro-2-azaadamantane-2-carboxylate. The vessel was filled with hydrogen gas (1 atm), and the mixture was stirred at room temperature for 6.5 hours. The reaction vessel was then purged with argon gas, and the reaction solution was filtered through Celite. The resulting filtrate was washed with a 10% aqueous sodium hydroxide solution, and the organic layer was dried over potassium carbonate and concentrated under reduced pressure to obtain a pale yellow oil (137 mg) composed primarily of 4-fluoro-2-azaadamantane. This compound was used in the next reaction without purification. Next, to a solution of the obtained pale yellow oil (137 mg) in water (1.8 mL) were added acetic acid (76.0 μL, 1.32 mmol) and sodium nitrite (608 mg, 8.81 mmol) at room temperature. This solution was stirred at 70° C. for 2 hours, then cooled to room temperature, and organic matter was extracted from the aqueous layer with diethyl ether. The organic layer was washed with saturated brine, dried over sodium sulfate, and concentrated under reduced pressure. The obtained residue was purified by silica gel column chromatography to give a yellow solid mixture (123 mg, 69% (two steps)) composed mainly of 4-fluoro-2-nitroso-2-azaadamantane as a hexane-ethyl acetate (4:1 volume ratio) eluate.

[0167] Regarding the 4-fluoro-2-nitroso-2-azaadamantane obtained below: １ The results of H-NMR are shown below.

[0168] １ H-NMR (400MHz): δ 5.46 (s, 0.5H), 5.27 (s, 0.5H), 5.05 (s, 0.5H), 4.93 (s, 0.5H), 4.74 (dt , J=50, 3.9Hz, 0.5H), 4.41 (dt, J=50, 3.9Hz, 0.5H), 2.46-1.50 (m, 10H).

[0169] <Synthesis of 4-fluoro-DAD>

[0170] ​

[0171] 4-Fluoro-DAD was synthesized according to the reaction pathway shown in the above formula (31). That is, first, a yellow solid mixture (123 mg, 666 μmol) mainly composed of 4-fluoro-2-nitroso-2-azaadamantane was dissolved in diethyl ether (Et ２ A solution of 4-fluoro-2-azaadamantan-2-amine (1.1 mL) was added portionwise at 0°C. After stirring this solution at room temperature for 2 hours, diethyl ether, water, and 10% sodium hydroxide solution were slowly added at 0°C, and the mixture was stirred at room temperature for 15 minutes. The mixture was then filtered through Celite and concentrated under reduced pressure to obtain a white solid (112 mg) containing 4-fluoro-2-azaadamantan-2-amine. This compound was used in the next reaction without purification. Next, copper iodide (12.5 mg, 65.8 μmol) and 2,2'-bipyridine (10.3 mg, 65.8 μmol) were dissolved in acetonitrile (3.0 mL). To this solution, a solution of the previously synthesized white solid (112 mg) containing 4-fluoro-2-azaadamantan-2-amine in acetonitrile (3.6 mL) was slowly added dropwise at room temperature over 2 hours and 40 minutes. After stirring for 12 hours at room temperature in the open air, tetramethylethylenediamine (9.9 μL, 65.8 μmol) was added and stirred for 10 minutes. Water was added to the solution, and organic matter was extracted from the aqueous layer with dichloromethane. The organic layer was further washed with saturated brine, dried over sodium sulfate, and concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography using hexane-ethyl acetate (volume ratio of 15:1 to 10:1) as a eluent, and then purified by preparative thin-layer chromatography using toluene as a eluent to obtain a white solid of 4-fluoro-DAD (10.5 mg, 31.2 μmol, yield 9% (two steps)).

[0172] Regarding 4-fluoro-DAD obtained below: １ H-NMR, １３ The results of C-NMR, IR, MS, and HRMS (EI) are shown below.

[0173] １ ​H-NMR (400MHz): δ 4.70 (d, J=50Hz, 2H), 4.12 (d, J=78Hz, 4H), 2.26 (s, 2H), 2.12 (d, J= 14Hz, 2H) 2.06-1.87 (m, 8H), 1.86-1.77 (m, 4H), 1.73-1.59 (m, 4H). １３ C-NMR (100MHz): δ 90.8 (d, J = 4.0 Hz), 53.3, 53.0, 33.9, 33.8, 32.4 (d, J = 2.0 Hz), 32.3 (d, J = 2.0 Hz), 32.1, 32.0, 30.1, 28.2, 26.0. IR(neat[cm －１ ]): 2929, 2856, 1007, 957. MS [m / z]: 336 (M ＋ ), 79 (100%). HRMS (EI): Calcd. for C １８ H ２６ F ２ N ４ :336.2126, found:336.2127.

[0174] (Example 7) <Synthesis of 1,2-di(9-azanoradamantan-9-yl)diazene>

[0175]

[0176] According to the reaction pathway shown in the above formula (32), 1,2-di(9-azanoradamantane-9-yl)diazene (hereinafter referred to as "Nor-DAD") represented by the following chemical formula (33) was synthesized. The starting material, 9-benzyl-9-azanoradamantane, was synthesized by the method reported by Hayashi et al. (Hayashi Masaki et al., Chem. Pharm. Bull., 2011, Vol. 59, No. 12, pp. 1570-1573 (Non-Patent Document 4)).

[0177]

[0178] <Synthesis of 9-nitroso-9-azanoradamantane>

[0179]

[0180] 9-Nitroso-9-azanoradamantane was synthesized according to the reaction pathway shown in formula (34) above. Specifically, first, a reaction vessel was purged with argon gas, and palladium hydroxide-activated carbon (Pd 20%, approximately 50% water content) (50 mg) was added to an ethanol (12 mL) solution of 9-benzyl-9-azanoradamantane (500 mg, 2.34 mmol) at room temperature. The reaction vessel was filled with hydrogen gas (1 atm), and the mixture was stirred at room temperature for 44 hours. The reaction vessel was then purged with argon gas, and the reaction solution was filtered through Celite. The resulting filtrate was concentrated under reduced pressure to yield 9-azanoradamantane (355 mg) as a white solid. This compound was used in the subsequent reaction without purification. Next, to a solution of the obtained white solid (355 mg) in water (6.0 mL) were added acetic acid (260 μL, 4.32 mmol) and sodium nitrite (1.99 g, 28.8 mmol) at room temperature. This solution was stirred at 70°C for 3 hours, then cooled to room temperature, and the organic layer was extracted from the aqueous layer with diethyl ether. The organic layer was washed with saturated brine, dried over sodium sulfate, and concentrated under reduced pressure. The obtained residue was purified by silica gel column chromatography to obtain a yellow solid of 9-nitroso-9-azanoradamantane (250 mg, 66% (two steps)) as a hexane-ethyl acetate (20:1 volume ratio) eluate.

[0181] Regarding the 7-nitroso-azanoradamantane obtained below: １ H-NMR, １３ The results of C-NMR, IR, MS, and HRMS (EI) are shown below.

[0182] １ H-NMR (400MHz): δ 5.60 (s, 1H), 5.17 (s, 1H), 2.87 (t, J = 4.8Hz, 2H), 1.94-1.85 (m, 2H), 1.81-1.70 (m, 5H), 1.52 (s, 1H). １３ C-NMR (100MHz): δ 63.9, 52.7, 42.6, 41.8, 36.3. IR(neat[cm －１ ​]): 2973, 2920, 2879, 1456, 1418, 1354, 1321, 1308, 1274, 1237, 1179, 1076, 1040, 987, 964, 917, 788, 764. MS [m / z]: 152 (M ＋ ), 95 (100%). HRMS (EI): Calcd. for C ８ H １２ N ２ O:152.0950, found:152.0949.

[0183] <Synthesis of Nor-DAD>

[0184]

[0185] Nor-DAD was synthesized according to the reaction pathway shown in the above formula (35). That is, first, a solution of LAH (82.3 mg, 2.17 mmol) in diethyl ether (3.0 mL) was dissolved in 9-nitroso-9-azanoradamantane (220 mg, 1.45 mmol) in diethyl ether (Et ２A solution of 9-nitroso-9-azanoradamantane, 9-azanoradamantane-9-amine, and Nor-DAD was added portionwise at 0°C. This solution was stirred at room temperature for 24 hours, and then diethyl ether, water, and 10% sodium hydroxide solution were slowly added at 0°C, followed by stirring at room temperature for 30 minutes. The mixture was then filtered through Celite and concentrated under reduced pressure to obtain a mixture of 9-nitroso-9-azanoradamantane, 9-azanoradamantane-9-amine, and Nor-DAD. This mixture was purified by silica gel column chromatography to recover 9-nitroso-9-azanoradamantane (105 mg). The recovered raw material was again subjected to reduction with LAH according to the procedure described above, yielding a total of 9-azanoradamantane-9-amine (63 mg) and Nor-DAD (17 mg) in two reactions. The resulting 9-azanoradamantane-9-amine was unstable in air and was therefore immediately used in the next reaction. Next, copper iodide (8.7 mg, 46 μmol) and 2,2'-bipyridine (8.5 mg, 55 μmol) were dissolved in acetonitrile (2 mL). To this solution, an acetonitrile solution (6.0 mL) of the previously synthesized 9-azanoradamantane-9-amine (63 mg) was slowly added dropwise over 3.5 hours at room temperature. After stirring for 18 hours at room temperature in the open air, tetramethylethylenediamine (12 μL, 91 μmol) was added and stirred for 10 minutes. Water was added to the solution, and organic matter was extracted from the aqueous layer with dichloromethane. The organic layer was further washed with saturated saline, dried over sodium sulfate, and concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography to obtain a white solid, Nor-DAD (33 mg), as a eluate of hexane-ethyl acetate (10:1 volume ratio). The total amount and yield, including Nor-DAD (17 mg) obtained in the previous step, were 50 mg, 0.18 mmol, and 25% yield (two steps).

[0186] The following Nor-DAD １ H-NMR, １３ The results of C-NMR, IR, MS, and HRMS (EI) are shown below.

[0187] １ ​H-NMR (400MHz): δ 4.34 (s, 4H), 2.60 (t, J = 4.8Hz, 4H), 1.73 (d, J = 10.4Hz, 8H), 1.64-1.55 (m, 8H). １３ C-NMR (100MHz): δ 60.6, 40.7, 36.5. IR(neat[cm －１ ]): 2965, 2909, 2867, 1450, 1353, 1319, 1211, 1058, 1040, 1031, 964, 943, 903, 783. MS [m / z]: 272 (M ＋ ), 67 (100%). HRMS (EI): Calcd. for C １６ H ２４ N ４ :272.2001, found:272.2003.

[0188] Example 8 Synthesis of Nor-DAD Radical Salt (BArF Salt)

[0189]

[0190] Nor-DAD radical salt (BArF salt) represented by the following chemical formula (37) was synthesized according to the reaction pathway shown in the above formula (36). The starting material, Nor-DAD represented by the above chemical formula (35), was synthesized according to the reaction pathway shown in the above formula (32).

[0191]

[0192] <Synthesis of Nor-DAD Radical Salt (BArF Salt)> According to the reaction pathway shown in formula (36), Nor-DAD radical salt (BArF Salt) represented by chemical formula (37) was synthesized. Specifically, chlorine gas was first bubbled into a carbon tetrachloride (3.0 mL) solution of Nor-DAD (40 mg, 0.15 mmol) at room temperature (chlorine gas was generated fresh by adding concentrated hydrochloric acid dropwise to manganese dioxide under heating). The precipitated red solid was then collected by filtration and washed with carbon tetrachloride. The resulting red solid was dried under reduced pressure for 2 hours to obtain a red solid (31 mg) of Nor-DAD radical salt (chloride). This compound was used in the next reaction without purification. Next, sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate hydrate (94 mg, 0.11 mmol) was added to a solution of Nor-DAD radical salt (chloride) (31 mg) in tetrahydrofuran (1.0 mL) at 0°C. This solution was stirred at room temperature for 2 hours, and then water was added. After extracting organic matter from the aqueous layer with dichloromethane, the organic layer was dried over sodium sulfate and concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography to obtain a red solid of Nor-DAD radical salt (BArF salt) (20 mg, 17 μmol, 17% (2 steps)) as a chloroform-methanol (20:1 volume ratio) eluate.

[0193] The results of elemental analysis of the obtained Nor-DAD radical salt (BArF salt) are shown below.

[0194] Anal. Calcd. for C ４８ H ４０ BF ２４ N ４ ・ :for C, 50.77; H, 3.20; N, 4.93; found: C, 50.79; H, 3.37; N, 4.87.

[0195] (Example 9) <Synthesis of 1,2-di(9-azabicyclo[3.3.1]nonan-9-yl)diazene>

[0196]

[0197] According to the reaction pathway shown in formula (38) above, 1,2-di(9-azabicyclo[3.3.1]nonan-9-yl)diazene (hereinafter referred to as "DAND") represented by the following chemical formula (39) was synthesized. The starting material, 9-benzyl-9-azabicyclo[3.3.1]nonene, was synthesized by the method reported by Song et al. (Zhiguo J. Song et al., Organic Syntheses, 2020, Vol. 99, pp. 251-273).

[0198]

[0199] <Synthesis of 9-nitroso-9-azabicyclo[3.3.1]nonane>

[0200]

[0201] 9-Nitroso-9-azabicyclo[3.3.1]nonane was synthesized according to the reaction pathway shown in formula (40) above. Specifically, first, a reaction vessel was purged with argon gas, and palladium hydroxide-activated carbon (Pd 20%, approximately 50% water content) (150 mg) was added to an isopropanol (7.0 mL) solution of 9-benzyl-9-azabicyclo[3.3.1]nonene (1.50 g, 7.00 mmol) at room temperature. The reaction vessel was then filled with hydrogen gas (1 atm), and the mixture was stirred at room temperature for 40 hours. The reaction vessel was then purged with argon gas, and the reaction solution was filtered through Celite. The resulting filtrate was concentrated under reduced pressure to give 9-azabicyclo[3.3.1]nonane as a white solid (880 mg). This compound was used in the subsequent reaction without purification. Next, to a solution of the obtained white solid (880 mg) in methanol (18 mL) were added acetic acid (0.84 mL, 14.1 mmol) and sodium nitrite (1.21 g, 17.6 mmol) at room temperature. This solution was stirred at room temperature for 10 hours and then at 50°C for an additional 14 hours. After that, it was cooled to room temperature, and organic matter was extracted from the aqueous layer with diethyl ether. The organic layer was washed with saturated brine, dried over sodium sulfate, and concentrated under reduced pressure. The obtained residue was purified by silica gel column chromatography to obtain a yellow solid of 9-nitroso-9-azabicyclo[3.3.1]nonane (842 mg, 78% (two steps)) as a hexane-ethyl acetate (5:1 volume ratio) eluate.

[0202] Regarding the 9-nitroso-9-azabicyclo[3.3.1]nonane obtained below: １ H-NMR, １３ The results of C-NMR, IR, MS, and HRMS (EI) are shown below.

[0203] １ H-NMR (400MHz): δ 5.31-5.24 (m, 1H), 4.85 (s, 1H), 2.29-1.87 (m, 7H), 1.80-1.55 (m, 5H). １３ C-NMR (100MHz): δ 54.3, 43.2, 31.2, 29.2, 20.0. IR(neat[cm －１ ]): 2947, 2916, 2854, 1423, 1369, 1277, 1192, 1111, 1018, 914, 733. MS [m / z]: 154 (M ＋ ), 96 (100%). HRMS (EI): Calcd. for C ８ H １４ N ２ O:154.1106, found:154.1106.

[0204] <Synthesis of 9-azabicyclo[3.3.1]nonan-9-amine>

[0205]

[0206] 9-Azabicyclo[3.3.1]nonane-9-amine was synthesized according to the reaction pathway shown in the above formula (41). That is, first, a solution of LAH (148 mg, 3.89 mmol) in diethyl ether (7.0 mL) was added to a solution of 9-nitroso-9-azabicyclo[3.3.1]nonane (400 mg, 2.59 mmol) in diethyl ether (Et ２ ​A solution of 9-azabicyclo[3.3.1]nonan-9-amine (6.0 mL) was added portionwise at 0°C. This solution was stirred at room temperature for 24 hours, and then diethyl ether, water, and 10% sodium hydroxide solution were slowly added at 0°C, followed by stirring at room temperature for 30 minutes. The mixture was then filtered through Celite and concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography to give a white solid of 9-azabicyclo[3.3.1]nonan-9-amine (181 mg, 50%) as a chloroform-methanol (1:1 volume ratio) eluate.

[0207] Regarding the 9-azabicyclo[3.3.1]nonane-9-amine obtained below: １ H-NMR, １３ The results of C-NMR, IR, MS, and HRMS (EI) are shown below.

[0208] １ H-NMR (400MHz): δ 2.95 (s, 2H), 2.17-2.06 (m, 5H), 1.98-1.85 (m, 3H), 1.60-1.52 (m, 6H). １３ C-NMR (100MHz): δ 55.8, 19.7. IR(neat[cm －１ ]): 3323, 2923, 1608, 1454, 1312, 1122, 1041, 897, 801. MS [m / z]: 140 (M ＋ ), 97 (100%). HRMS (EI): Calcd. for C ８ H １６ N ２ :140.1313, found:140.1307.

[0209] <Synthesis of DAND>

[0210]

[0211] ​DAND was synthesized according to the reaction pathway shown in formula (42) above. Specifically, copper iodide (20.4 mg, 107 μmol) and 2,2'-bipyridine (20.0 mg, 128 μmol) were first dissolved in acetonitrile (5 mL). An acetonitrile solution (6 mL) of the previously synthesized 9-azabicyclo[3.3.1]nonan-9-amine (150 mg, 1.07 mmol) was slowly added dropwise to the solution over 2.5 hours at room temperature. After stirring for 18 hours at room temperature in the open air, tetramethylethylenediamine (32 μL, 0.21 mmol) was added and stirred for 10 minutes. Water was added to the solution, and organic matter was extracted from the aqueous layer with dichloromethane. The organic layer was further washed with saturated saline, dried over sodium sulfate, and concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography to give DAND (88 mg, 0.32 mmol, yield 60%) as a white solid as an eluate of hexane-ethyl acetate (20:1 volume ratio).

[0212] The following DAND １ H-NMR, １３ The results of C-NMR, IR, MS, and HRMS (EI) are shown below.

[0213] １ H-NMR (400MHz): δ 4.04 (s, 4H), 2.15-1.95 (m, 12H), 1.66-1.56 (m, 12H). １３ C-NMR (100MHz): δ 50.4, 28.2, 20.8. IR(neat[cm －１ ]): 2927, 2846, 1435, 1371, 1304, 1248, 1078, 1012, 928, 895, 804, 752. MS [m / z]: 276 (M ＋ ), 96 (100%). HRMS (EI): Calcd. for C １６ H ２８ N ４ :276.2314, found:276.2326.

[0214] (Example 10) <Synthesis of DAND Radical Salt (BArF Salt)>

[0215] ​

[0216] A DAND radical salt (BArF salt) represented by the following chemical formula (44) was synthesized according to the reaction pathway shown in the above formula (43). The starting material, DAND represented by the above chemical formula (39), was synthesized according to the reaction pathway shown in the above formula (38).

[0217]

[0218] <Synthesis of DAND Radical Salt (BArF Salt)> According to the reaction pathway shown in the above formula (43), the DAND radical salt (BArF Salt) represented by the above chemical formula (44) was synthesized. That is, first, chlorine gas was bubbled into a carbon tetrachloride (3.0 mL) solution of DAND (80 mg, 0.29 mmol) at room temperature (chlorine gas was generated freshly by adding concentrated hydrochloric acid dropwise to manganese dioxide under heated conditions). Thereafter, the precipitated red solid was collected by filtration and washed with carbon tetrachloride. The obtained red solid was dried under reduced pressure for 2 hours to obtain a red solid (88 mg) of DAND radical salt (chloride). This compound was used in the next reaction without purification. Next, sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate hydrate (275 mg, 0.31 mmol) was added to a solution of DAND radical salt (chloride) (88 mg) in tetrahydrofuran (3.0 mL) at room temperature. This solution was stirred at room temperature for 2 hours, and then water was added. Organic matter was extracted from the aqueous layer with dichloromethane. The organic layer was dried over sodium sulfate and concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography to obtain a red solid of DAND radical salt (BArF salt) (100 mg, 87.7 μmol, 30% (2 steps)) as a chloroform-methanol (20:1 volume ratio) eluate.

[0219] The results of elemental analysis of the obtained DAND radical salt (BArF salt) are shown below.

[0220] Anal. Calcd. for C ４８ H ４０ BF ２４ N ４ ・ :for C, 50.59; H, 3.54; N, 4.92; found: C, 50.08; H, 3.66; N, 4.86.

[0221] Example 11 Synthesis of 1,2-bis(3-((tert-butyldimethylsilyl)oxy)-9-azabicyclo[3.3.1]nonan-9-yldiazene

[0222]

[0223] According to the reaction pathway shown in the above formula (45), 1,2-bis(3-((tert-butyldimethylsilyl)oxy)-9-azabicyclo[3.3.1]nonan-9-yldiazene (hereinafter, tert-butyldimethylsilyl will be referred to as "TBS" and 1,2-bis(3-((tert-butyldimethylsilyl)oxy)-9-azabicyclo[3.3.1]nonan-9-yldiazene will be referred to as "3-TBSoxy-DAND"), which is represented by the following chemical formula (46), was synthesized. The starting material, (3r)-9-benzyl-9-azabicyclo[3.3.1]-3-nonanol, was synthesized based on WO 2007 / 039563.

[0224] <Synthesis of 9-benzyl-3-TBSoxy-9-azabicyclo[3.3.1]nonane>

[0225]

[0226] 9-Benzyl-3-TBSoxy-9-azabicyclo[3.3.1]nonane was synthesized according to the reaction pathway shown in formula (46) above. Specifically, first, imidazole (1.64 g, 24.1 mmol) and TBS chloride (2.18 g, 14.5 mmol) were added to a dichloromethane (60 mL) solution of (3r)-9-benzyl-9-azabicyclo[3.3.1]-3-nonanol (2.79 g, 12.1 mmol) at room temperature, followed by stirring at room temperature for 11 hours. Water was then added at room temperature, and organic matter was extracted from the aqueous layer with dichloromethane. The organic layer was washed with saturated saline, dried over magnesium sulfate, and concentrated under reduced pressure. The obtained residue was purified by silica gel column chromatography to obtain 9-benzyl-3-TBSoxy-9-azabicyclo[3.3.1]nonane (3.95 g, 11.4 mmol, 95%) as a colorless liquid as a hexane-ethyl acetate (15:1 volume ratio) eluate.

[0227] Regarding the 9-benzyl-3-TBSoxy-9-azabicyclo[3.3.1]nonane obtained below: １ H-NMR, １３ The results of C-NMR, IR, MS, and HRMS (EI) are shown below.

[0228] １ H-NMR (400MHz): δ 7.30-7.20 (m, 4H), 7.18-7.12 (m, 1H), 4.14 (tt, J=6.8, 6.8Hz, 1H), 3 .71 (s, 2H), 2.93-2.84 (m, 2H), 2.31 (dtd, J=18.7, 13.4, 5.1Hz, 1H), 2.19 (ddd, J=15.0, 9.1, 6.6Hz), 1.84 (tt, J=13.4, 4.9Hz, 2H), 1.43- 1.34 (m, 1H), 1.31 (ddd, J=13.9, 7.1, 2.5Hz, 2H), 1.07-1.04 (m, 2H). １３ C-NMR (100MHz): δ 140.7, 128.2, 128.1, 126.6, 64.5, 56.1, 49.935.8, 25.9, 25.3, 18.2, 14.8, -4.7. IR(neat[cm －１ ]): 2929, 1090, 1032, 835, 775. MS [m / z]: 345 [M ＋ ], 91 [100%]. HRMS (EI): Calcd. for C ２１ H ３５ NOSi:345.2488, found:345.2419.

[0229] <Synthesis of 3-TBSoxy-9-nitroso-9-azabicyclo[3.3.1]nonane>

[0230]

[0231] ​3-TBSoxy-9-nitroso-9-azabicyclo[3.3.1]nonane was synthesized according to the reaction pathway shown in formula (47) above. Specifically, first, palladium(II) hydroxide (20% Pd, approximately 50% water content) (55 mg) was added to a solution of 9-benzyl-3-TBSoxy-9-azabicyclo[3.3.1]nonane (299 mg, 865 μmol) in ethanol (1.7 mL) in a reaction vessel purged with argon gas at room temperature. The vessel was then filled with hydrogen gas (1 atm) and stirred at room temperature for 28 hours. The reaction vessel was then purged with argon gas, and the reaction solution was filtered through Celite. The resulting filtrate was concentrated under reduced pressure. The resulting residue was diluted with chloroform, dried over potassium carbonate, and concentrated under reduced pressure to give 3-TBSoxy-9-azabicyclo[3.3.1]nonane (174 mg) as a pale yellow oil. This compound was used in the next reaction without purification. Next, to a solution of the obtained pale yellow oil (174 mg) in water (1.4 mL) were added acetic acid (58.3 μL, 1.02 mmol) and sodium nitrite (469 mg, 6.79 mmol) at room temperature. This solution was stirred at 70°C for 2 hours, then cooled to room temperature, and organic matter was extracted from the aqueous layer with diethyl ether. The organic layer was washed with saturated brine, dried over sodium sulfate, and concentrated under reduced pressure. The obtained residue was purified by silica gel column chromatography to give a yellow solid of 3-TBSoxy-9-nitroso-9-azabicyclo[3.3.1]nonane (121 mg, 49% (two steps)) as a hexane-ethyl acetate (5:1 volume ratio) eluate.

[0232] Regarding the 3-TBSoxy-9-nitroso-9-azabicyclo[3.3.1]nonane obtained below: １ H-NMR, １３ The results of C-NMR, IR, MS, and HRMS (EI) are shown below.

[0233] １ ​H-NMR (400MHz): δ 5.34 (d, J=5.5Hz, 1H), 4.95 (d, J=6.3Hz, 1H), 3.59-3.51 (m, 1H), 2.50-2.32 (m, 2H), 2.09 (dddd , J=13.7, 9.9, 6.3, 1.9Hz, 1H), 1.85-1.46 (m, 7H), 0.87 (d, J=2.2Hz, 9H), 0.02 (d, J=2.9Hz, 6H). １３ C-NMR (100MHz): δ 63.6, 52.9, 41.7, 37.0.35.2, 32.2, 29.9, 25.7, 17.9, 14.6, -4.9. IR(neat[cm －１ ]): 2931, 2856, 1435, 1367, 1103. MS [m / z]: 284 [M ＋ ], 227 [100%]. HRMS (EI): Calcd. for C １４ H ２８ N ２ O ２ Si:284.1920, found:284.1913.

[0234] <Synthesis of 3-TBSoxy-DAND>

[0235]

[0236] 3-TBSoxy-DAND was synthesized according to the reaction pathway shown in the above formula (48). That is, first, a solution of LAH (24 mg, 637 μmol) in diethyl ether (708 μL) was added to a solution of 3-TBSoxy-9-nitroso-9-azabicyclo[3.3.1]nonane (121 mg, 425 μmol) in diethyl ether (Et ２A solution of 3-TBSoxy-9-azabicyclo[3.3.1]nonan-9-amine (708 μL) was added portionwise at 0°C. This solution was stirred at room temperature for 3 hours, and then diethyl ether (1.4 mL) was added and stirred for 5.5 hours. Diethyl ether (2.8 mL) was then added and stirred for 17.5 hours. Diethyl ether, water, and 10% sodium hydroxide solution were then slowly added at 0°C, and the mixture was stirred at room temperature for 15 minutes. The mixture was then filtered through Celite and concentrated under reduced pressure to obtain a white solid (94 mg) containing 3-TBSoxy-9-azabicyclo[3.3.1]nonan-9-amine. This compound was used in the next reaction without purification. Next, copper iodide (12.3 mg, 64.4 μmol) and 2,2'-bipyridine (10.6 mg, 64.4 μmol) were dissolved in acetonitrile (1.5 mL). To this solution, a solution of the previously synthesized white solid (87 mg) containing 3-TBSoxy-9-azabicyclo[3.3.1]nonan-9-amine in acetonitrile (1.8 mL) was slowly added dropwise over 3 hours. After stirring for 14 hours at room temperature in the open air, tetramethylethylenediamine (19 μL, 129 μmol) was added and stirred for 10 minutes. Water was added to the solution, and organic matter was extracted from the aqueous layer with dichloromethane. The organic layer was further washed with saturated brine, dried over sodium sulfate, and concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography to obtain a white solid of 3-TBSoxy-DAND (13.6 mg, 25.2 μmol, 12% yield (two steps)) as a hexane-ethyl acetate (30:1 volume ratio to 15:1 volume ratio) eluate.

[0237] Regarding the 3-TBSoxy-DAND obtained below, １ H-NMR, １３ The results of C-NMR, IR, MS, and HRMS (EI) are shown below.

[0238] １ H-NMR (400MHz): δ 4.25-4.17 (m, 4H), 3.91-3.80 (m, 2H), 2.36-2.17 (m, 6H), 1.75 (t, J=23Hz, 4H), 1.56-1.35 (m, 10H), 0.88 (s, 18H), 0.03 (s, 12H). １３ ​C-NMR (100 MHz): δ -4.8, 0.0, 14.8, 18.1, 25.9, 29.0, 35.2, 49.2, 64.2. IR(neat[cm －１ ]): 3394, 2931, 1066, 773. MS [m / z]: 536 [M ＋ , 100%]. HRMS (EI): Calcd. for C ２８ H ５６ N ４ O ２ Si ２ :536.3942, found:536.3943.

[0239] (Example 12) <Synthesis of 1,2-di(8-azabicyclo[3.2.1]octan-8-yl)diazene>

[0240]

[0241] According to the reaction pathway shown in the above formula (49), 1,2-di(8-azabicyclo[3.2.1]octan-8-yl)diazene (hereinafter referred to as "DAOD") represented by the following chemical formula (50) was synthesized. The starting material, benzyl-8-azabicyclo[3.2.1]octene-8-carboxylate, was synthesized by the method reported by Toda et al. (Toda, M. et al., J. Org. Chem., 2023, Vol. 88, No. 3, pp. 1434-1444).

[0242]

[0243] <Synthesis of 8-nitroso-8-azabicyclo[3.2.1]octane>

[0244]

[0245] 8-Nitroso-8-azabicyclo[3.2.1]octane was synthesized according to the reaction pathway shown in formula (51) above. Specifically, first, a reaction vessel was purged with argon gas, and palladium hydroxide-activated carbon (Pd 20%, approximately 50% water content) (143 mg) was added to an acetonitrile (29 mL) solution of benzyl-8-azabicyclo[3.2.1]octene-8-carboxylate (1.43 g, 5.88 mmol) at room temperature. The reaction vessel was then filled with hydrogen gas (1 atm), and the mixture was stirred at room temperature for 12 hours. The reaction vessel was then purged with argon gas, and the reaction solution was filtered through Celite. The resulting filtrate was concentrated under reduced pressure to yield a white solid, 8-azabicyclo[3.2.1]octane (697 mg). This compound was used in the subsequent reaction without purification. Next, to a solution of the obtained white solid (697 mg) in water (13 mL) were added acetic acid (0.56 mL, 9.4 mmol) and sodium nitrite (4.32 g, 62.7 mmol) at room temperature. This solution was stirred at 70°C for 20 hours, then cooled to room temperature, and organic matter was extracted from the aqueous layer with diethyl ether. The organic layer was washed with saturated brine, dried over sodium sulfate, and concentrated under reduced pressure. The obtained residue was purified by silica gel column chromatography to obtain a yellow solid of 8-nitroso-8-azabicyclo[3.2.1]octane (479 mg, 3.07 mmol, 58% (2 steps)) as a hexane-ethyl acetate (5:1 volume ratio) eluate.

[0246] Regarding the 8-nitroso-8-azabicyclo[3.2.1]octane obtained below: １ H-NMR, １３ The results of C-NMR, IR, MS, and HRMS (EI) are shown below.

[0247] １ H-NMR (400MHz): δ 5.13-5.06 (m, 1H), 4.93 (d, J = 7.2Hz, 1H), 2.24-2.10 (m, 1H), 2.00-1.45 (m, 9H). １３ C-NMR (100MHz): δ 58.4, 50.6, 34.2, 30.4, 26.1, 25.5, 16.3. IR(neat[cm －１ ​]): 2942, 2880, 1476, 1405, 1347, 1280, 730. MS [m / z]: 140 (M ＋ ), 110 (100%). HRMS (EI): Calcd. for C ７ H １２ N ２ O:140.1860, found:140.0956.

[0248] <Synthesis of DAOD>

[0249]

[0250] DAOD was synthesized according to the reaction pathway shown in the above formula (52). That is, first, a solution of LAH (109 mg, 2.88 mmol) in diethyl ether (13 mL) was added to a solution of 8-nitroso-8-azabicyclo[3.2.1]octane (300 mg, 1.92 mmol) in diethyl ether (Et ２ A solution of 8-azabicyclo[3.2.1]octan-8-amine (6.0 mL) was added portionwise at 0°C. After stirring this solution at room temperature for 1 hour, diethyl ether, water, and 10% sodium hydroxide solution were slowly added at 0°C, and the mixture was stirred at room temperature for 30 minutes. The mixture was then filtered through Celite and concentrated under reduced pressure to obtain 8-azabicyclo[3.2.1]octan-8-amine (262 mg) as a white solid. This product was used in the next reaction without purification. Next, copper iodide (39.5 mg, 208 μmol) and 2,2'-bipyridine (38.9 mg, 249 μmol) were dissolved in acetonitrile (8 mL). To this solution, the previously synthesized 8-azabicyclo[3.2.1]octan-8-amine (262 mg) in acetonitrile (12 mL) was slowly added dropwise over 7 hours at room temperature. After stirring for 17 hours at room temperature in the open air, tetramethylethylenediamine (62 μL, 415 μmol) was added and stirred for 10 minutes. Water was added to the solution, and organic matter was extracted from the aqueous layer with dichloromethane. The organic layer was further washed with saturated brine, dried over sodium sulfate, and concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography to obtain a white solid of DAOD (183 mg, 737 μmol, yield 77% (two steps)) as a eluate of hexane-ethyl acetate (15:1 volume ratio).

[0251] The following DAODs are obtained: １ H-NMR, １３ The results of C-NMR, IR, MS, and HRMS (EI) are shown below.

[0252] １ H-NMR (400MHz): δ 4.16 (s, 4H), 1.91-1.37 (m, 20H). １３ C-NMR (100MHz): δ 58.1, 57.9, 29.7, 26.4, 16.9. IR(neat[cm －１ ]): 2942, 2868, 1445, 1335, 1231, 1016, 967, 951, 755. MS [m / z]: 248 (M ＋ ), 110 (100%). HRMS (EI): Calcd. for C １４ H ２４ N ４ :248.2001, found:248.2007.

[0253] <Activity Evaluation 1> Using the DAD obtained in Example 1 as a catalyst, an oxidation reaction of alcohol was carried out according to the reaction pathway shown in the following formula (53).

[0254]

[0255] According to the reaction pathway shown in the above formula (53), oxidation reactions were carried out on various alcohols. Specifically, the alcohols shown in Table 1 (substrate, 1.00 mmol), DAD (1.50 mg, 5 μmol), sodium bicarbonate (NaHCO ３ , 420 mg, 5.00 mmol) in dichloromethane (CH ２ Cl ２ ​, 5.0 mL) and stirred under ice-cooling. Next, trichloroisocyanuric acid (chemical formula (54) below, hereinafter referred to as TCCA, 116 mg, 0.500 mmol) was added to the reaction solution, and the mixture was stirred at the same temperature. After confirming the completion of the reaction, 20% aqueous sodium thiosulfate solution was added to the reaction solution, and the mixture was extracted with dichloromethane. The obtained organic layer was dried over sodium sulfate and then concentrated under reduced pressure. The residue was purified by silica gel column chromatography to obtain the target compound (product, yield 74% to 94%). In Table 1, a indicates the addition of 5 mol% DAD relative to the alcohol, and b indicates the NMR yield. Ph indicates a phenyl group, TBS indicates a tert-butyldimethylsilyl group, and Cbz indicates a benzyloxycarbonyl group.

[0256]

[0257]

[0258] As is clear from the results shown in Table 1, it was confirmed that the alcohol oxidation catalyst containing the DAD of the present invention functions as an oxidation catalyst for various alcohols and can produce the target compound, aldehyde or ketone, corresponding to each alcohol in high yield. Furthermore, the target compound was obtained in high yield even from alcohols with sterically bulky and complex structures, and it was confirmed that not only simple benzyl alcohol and aliphatic alcohols but also a wide range of alcohols, such as alcohols containing heteroatoms and sugar alcohols, can be oxidized as substrates.

[0259] <Activity Evaluation 2> Using the DAD obtained in Example 1 as a catalyst, an oxidation reaction of alcohol was carried out according to the reaction pathway shown in the following formula (55).

[0260]

[0261] According to the reaction pathway shown in the above formula (55), oxidation reactions were carried out on various alcohols. Specifically, the alcohols shown in Table 2 (substrate, 1.00 mmol), DAD (300 μg, 1.00 μmol), and potassium bromide (KBr, 11.9 mg, 0.100 mmol) were dissolved in dichloromethane (CH ２ ​Cl ２ , 2.5 mL), and then 1.25 mL of saturated aqueous sodium bicarbonate was added and stirred under ice cooling. Next, a mixed solution of 1.54 mol / L sodium hypochlorite (1.0 mL, 1.5 mmol) and saturated aqueous sodium bicarbonate (1.25 mL) was slowly added to the reaction solution and stirred at the same temperature. Isopropanol was then added to the reaction solution and stirred for 10 minutes. The reaction solution was extracted with dichloromethane, and the resulting organic layer was washed with saturated brine. The resulting organic layer was dried over sodium sulfate and then concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography to obtain the target compound (product, yield 85-98%). In Table 2, a indicates a reaction time of 1 hour, b indicates that 0.5 mol% DAD was added relative to the alcohol, and c indicates that 1.2 equivalents of sodium hypochlorite were used. Here, Bz represents a benzoyl group, TBS represents a tert-butyldimethylsilyl group, and Cbz represents a benzyloxycarbonyl group.

[0262]

[0263] <Activity Evaluation 3> Using the DAD radical salt (BArF salt) obtained in Example 2 as a catalyst, an oxidation reaction of menthol was carried out according to the reaction pathway shown in the following formula (56).

[0264]

[0265] Menthol (40 mg, 0.26 mmol), DAD radical salt (BArF salt or DAD-BArF) (1.5 mg, 1.3 μmol), sodium bicarbonate (NaHCO ３ , 110 mg, 1.30 mmol) in dichloromethane (CH ２ Cl ２ The reaction mixture was dissolved or suspended in 1.3 mL of toluene (Chemical Formula (54), 30 mg, 0.13 mmol) and stirred under ice cooling. TCAA (Chemical Formula (54), 30 mg, 0.13 mmol) was then added to the reaction mixture, and the mixture was allowed to react at the same temperature for 6 hours. 10 μL of the reaction mixture after the reaction was then taken and diluted with 0.5 mL of isopropanol to prepare a sample, which was then analyzed by gas chromatography. As a result, the conversion rate reached 89% 6 hours after the start of the reaction.

[0266] As is clear from the above results, it was confirmed that the alcohol oxidation catalyst containing the DAD radical salt (BArF salt) of the present invention functions as an oxidation catalyst for alcohols and can produce, as the target compound, a ketone corresponding to the alcohol in high yield.

[0267] <Activity Evaluation 4> Using the DAD obtained in Example 1 as a catalyst, an oxidation reaction of alcohol was carried out according to the reaction pathway shown in the following formula (57).

[0268]

[0269] In the same manner as in Activity Evaluation 1, except that 1,3-dichloro-5,5-dimethylhydantoin (101 mg, 0.512 mmol) represented by the following chemical formula (58) was used instead of TCAA, an oxidation reaction of menthol represented by the above formula (57) was carried out. The stirring time under ice cooling was set to 6 hours. The reaction was evaluated by gas chromatography, and the production of the target compound (conversion rate 33%) was confirmed.

[0270]

[0271] <Activity Evaluation 5> An oxidation reaction of menthol represented by the above formula (57) was carried out in the same manner as in Activity Evaluation 1, except that 1,3-dibromo-5,5-dimethylhydantoin (146 mg, 0.512 mmol) represented by the following chemical formula (59) was used instead of TCAA. The stirring (reaction) time under ice cooling was set to 6 hours. The reaction was evaluated by gas chromatography, and the production of the target compound (conversion rate 43%) was confirmed.

[0272]

[0273] <Activity Evaluation 6> An oxidation reaction of menthol represented by the above formula (57) was carried out in the same manner as in Activity Evaluation 1, except that N-chlorosaccharin (245 mg, 1.13 mmol) represented by the following chemical formula (60) was used instead of TCAA. The stirring (reaction) time under ice cooling was set to 6 hours. The reaction was evaluated by gas chromatography, and the production of the target compound (conversion rate 39%) was confirmed.

[0274]

[0275] As is clear from the above results, it was confirmed that the alcohol oxidation catalyst containing the DAD of the present invention functions as an oxidation catalyst for alcohols even when the co-oxidant is changed, and that the target compound, an aldehyde or ketone corresponding to each alcohol, can be obtained in high yield.

[0276] <Activity Evaluation 7> <Comparison of Alcohol Oxidation Catalyst Activity Due to Differences in Main Skeleton and Substituent> As shown in the reaction pathway shown in the following formula (61), an alcohol oxidation reaction was carried out using sodium hypochlorite as an oxidant and menthol as a substrate. That is, menthol (156 mg, 1.00 mmol), a catalyst (0.1 mol%) shown in Table 3, and potassium bromide (KBr, 11 mg, 10.0 mol%) were dissolved in dichloromethane (CH ２ Cl ２ The reaction mixture was dissolved in a mixed solution of 1.54 mol / L sodium hypochlorite aqueous solution (1.0 mL, 1.5 mmol) and saturated sodium bicarbonate aqueous solution (1.25 mL) and stirred under ice cooling. A mixed solution of 1.54 mol / L sodium hypochlorite aqueous solution (1.0 mL, 1.5 mmol) and saturated sodium bicarbonate aqueous solution (1.25 mL) was slowly added dropwise to the reaction mixture and stirred at the same temperature. Next, 10 μL of the reaction mixture (dichloromethane layer) was taken and diluted with 0.5 mL of isopropanol to prepare a sample. The conversion rate of this sample was evaluated using gas chromatography 30 minutes after the start of the reaction.

[0277]

[0278]

[0279] As is clear from the above results, it has been confirmed that the tetrazene-type alcohol oxidation catalyst of the present invention functions as an oxidation catalyst for alcohols even when the main skeleton and substituents are changed, and that the target compound, an aldehyde or ketone corresponding to each alcohol, can be obtained in high yield.

[0280] <Comparison of catalytic current by cyclic voltammetry (CV)> The catalytic current of DAD obtained in Example 1 was compared with that of AZADO using cyclic voltammetry (CV). The measurement conditions for cyclic voltammetry were as follows: Tetrabutylammonium hexafluorophosphate (TBAPF ６ , 387 mg, 1.00 mmol), DAD or AZADO (10 μmol) was dissolved in acetonitrile (CH ３ The anode was made of glassy carbon, the cathode was made of platinum wire, and the reference electrode was made of Ag / AgNO. ３ Measurements were performed using an electrode at a sweep rate of 10 mV / s. Subsequently, menthol (156 mg, 1.00 mmol) and 2,4,6-collidine (66 μL, 0.50 mmol) were added, and measurements were performed again under the same conditions. The results are shown in FIGS. 1 and 2. FIG. 1 shows the results of cyclic voltammetry measurements of DAD. In FIG. 1, the dashed line shows the cyclic voltammetry of DAD, and the solid line shows the cyclic voltammetry when DAD was used as an oxidation catalyst for menthol. FIG. 2 shows the results of cyclic voltammetry measurements of AZADO. In FIG. 2, the dashed line shows the cyclic voltammetry of AZADO, and the solid line shows the cyclic voltammetry when AZADO was used as an oxidation catalyst for menthol. From the results shown in Figure 1, it was found that the difference (Δip) between the oxidation current in cyclic voltammetry of DAD and the oxidation current in cyclic voltammetry when DAD was used as the menthol oxidation catalyst was 9.49 μA. On the other hand, from the results shown in Figure 2, it was found that the difference (Δip) between the oxidation current in cyclic voltammetry of AZADO and the oxidation current in cyclic voltammetry when AZADO was used as the menthol oxidation catalyst was 3.74 μA. From these results, it was found that when menthol was used as the alcohol, DAD exhibited a larger catalytic current than AZADO. This suggests that the rate of the menthol oxidation reaction by DAD is higher than the rate of the menthol oxidation reaction by AZADO.

[0281] As described above, the present invention provides novel tetrazene compounds, tetrazene radical salt compounds, tetrazene-type alcohol oxidation catalysts, and tetrazene radical salt-type alcohol oxidation catalysts that are suitable for use as alcohol oxidation catalysts capable of exhibiting sufficiently high oxidation catalytic activity for primary and secondary alcohols and that are easy to produce. Therefore, the present invention is highly useful because it can be applied to catalytic alcohol oxidation reactions, which are a means for environmentally friendly synthesis of high-value-added organic compounds, such as those used in pharmaceuticals, pharmaceutical raw materials, pesticides, cosmetics, and organic materials.

Claims

1. A tetrazene compound having an adamantane skeleton represented by the following chemical formula (1) or a bicyclo skeleton represented by the following chemical formula (2). (In formula (1), n ​​is 0 or 1, and R １ is H, an alkyl group having 1 to 6 carbon atoms which may have a substituent, a phenyl group which may have a substituent, a carboxy group, an amide group, or an alkoxycarbonyl group having 1 to 6 carbon atoms; R ２ is H, an alkyl group having 1 to 6 carbon atoms which may have a substituent, a carboxy group, an amide group, or an alkoxycarbonyl group having 1 to 6 carbon atoms; X １ is H, OR ３ (R ３ represents H, an optionally substituted alkyl group having 1 to 6 carbon atoms, an acyl group, or a optionally substituted silyl group having 3 to 18 carbon atoms), NR ４ R ５ (R ４ , R ５ each independently represents H, an optionally substituted alkyl group having 1 to 6 carbon atoms, an acyl group, an alkoxycarbonyl group, or a group in which the OH of a sulfo group is substituted with a monovalent group; R ４ and R ５ may be bonded to form a ring), a halogen atom, a phenyl group which may have a substituent, or an alkyl group having 1 to 6 carbon atoms which may have a substituent; ２ is H, OR ３ (R ３ represents H, an optionally substituted alkyl group having 1 to 6 carbon atoms, an acyl group, or a optionally substituted silyl group having 3 to 18 carbon atoms), NR ４ R ５ (R ４ , R ５ each independently represents H, an optionally substituted alkyl group having 1 to 6 carbon atoms, an acyl group, an alkoxycarbonyl group, or a group in which the OH of a sulfo group is substituted with a monovalent group; R ４ and R ５ may be bonded to form a ring), or a halogen atom. １ and X ２ Either of these is H.) (In formula (2), n is 0 or 1, R ６ , R ７ are each independently H or an alkyl group having 1 to 6 carbon atoms which may have a substituent; X ３ , X ４ each independently represents H, an alkyl group having 1 to 6 carbon atoms which may have a substituent, an aromatic group which may have a substituent, OR ３ (R ３ represents H, an optionally substituted alkyl group having 1 to 6 carbon atoms, an acyl group, or a optionally substituted silyl group having 3 to 18 carbon atoms), NR ４ R ５ (R ４ , R ５ each independently represents H, an optionally substituted alkyl group having 1 to 6 carbon atoms, an acyl group, an alkoxycarbonyl group, or a group in which the OH of a sulfo group is substituted with a monovalent group; R ４ and R ５ may be bonded to form a ring), or a halogen atom, or X ３ and X ４ is a keto group, an imino group (NR ８ ), oxime group (NOR ９ ), or a hydrazone group (NNR １０ R １１ ), and the R ８ ~R １１ each independently represents H, an alkyl group having 1 to 6 carbon atoms which may have a substituent, a phenyl group which may have a substituent, an acyl group, an alkoxycarbonyl group, or a group in which the OH of a sulfo group has been substituted with a monovalent group; R １０ and R １１ may be bonded to form a ring. ３ and X ４ may be bonded to form a ring. ６ , R ７ , X ３ , X ４ None of the above are H.) 2. A tetrazene radical salt compound having an adamantane skeleton represented by the following chemical formula (3) or a bicyclo skeleton represented by the following chemical formula (4). (In formula (3), n is 0 or 1, and R １ is H, an alkyl group having 1 to 6 carbon atoms which may have a substituent, a phenyl group which may have a substituent, a carboxy group, an amide group, or an alkoxycarbonyl group having 1 to 6 carbon atoms; R ２ is H, an alkyl group having 1 to 6 carbon atoms which may have a substituent, a carboxy group, an amide group, or an alkoxycarbonyl group having 1 to 6 carbon atoms; X １ is H, OR ３ (R ３ represents H, an optionally substituted alkyl group having 1 to 6 carbon atoms, an acyl group, or a optionally substituted silyl group having 3 to 18 carbon atoms), NR ４ R ５ (R ４ , R ５ each independently represents H, an optionally substituted alkyl group having 1 to 6 carbon atoms, an acyl group, an alkoxycarbonyl group, or a group in which the OH of a sulfo group is substituted with a monovalent group; R ４ and R ５ may be bonded to form a ring), a halogen atom, a phenyl group which may have a substituent, or an alkyl group having 1 to 6 carbon atoms which may have a substituent; ２ is H, OR ３ (R ３ represents H, an optionally substituted alkyl group having 1 to 6 carbon atoms, an acyl group, or a optionally substituted silyl group having 3 to 18 carbon atoms), NR ４ R ５ (R ４ , R ５ each independently represents H, an optionally substituted alkyl group having 1 to 6 carbon atoms, an acyl group, an alkoxycarbonyl group, or a group in which the OH of a sulfo group is substituted with a monovalent group; R ４ and R ５ may be bonded to form a ring), or a halogen atom. １ and X ２ Either of the two is H. Y － is a monovalent anion.) (In formula (4), n is 0 or 1, R ６ , R ７ are each independently H or an alkyl group having 1 to 6 carbon atoms which may have a substituent; X ３ , X ４ each independently represents H, an alkyl group having 1 to 6 carbon atoms which may have a substituent, an aromatic group which may have a substituent, OR ３ (R ３ represents H, an optionally substituted alkyl group having 1 to 6 carbon atoms, an acyl group, or a optionally substituted silyl group having 3 to 18 carbon atoms), NR ４ R ５ (R ４ , R ５ each independently represents H, an optionally substituted alkyl group having 1 to 6 carbon atoms, an acyl group, an alkoxycarbonyl group, or a group in which the OH of a sulfo group is substituted with a monovalent group; R ４ and R ５ may be bonded to form a ring), or a halogen atom, or X ３ and X ４ is a keto group, an imino group (NR ８ ), oxime group (NOR ９ ), or a hydrazone group (NNR １０ R １１ ), and the R ８ ~R １１ each independently represents H, an alkyl group having 1 to 6 carbon atoms which may have a substituent, a phenyl group which may have a substituent, an acyl group, an alkoxycarbonyl group, or a group in which the OH of a sulfo group has been substituted with a monovalent group; R １０ and R １１ may be bonded to form a ring. ３ and X ４ may be bonded to form a ring. － is a monovalent anion.) 3. Y in the chemical formula (3) or (4) － The tetrazene radical salt compound of claim 2 , wherein:

4. A tetrazene-type alcohol oxidation catalyst for oxidizing alcohol, comprising at least one selected from the group consisting of the tetrazene compound and its derivatives according to claim 1.

5. A tetrazene radical salt type alcohol oxidation catalyst for oxidizing alcohol, comprising at least one selected from the group consisting of the tetrazene radical salt compound and its derivatives according to claim 2.

6. An alcohol oxidation catalyst for oxidizing alcohol, comprising a tetrazene compound having a bicyclo skeleton represented by the following chemical formula (5): (In the formula, n is 0 or 1.) 7. A method for oxidizing an alcohol, which comprises oxidizing an alcohol in the presence of the tetrazene-type alcohol oxidation catalyst according to claim 4 and a co-oxidant.

8. The method for oxidizing an alcohol according to claim 7, wherein the alcohol is a primary alcohol or a secondary alcohol.

9. The method for oxidizing alcohol according to claim 7 or 8, wherein the amount of the tetrazene-type alcohol oxidation catalyst added is 0.01 mole or more and 100 moles or less per 100 moles of all hydroxy groups in the alcohol.

10. A method for oxidizing an alcohol, which comprises oxidizing an alcohol in the presence of the tetrazene radical salt type alcohol oxidation catalyst according to claim 5 and a co-oxidant.

11. The method for oxidizing an alcohol according to claim 10, wherein the alcohol is a primary alcohol or a secondary alcohol.

12. The method for oxidizing alcohol according to claim 10 or 11, wherein the amount of the tetrazene radical salt type alcohol oxidation catalyst added is 0.01 mole or more and 100 moles or less per 100 moles of all hydroxy groups in the alcohol.

13. A method for oxidizing an alcohol, which comprises oxidizing an alcohol in the presence of the tetrazene-type alcohol oxidation catalyst according to claim 6 and a co-oxidant.

14. The method for oxidizing an alcohol according to claim 13, wherein the alcohol is a primary alcohol or a secondary alcohol.

15. The method for oxidizing an alcohol according to claim 13 or 14, wherein the amount of the tetrazene-type alcohol oxidation catalyst added is 0.01 moles or more and 100 moles or less per 100 moles of all hydroxy groups in the alcohol.

Images