Production method for monoorganophosphine having tertiary alkyl group

Abstract

Provided is a method for producing a monoorganophosphine having a tertiary alkyl group via an industrially advantageous method. This production method for a monoorganophosphine having a tertiary alkyl group comprises a reaction step for reacting a phosphine and a specific ester compound in a solvent in the presence of a trialkylsilyl triflate, wherein the added quantity of the phosphine is 1.5 times the moles or more relative to the trialkylsilyl triflate, and the added quantity of the ester compound is 1.5 times the moles or more relative to the phosphine.

Description

Method for producing monoorganophosphines having tertiary alkyl groups

[0001] The present invention relates to a method for producing monoorganophosphines having a tertiary alkyl group.

[0002] Monoorganophosphines are used as flame retardants and antistatic agents for fibers, plastics, etc., and also as phosphorus raw materials for metalorganic chemical vapor deposition processes such as epitaxial growth processes.

[0003] Because monoorganophosphines have two highly reactive active hydrogen atoms, they can be added to compounds having unsaturated bonds and, in some cases, oxidized to produce a variety of useful compounds. For example, by adding allyl alcohol or acrylic acid, bifunctional compounds useful as flame retardants can be easily obtained. Furthermore, by adding an unsaturated alkyl group, phosphines with different alkyl chain lengths can be obtained, and further, phosphine oxides and phosphonium salts can be obtained. Furthermore, by oxidizing monoorganophosphines, phosphinic acids and phosphonic acids can be sequentially obtained, thereby producing a variety of useful functional compounds.

[0004] As a method for producing monoorganophosphines, a method has been proposed in which a phosphine is reacted with an alkyl halide in an aqueous alkaline solution and an organic solvent in the presence of a catalyst (for example, Patent Documents 1 and 2).

[0005] Furthermore, catalysts using phosphine ligands having an asymmetric center on the phosphorus atom are known to be useful as catalysts for asymmetric hydrogenation reactions and coupling reactions. The stereocontrol effect of a substituent near the catalytic reaction site tends to be enhanced when the substituent is bulky. For this reason, those having a bulky tertiary alkyl group such as a tert-butyl group or an adamantyl group are often used for such applications, and monoorganophosphines having a tertiary alkyl group are useful as raw materials for synthesizing such phosphine ligands (e.g., Patent Document 3).

[0006] However, with the methods of Patent Documents 1 and 2, it is difficult to obtain a monoorganophosphine having a tertiary alkyl group itself.

[0007] As a method for synthesizing a monoorganophosphine having a tertiary alkyl group, for example, a method has been proposed in which a phosphine and an alkene are reacted using one or a mixture of two or more kinds of alkane sulfonic acid anhydrides as a catalyst (for example, Patent Document 4, etc.). However, although this method is effective for producing limited monoorganophosphines such as tert-butylphosphine, the compounds that can be produced are limited because an alkene is used as a raw material, and it is not possible to produce, for example, 1-adamantylphosphine as a monoorganophosphine having a tertiary alkyl group.

[0008] Furthermore, Non-Patent Document 1 proposes a method for producing a diorganophosphine having a tertiary alkyl group from a phosphine, an ester compound, and a trialkylsilyl triflate. According to Non-Patent Document 1, for example, in the synthesis of di-1-adamantylphosphine, the reaction is carried out at a molar ratio of phosphine:ester compound:trialkylsilyl triflate=1:1:3.

[0009] Japanese Patent Application Laid-Open No. 2002-255983 Japanese Patent Application Laid-Open No. 2001-354683 Japanese Patent Application Laid-Open No. 2001-253889 Japanese Patent Application Laid-Open No. 06-271592

[0010] ACS Catal. ,2022,12,5123-5135

[0011] However, when the reaction is carried out according to the method disclosed in Non-Patent Document 1, even when a phosphine and an ester compound are reacted in a 1:1 ratio, only a salt of a diorganophosphine is produced, and the production of a monoorganophosphine cannot be confirmed.

[0012] That is, an object of the present invention is to provide a method for producing a monoorganophosphine having a tertiary alkyl group in an industrially advantageous manner.

[0013] The present inventors, while investigating a method for producing a monoorganophosphine having a tertiary alkyl group using phosphine as a phosphorus source, found that in a method in which a phosphine is reacted with an ester compound having a specific tertiary alkyl group in a solvent in the presence of a trialkylsilyl triflate, by adjusting the addition ratio of each raw material to fall within a specific range, a monoorganophosphine is produced specifically together with a diorganophosphonium salt, and that the monoorganophosphine and the diorganophosphonium salt can be easily separated, thereby completing the present invention.

[0014] The present invention provides a method for producing a monoorganophosphine having a tertiary alkyl group represented by the following general formula (2), which comprises a reaction step of reacting a phosphine with an ester compound represented by the following general formula (1) in a solvent in the presence of a trialkylsilyl triflate, wherein the amount of the phosphine added is 1.5 times or more by mole relative to the trialkylsilyl triflate, and the amount of the ester compound added is 1.5 times or more by mole relative to the phosphine:

[0015] (In the formula, R represents a branched or cyclic tertiary alkyl group, and the alkyl group may be substituted with a group selected from an alkyl group, an aryl group, a halogen group, a hydroxyl group, an alkoxy group, an amino group, and a substituted amino group; and n represents an integer of 0 to 1.)

[0016] (In the formula, R has the same meaning as R in general formula (1).)

[0017] According to the present invention, a monoorganophosphine having a tertiary alkyl group can be produced by an industrially advantageous method.

[0018] The present invention will be described below based on preferred embodiments. The monoorganophosphine obtained by the production method of the present invention is a compound represented by the following general formula (2).

[0019] (In the formula, R represents a branched or cyclic tertiary alkyl group, and the alkyl group may be substituted with a group selected from an alkyl group, an aryl group, a halogen group, a hydroxyl group, an alkoxy group, an amino group, and a substituted amino group.)

[0020] The branched or cyclic tertiary alkyl group represented by R in general formula (2) is a group represented by the following general formula (4).

[0021] (In the formula, R １ , R ２ and R ３ represents an alkyl group having 1 to 20 carbon atoms or a cycloalkyl group having 3 to 30 carbon atoms. １ , R ２ and R ３ may be bonded to each other to form a ring structure or a bridged polycyclic structure.

[0022] The alkyl group having 1 to 20 carbon atoms may be linear or branched. Examples of linear alkyl groups include methyl, ethyl, propyl, butyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, and octadecyl. Examples of branched alkyl groups include isopropyl, sec-butyl, tert-butyl, isobutyl, isopentyl, tert-pentyl, 2-hexyl, 3-hexyl, 2-heptyl, 3-heptyl, isoheptyl, tert-heptyl, isooctyl, tert-octyl, 2-ethylhexyl, and isononyl.

[0023] Examples of the cycloalkyl group having 3 to 30 carbon atoms include saturated monocyclic alkyl groups having 3 to 30 carbon atoms, saturated polycyclic alkyl groups having 3 to 30 carbon atoms, and groups having 4 to 30 carbon atoms in which hydrogen atoms in these groups are substituted with alkyl groups. Examples of the saturated monocyclic alkyl group include monocyclic cycloalkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, and cyclodecyl; and polycyclic cycloalkyl groups such as adamantyl, decahydronaphthyl, octahydropentalene, and bicyclo[1.1.1]pentanyl.

[0024] The R １ , R ２ and R ３ When these are bonded to each other to form a ring structure, examples of the group include the above-mentioned cycloalkyl groups having 3 to 30 carbon atoms.

[0025] The branched or cyclic tertiary alkyl group represented by R may have a substituent. Examples of the substituent include an alkyl group, an aryl group, a halogen group, a hydroxyl group, an alkoxy group, an amino group, and a substituted amino group.

[0026] The alkyl group may be linear or branched, and examples thereof include alkyl groups having 1 to 6 carbon atoms. The aryl group includes aryl groups having 6 to 14 carbon atoms. Specific examples include phenyl, naphthyl, and anthryl groups. The substituted amino group includes amino groups in which at least one hydrogen atom of the amino group is substituted with a substituent such as an alkyl group, a cycloalkyl group, a halogenated alkyl group, an alkoxy group, or a halogen atom.

[0027] Preferable examples of the branched tertiary alkyl group represented by R in general formula (2) include a tert-butyl group, a tert-pentyl group, a tert-amyl group, a 3-methyl-3-pentyl group, a 3-ethyl-3-pentyl group, a 2,3-dimethyl-2-butyl group, a 2,3,3-trimethyl-2-butyl group, and a 2-methyl-4-phenyl-2-butyl group.

[0028] Preferable examples of the cyclic tertiary alkyl group represented by R in general formula (2) include a 1-methylcyclopentyl group, a 1-methylcyclohexyl group, a 1-phenylcyclohexyl group, a 1-adamantyl group, and a 2-methyl-2-adamantyl group.

[0029] In the present invention, R in general formula (2) is preferably a tert-butyl group, a tert-pentyl group, a 2-methyl-2-pentyl group, a 3-methyl-3-pentyl group, a tert-hexyl group, a 1,2-dimethylcyclobutyl group, a 1-methylcyclopentyl group, or a 1-adamantyl group, and particularly preferably a 1-adamantyl group.

[0030] The method for producing a monoorganophosphine of the present invention includes a reaction step of reacting a phosphine with an ester compound represented by the following general formula (1) in a solvent in the presence of a trialkylsilyl triflate (trialkylsilyl trifluoromethanesulfonate):

[0031] (In the formula, R has the same meaning as R in general formula (2), and n represents an integer of 0 to 1.)

[0032] In the present invention, n in general formula (1) is preferably 0. R in general formula (1) is as described above.

[0033] The ester compound represented by general formula (1) can be produced by a known method, for example, by reacting an alcohol with acetic anhydride or propionic anhydride in pyridine in the presence of 4-dimethylaminopyridine according to the following reaction scheme (1) (see, for example, ACS Catal., 2022, 12, 5123-5135).

[0034] (R and n in the formula have the same meanings as R and n in general formula (1).)

[0035] Examples of the trialkylsilyl triflate used in the production method of the present invention include trimethylsilyl triflate, triethylsilyl triflate, tert-butyldimethoxysilyl triflate, and dimethylvinylsilyl triflate, with trimethylsilyl triflate being particularly preferred.

[0036] Examples of the solvent used in the production method of the present invention include aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as hexane, octane, and paraffin; and halogenated hydrocarbons such as dichloromethane, chloroform, carbon tetrachloride, ethyl chloride, dichloroethane, trichloroethane, tetrachloroethane, pentachloroethane, hexachloroethane, dichloroethylene, trichloroethylene, tetrachloroethylene, propyl chloride, dichloropropane, trichloropropane, butyl chloride, chloropentane, chlorobenzene, chlorotoluene, and dichlorobenzene.

[0037] In the production method of the present invention, the amount of phosphine added is 1.5 times or more by mole relative to the trialkylsilyl triflate. The reason for this is that if the amount of phosphine added is less than 1.5 times by mole relative to the phosphine, the monoorganophosphine having a tertiary alkyl group itself will not be produced at all. Furthermore, from the viewpoint of obtaining the target monoorganophosphine having a tertiary alkyl group in good yield, the amount of phosphine added is preferably 2 times or more by mole relative to the trialkylsilyl triflate, more preferably 2 to 4 times by mole, and particularly preferably 2 to 3 times by mole.

[0038] In the production method of the present invention, the amount of the ester compound added is 1.5 times or more by mole relative to the phosphine. The reason for this is that if the amount of the ester compound added is less than 1.5 times by mole relative to the phosphine, no monoorganophosphine having a tertiary alkyl group will be produced at all. Furthermore, from the viewpoint of obtaining the target monoorganophosphine having a tertiary alkyl group in good yield, the amount of the ester compound added as a raw material is preferably 2 times or more by mole relative to the phosphine, more preferably 2 to 4 times by mole, and particularly preferably 2 to 3 times by mole.

[0039] In the production method of the present invention, it is preferable to charge the ester compound represented by the general formula (1), trialkylsilyl triflate, and a solvent into a reaction vessel, and then introduce phosphine gas to carry out the reaction.

[0040] The reaction temperature varies depending on the type of ester compound represented by general formula (1), but in many cases it is preferably 10° C. or higher, more preferably 30 to 80° C. If the reaction temperature is lower than 10° C., the reaction tends to proceed slowly, and the yield of the target product, monoorganophosphine having a tertiary alkyl group, decreases, which is undesirable.

[0041] The reaction pressure is not particularly limited, and the reaction can be carried out under reduced pressure, atmospheric pressure, or increased pressure. It is preferable to keep the reaction vessel under an inert gas atmosphere from the viewpoint of preventing ignition of phosphine gas. The reaction time is usually 1 hour or more, preferably 4 hours or more, and more preferably 4 to 10 hours.

[0042] When the reaction is carried out using phosphine gas, the internal pressure of the reaction system may become high if the entire amount is injected into the reaction system. Therefore, the phosphine gas may be injected in several portions while the reaction is proceeding.

[0043] The reaction solution after completion of the reaction contains a monoorganophosphine having a tertiary alkyl group represented by the general formula (2) above and a diorganophosphonium salt represented by the following general formula (3).

[0044] (In the formula, R has the same meaning as R in general formula (1).)

[0045] That is, the production method of the present invention can simultaneously produce the monoorganophosphine having a tertiary alkyl group represented by the general formula (2) and the diorganophosphonium salt represented by the general formula (3).

[0046] The diorganophosphonium salt represented by general formula (3) can be easily separated from the reaction solution after completion of the reaction by the following separation step: The reaction solution containing the monoorganophosphine having a tertiary alkyl group represented by general formula (2) obtained in the reaction step and the diorganophosphonium salt represented by general formula (3) is concentrated under reduced pressure, and then an organic solvent that dissolves the monoorganophosphine having a tertiary alkyl group represented by general formula (2) but does not or hardly dissolves the diorganophosphonium salt represented by general formula (3) is added, and solid-liquid separation is carried out by a conventional method such as filtration, whereby the diorganophosphonium salt can be separated as crystals.

[0047] Examples of organic solvents that can be used in the separation step include tetrahydrofuran, N,N-dimethylformamide, diethyl ether, tert-butyl methyl ether, cyclopentyl methyl ether, dioxane, hexane, and toluene. These solvents can be used alone or as a mixed solvent.

[0048] The reaction solution obtained after separating the diorganophosphonium salt represented by general formula (3) in the separation step contains a monoorganophosphine having a tertiary alkyl group represented by general formula (2). The reaction solution may contain the starting ester compound represented by general formula (1), but the monoorganophosphine having a tertiary alkyl group can be easily isolated by fractionating the reaction solution or by hydrolyzing the ester compound represented by general formula (1) using a strong alkaline aqueous solution such as potassium hydroxide.

[0049] The monoorganophosphine having a tertiary alkyl group represented by general formula (2) obtained by the production method of the present invention can be used, for example, as a flame retardant for fibers, plastics, etc., an antistatic agent, a phosphorus source used in organometallic chemical vapor deposition methods such as epitaxial growth methods, a phosphorus source for phosphine ligands, etc.

[0050] Furthermore, the diorganophosphonium salt represented by the general formula (3) can be converted into a diorganophosphine by treating it with an alkali, and can be used as a phosphorus source for a phosphine ligand.

[0051] Although the present inventors are not certain about the reaction mechanism, they speculate that the diorganophosphonium salt represented by general formula (3) is produced first, and then the monoorganophosphine having a tertiary alkyl group represented by general formula (2) is produced in greater amount, and therefore the diorganophosphonium salt represented by general formula (3) produced first acts as a catalyst to produce the monoorganophosphine having a tertiary alkyl group represented by general formula (2).

[0052] The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0053] [Production Example] <Preparation of 1-adamantyl acetate> 1-Adamantanol (213 g, 1.40 mol), DMAP (17.1 g, 0.14 mol), pyridine (274 g, 3.46 mol), and acetic anhydride (214 g, 2.10 mol) were charged into a 1000 mL glass flask equipped with a stirrer, and the mixture was heated with stirring to raise the temperature to 70°C. After stirring at 70°C for 8 hours, the reaction solution was transferred to a 2000 mL separatory funnel, and toluene (555 g) and water (530 g) were added, followed by removal of the lower aqueous layer. The organic layer was washed with water (656 g), hydrochloric acid (4%, 638 g, 0.70 mol), aqueous sodium bicarbonate solution (6%, 979 g, 0.70 mol) twice, and then with water (656 g), and then concentrated to 272 g. Quantitative analysis by gas chromatography revealed that the 1-adamantyl acetate content was 93% and the yield was 93%. The product was further purified by distillation to increase its purity and used in the next reaction.

[0054]

[0055] (Identification data for 1-adamantyl acetate) １ H NMR (500MHz, CDCl ３ ): δ 2.17-2.14 (m, 3H), 2.11-2.09 (m, 6H), 1.96 (s, 3H), 1.70-1.62 (m, 6H) １３ C{ １ H} NMR (126MHz, CDCl ３): δ 170.2, 80.2, 41.3, 36.2, 30.8, 22.7

[0056] Example 1 Synthesis of 1-adamantylphosphine (Reaction Step) 1-adamantyl acetate (233 g, 1.20 mol: AdOAc), trimethylsilyl trifluoromethanesulfonate (44.5 g, 0.20 mol: TMSOTF), and dichloromethane (690 g) were placed in a 1000 mL Hastelloy-B autoclave equipped with a stirrer, and stirring was initiated. After the interior was purged with nitrogen, the pressure was reduced, and phosphine (20.4 g, 0.60 mol) was introduced at 15°C. After the phosphine introduction, the temperature was raised to 50°C, and stirring was continued for 4 hours. After cooling to room temperature, the remaining phosphine was removed by nitrogen substitution. The reaction solution was then ３１ P NMR analysis showed peaks for di-1-adamantylphosphonium triflate (3a) and 1-adamantylphosphine (2a), with almost no other peaks observed. ３１ The crystallinity was determined by P NMR, and the results are shown in Table 1. (Separation Step) This reaction solution was concentrated under reduced pressure to 300 g. 300 g of tert-butyl methyl ether was added, and purified crystals were separated by filtration, and the filtrate was concentrated. The separated crystals were almost pure di-1-adamantylphosphonium triflate. The filtrate after concentration was a mixture of 1-adamantylphosphine and 1-adamantyl acetate. The concentrated filtrate was purified by fractional distillation to obtain 20.0 g (yield 59.4%) of 1-adamantylphosphine.

[0057]

[0058] (Identification data for 1-adamantylphosphine (2a)) ３１ P NMR (162 MHz, CDCl ３ ): δ -82.1(t, １ J ＰＨ = 190.7 Hz) １ H NMR (500MHz, CDCl ３ ): δ 2.66 (d, １ J ＨＰ =192.7Hz, 2H, PH ２), 1.93 (br s, 3H, CH), 1.80-1.77 (m, 6H, CH ２ ), 1.73-1.63 (m, 6H, CH ２ ) １３ C{ １ H} NMR (126MHz, CDCl ３ ): δ 44.7(d, ２ J ＣＰ = 8.2 Hz, CH ２ ), 36.3(s, CH ２ ), 28.9 (d, ３ J ＣＰ =7.7Hz,CH)

[0059] [Example 2] The reaction was carried out in the same manner as in Example 1, except that the raw materials trimethylsilyl trifluoromethanesulfonate (TMSOTF), phosphine, and 1-adamantyl acetate (AdOAc) were charged as shown in Table 1. The product ratio (2a / 3a) in the reaction solution was ３１ The results are shown in Table 1.

[0060] Comparative Example 1 (Reaction Step) 1-adamantyl acetate (79.5 g, 0.41 mol; AdOAc), trimethylsilyl trifluoromethanesulfonate (90.9 g, 0.41 mol; TMSOTF), and dichloromethane (706 g) were charged into a 1000 mL Hastelloy-B autoclave equipped with a stirrer, and stirring was initiated. After the interior was purged with nitrogen, the pressure was reduced, and phosphine (13.9 g, 0.41 mol) was introduced at 15°C. After the phosphine was introduced, the temperature was raised to 50°C, and stirring was continued for 4 hours. After cooling to room temperature, the remaining phosphine was removed by nitrogen substitution. Here, the reaction solution ３１ P NMR analysis showed that diadamantylphosphonium triflate (3a) and a small amount of unspecified peaks were observed, but no peak for adamantylphosphine (2a) was observed. The product ratio (2a / 3a) in the reaction mixture was ３１The crystallinity was determined by PNMR, and the results are shown in Table 1. (Removal Step) This reaction solution was concentrated, and tert-butyl methyl ether was added thereto, and the crystals were filtered off, whereby di-1-adamantylphosphonium triflate could be obtained, but 1-adamantylphosphine could not be obtained.

[0061] Comparative Examples 2 to 4 Reactions were carried out in the same manner as in Comparative Example 1, except that the raw materials trimethylsilyl trifluoromethanesulfonate (TMSOTF), phosphine, and 1-adamantyl acetate (AdOAc) were charged as shown in Table 1. The product ratio (2a / 3a) in the reaction solution was ３１ The results are shown in Table 1.

[0062]

[0063] The results in Table 1 show that the production method of the present invention can produce monoorganophosphines having a tertiary alkyl group and can also produce diorganophosphonium salts.

Claims

1. A method for producing a monoorganophosphine having a tertiary alkyl group represented by the following general formula (2), comprising a reaction step of reacting a phosphine with an ester compound represented by the following general formula (1) in a solvent in the presence of trialkylsilyl triflate, wherein the amount of the phosphine added is 1.5 times or more by mole relative to the trialkylsilyl triflate, and the amount of the ester compound added is 1.5 times or more by mole relative to the phosphine. (In the formula, R represents a branched or cyclic tertiary alkyl group, and the alkyl group may be substituted with a group selected from an alkyl group, an aryl group, a halogen group, a hydroxyl group, an alkoxy group, an amino group, and a substituted amino group; and n represents an integer of 0 to 1.) (In the formula, R has the same meaning as R in general formula (1).) 2. A method for producing a monoorganophosphine having a tertiary alkyl group according to claim 1, wherein R in the general formula (1) is a 1-adamantyl group.

3. The method for producing a monoorganophosphine having a tertiary alkyl group according to claim 1, wherein the trialkylsilyl triflate is trimethylsilyl triflate.

4. The method for producing a monoorganophosphine having a tertiary alkyl group according to claim 1, wherein the amount of the phosphine added is 2.0 times or more by mole relative to the trialkylsilyl triflate, and the amount of the ester compound added is 2.0 times or more by mole relative to the phosphine.

5. A method for producing a monoorganophosphine having a tertiary alkyl group according to claim 1, which also produces a diorganophosphonium salt represented by the following general formula (3): (In the formula, R has the same meaning as R in general formula (1).) 6. A method for producing a monoorganophosphine having a tertiary alkyl group according to claim 1, comprising a separation step of adding an organic solvent to a concentrate obtained by concentrating the reaction solution obtained in the reaction step, and isolating the diorganophosphonium salt represented by the following general formula (3) as crystals from the organic solvent: (In the formula, R has the same meaning as R in general formula (1).)

Images