Palladium complex, coupling reaction catalyst, and method for producing aromatic compounds

Abstract

The present invention provides a palladium complex which enables a coupling reaction to progress in a short period of time even under mild reaction conditions such as at room temperature, and which enables the achievement of a target product with high yield; and the present invention uses a palladium complex which is represented by general formula (A). (In the formula, X represents a chlorine atom or the like; each of R1 to R3 independently represents an alkyl group having from 1 to 6 carbon atoms, said alkyl group being optionally substituted by a fluorine atom, or the like; and each of R4 to R6 independently represents an alkyl group having from 1 to 20 carbon atoms, or the like.)

Description

REFERENCE TO RELATED APPLICATIONS

[0001] This patent application claims priority to Japanese Patent Application No. 2020-196287, filed on November 26, 2020, the entire disclosure of which is incorporated herein by reference. [Technical Field]

[0002] The present invention relates to a novel palladium complex that can be used as a catalyst for coupling reactions, and more particularly to a palladium complex that can be suitably used as a catalyst for cross-coupling reactions such as the Suzuki-Miyaura reaction. [Background technology]

[0003] Chemical reactions that create carbon-carbon bonds are extremely important in the field of organic synthesis, including pharmaceutical synthesis. Grignard reagents, which involve attaching a metal atom with low electronegativity to a carbon atom to polarize the carbon atom and use it as a nucleophilic reagent, have long been used to create carbon-carbon bonds. However, Grignard reagents have problems such as carcinogenicity, a high boiling point, which makes them difficult to handle, and their high reactivity means they cannot be handled in the presence of water, requiring extreme care during chemical synthesis.

[0004] Therefore, in recent years, the Suzuki-Miyaura coupling reaction, which forms a carbon-carbon bond between an organoboron compound and an aryl halide, has attracted attention. For example, Patent Document 1 discloses that a carbon-carbon bond was formed by performing a wet Suzuki-Miyaura coupling reaction between an aromatic boronic acid ester and an aromatic compound other than the aromatic boronic acid ester in the presence of a solid catalyst containing palladium.

[0005] Patent Document 2 discloses the use of a palladium complex containing di-tert-butyl(3-methyl-2-butenyl)phosphine as a palladium ligand as a Suzuki-Miyaura coupling catalyst. Patent Document 3 discloses the use of a palladium complex containing chloromethyl(tri-tert-butylphosphine) or the like as a palladium ligand as a Suzuki-Miyaura coupling catalyst. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-31190 [Patent Document 2] International Publication No. 2014-115813 [Patent Document 3] International Publication No. 2017-094655 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in order to carry out a coupling reaction using the palladium complex or the like described in Patent Document 2, a reaction temperature of nearly 100°C is required. Therefore, when producing unstable pharmaceutical and agrochemical intermediates or organic electronic materials, high temperatures can cause problems such as decomposition of the target product or generation of unintended by-products. In view of the above problems, an object of the present invention is to provide a palladium complex that allows a coupling reaction to proceed in a short time and gives a target product in high yield even under mild reaction conditions such as room temperature. [Means for solving the problem]

[0008] As a result of extensive research, the present inventors have discovered a palladium complex that can be used as a coupling reaction catalyst, which allows a coupling reaction to proceed in a short time and gives a target product in high yield even under mild reaction conditions by using a ligand coordinated to palladium with a specific structure, and have completed the present invention.

[0009] [1] A palladium complex represented by the following general formula (A): [ka] (In the formula, X represents a chlorine atom, a bromine atom, or an iodine atom; R 1 ~R 3 each independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms which may be substituted with a fluorine atom, an aryl group having 6 to 20 carbon atoms which may have a substituent, or a heteroaryl group having 4 to 20 carbon atoms which may have a substituent; R 4 ~R 6 each independently represents a hydrogen atom, a fluorine atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms which may have a substituent, or a heteroaryl group having 4 to 20 carbon atoms which may have a substituent, Substituents which the aryl group and heteroaryl group may have are at least one group selected from the group consisting of a fluorine atom, an alkyl group, a cycloalkyl group, an alkoxy group, a cycloalkoxy group, an alkylthio group, a cycloalkylthio group, an aryl group, an aryloxy group, an arylthio group, an arylalkyl group, an arylcycloalkyl group, an arylalkenyl group, an arylalkynyl group, a heterocyclic group which may have an alkyl group, a group represented by -N(R')2 (wherein the two R's each independently represent a hydrogen atom, a hydrocarbon group having 1 to 10 carbon atoms, or a heterocyclic group which may have an alkyl group), a group represented by -Si(R')3 (wherein R' is as defined above, and the three R's may be the same or different), an acyl group, a group having a carbon-nitrogen double bond, an acid imide group, an alkoxycarbonyl group, a cycloalkoxycarbonyl group, an aryloxycarbonyl group, a carboxy group, a cyano group, a nitrile group, and a nitro group; R 4 ~R 6 All three of the above represent phenyl groups, and R 4 ~R 6 Two of these cannot be methyl groups and the remaining one cannot be a phenyl group.) [2] R in the general formula (A) 1 and R 2 is a methyl group, and R 3 is a hydrogen atom. [3] The palladium complex according to [1] or [2], wherein X in the general formula (A) is a chlorine atom. [4] R in the general formula (A) 4 ~R 6 The palladium complex according to any one of [1] to [3], wherein at least one of the following is a tert-butyl group: [5] R in the general formula (A) 4 ~R 6 The palladium complex according to any one of [1] to [4], wherein at least one of the above is a substituted aryl group, an alkenyl group having 2 to 6 carbon atoms, or a cycloalkyl group having 5 to 8 carbon atoms. [6] The palladium complex according to any one of [1] to [5], which is represented by the following formula (A1) or (A2): [ka] [7] A coupling reaction catalyst comprising the palladium complex according to any one of [1] to [6]. [8] A method for producing a palladium complex represented by general formula (A), comprising: A step of reacting a bis(β-diketonato)palladium complex with a phosphine compound represented by the following general formula (a) to obtain a reaction intermediate; reacting the reaction intermediate with hydrogen chloride, hydrogen bromide, or hydrogen iodide to obtain the palladium complex; A method for producing a palladium complex, comprising: [ka] (In the formula, R 4 ~R 6 has the same definition as above.) [9] A method for producing an aromatic compound, comprising: subjecting an aromatic boronic acid compound (B) or an aromatic boronic acid ester (B') to a coupling reaction with an aromatic compound (C) in the presence of the palladium complex according to any one of [1] to [6] to produce a carbon-carbon coupling reaction product (D).

[10] The method according to [9], wherein the reaction temperature of the coupling reaction is 40°C or lower. [Effects of the Invention]

[0010] The palladium complex of the present invention can be used as a catalyst for coupling reactions to produce reaction products with high productivity even under mild conditions. In particular, when the palladium complex of the present invention is applied to the reaction of an aromatic compound having a halogen atom with a boron compound (Suzuki-Miyaura coupling), the target product can be produced in high yield under extremely mild conditions of room temperature and atmospheric pressure. For these reasons, the palladium complex of the present invention is useful for the production of information and electronic materials and pharmaceutical and agrochemical intermediates, and can be said to be extremely valuable industrially. DETAILED DESCRIPTION OF THE INVENTION

[0011] An example of a preferred embodiment of the present invention will be described below. However, the following embodiment is an example for explaining the present invention, and the present invention is not limited to the following embodiment.

[0012] [Palladium complexes] The palladium complex according to the present invention is represented by the following general formula (A). [ka]

[0013] In the general formula (A), X represents a chlorine atom, a bromine atom, or an iodine atom, and among these, a chlorine atom is preferred for X from the viewpoint of reactivity at low temperatures.

[0014] In the above general formula (A), R 1 ~R 3 each independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms which may be substituted with a fluorine atom, an aryl group having 6 to 20 carbon atoms which may have a substituent, or a heteroaryl group having 4 to 20 carbon atoms which may have a substituent.

[0015] The alkyl group may be linear or branched. Examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, a 2,2-dimethylpropyl group, an n-hexyl group, and a 2-methylpentyl group.

[0016] The alkyl group which may be substituted with a fluorine atom is an alkyl group which may have a fluorine atom as a substituent. The alkyl group has the same meaning as defined above.

[0017] Among the above-mentioned alkyl groups, from the viewpoints of reactivity at low temperatures and the stability of the complex structure, a methyl group, a difluoromethyl group, a trifluoromethyl group, an ethyl group, an isopropyl group, a perfluoropropyl group, a tert-butyl group, or a pentyl group is preferred, a methyl group, a difluoromethyl group, a trifluoromethyl group, an ethyl group, an isopropyl group, a perfluoropropyl group, or a tert-butyl group is more preferred, and a methyl group is even more preferred.

[0018] An aryl group is a group generated by removing one hydrogen atom bonded to an aromatic hydrocarbon ring. Examples of aryl groups having 6 to 20 carbon atoms include a phenyl group, a 4-methylphenyl group, a 2-methylphenyl group, a 2,6-dimethylphenyl group, a 1-naphthyl group, a 2-naphthyl group, a 3-phenanthryl group, and a 2-anthryl group. Examples of the aryl group having 6 to 20 carbon atoms which may have a substituent include a phenyl group, a 2-methylphenyl group, a 3-methylphenyl group, a 4-methylphenyl group, a 2,3-dimethylphenyl group, a 2,4-dimethylphenyl group, a 2,5-dimethylphenyl group, a 2,6-dimethylphenyl group, a 3,5-dimethylphenyl group, a 2,4,6-trimethylphenyl group, a 2,3,5,6-tetramethylphenyl group, a 2-ethylphenyl group, a 3,5-diethylphenyl group, a 4-n-propylphenyl group, a 4-isopropylphenyl group, a 4-n-butylphenyl group, a 4-tert-butylphenyl group, a 1-naphthyl group, a 2-naphthyl group, a 2-biphenyl group, a 3-biphenyl group, a 4-biphenyl group, a 2-fluoro-4-biphenyl group, a 2-fluorenyl group, a 9-phenanthrenyl group, a 9-anthracenyl group, a 1-pyrenyl group, a 2-trifluoromethylphenyl group, a 3-methylphenyl group, a 2 ... -trifluoromethylphenyl group, 4-trifluoromethylphenyl group, 3,5-bis(trifluoromethyl)phenyl group, 2-methoxyphenyl group, 3-methoxyphenyl group, 4-methoxyphenyl group, 2,4-dimethoxyphenyl group, 2,5-dimethoxyphenyl group, 2,6-dimethoxyphenyl group, 3,4-dimethoxyphenyl group, 3,5-dimethoxyphenyl group, 2-ethoxyphenyl group, 3-ethoxyphenyl group, 4-ethoxyphenyl group, 2-(benzyloxy)phenyl group, 2-phenoxyphenyl group, 4-phenoxyphenyl group, 2,3-methylenedioxyphenyl group, 3,4-methylenedioxyphenyl group, 2-fluorophenyl group, 3-fluorophenyl group, 4-fluorophenyl group, 2,4-difluorophenyl group, 2,5-difluorophenyl group, 2,6-difluorophenyl group, 3,4-difluorophenyl group, 3,Examples of such phenyl groups include 5-difluorophenyl, 2-formylphenyl, 3-formylphenyl, 4-formylphenyl, 3-formyl-4-methoxyphenyl, 2-cyanophenyl, 3-cyanophenyl, 4-cyanophenyl, 2-acetylphenyl, 3-acetylphenyl, 4-acetylphenyl, 3-carboxyphenyl, 3-aminophenyl, 2-(N,N-dimethylamino)phenyl, 3-(N,N-dimethylamino)phenyl, 4-(N,N-dimethylamino)phenyl, and 2-(N,N-dimethylaminomethyl)phenyl.

[0019] A heteroaryl group is a group in which a carbon atom constituting the ring of an aryl group is substituted with a heteroatom or a carbonyl group. Heteroaryl groups having 4 to 20 carbon atoms include monocyclic heteroaryl groups, fused-ring heteroaryl groups, monovalent groups formed by two or more monocyclic and / or fused-ring heteroaryl groups bonded directly or indirectly via a heteroatom (such as an oxygen atom, nitrogen atom, or sulfur atom) or a carbonyl group (-CO-), and monovalent groups formed by one or more monocyclic and / or fused-ring heteroaryl groups bonded indirectly to one or more monocyclic and / or fused-ring aryl groups directly or via a heteroatom (such as an oxygen atom, nitrogen atom, or sulfur atom) or a carbonyl group (-CO-). The remaining bond of the nitrogen atom that indirectly bonds the heteroaryl group is bonded to, for example, an optionally substituted alkyl group or an optionally substituted aryl group. The fused ring contained in the fused ring heteroaryl group may be a fused ring of two or more hetero rings, or a fused ring of one or more hetero rings and one or more aromatic rings.

[0020] Examples of the heteroaryl group having 4 to 20 carbon atoms include groups represented by general formulae (ha1) to (ha7).

[0021] [ka] (In the formula, R represents a fluorine atom, an alkyl group, a cycloalkyl group, an alkoxy group, a cycloalkoxy group, an alkylthio group, a cycloalkylthio group, an aryl group, an aryloxy group, an arylthio group, an arylalkyl group, an arylcycloalkyl group, an arylalkenyl group, an arylalkynyl group, a heterocyclic group which may have an alkyl group, a group represented by -N(R')2 (two R's each independently represent a hydrogen atom, a hydrocarbon group having 1 to 10 carbon atoms, or a heterocyclic group which may have an alkyl group), a group represented by -Si(R')3 (R' is as defined above, and the three R's may be the same or different), an acyl group, a group having a carbon-nitrogen double bond, an acid imide group, an alkoxycarbonyl group, a cycloalkoxycarbonyl group, an aryloxycarbonyl group, a carboxy group, a cyano group, a nitrile group, or a nitro group. Furthermore, p represents an integer of 0 to 4. Y is a sulfur atom, an oxygen atom, or -NR Y represents a group represented by the formula: Also, R Y represents a hydrogen atom, an alkyl group which may have a substituent, or an aryl group which may have a substituent. Furthermore, ring A represents a heterocycle or an aromatic ring.

[0022] Examples of the groups represented by the above general formulae (ha1) to (ha4) include groups represented by the following general formulae (ha1-1) to (ha4-12). [ka] (In the formula, R and p have the same meanings as defined above.)

[0023] [ka] (In the formula, R and p have the same meanings as defined above.)

[0024] Among the above-mentioned heteroaryl groups having 4 to 20 carbon atoms which may have a substituent, a 2-thienyl group, a 3-methyl-2-thienyl group, a 4-methyl-2-thienyl group, a 5-methyl-2-thienyl group, a 3,4-dimethyl-2-thienyl group, a 3,5-dimethyl-2-thienyl group, a 4,5-dimethyl-2-thienyl group, a 3-thienyl group, a 2-methyl-3-thienyl group, a 4-methyl-3-thienyl group, a 5-methyl-3-thienyl group, a 2,4-dimethyl-3-thienyl group, a 2,5-dimethyl-3-thienyl group, a 4,5-dimethyl-3-thienyl group, a 2-pyrrolyl group, a 1-methyl-2-pyrrolyl group, a 1-phenyl-2-pyrrolyl group, a 3-pyrrolyl group, a 1-methyl-3-pyrrolyl group, a 1-phenyl-3-pyrrolyl group, a 2-furyl group, Preferred are a 3-furyl group, a 2-pyridyl group, a 3-methyl-2-pyridyl group, a 4-methyl-2-pyridyl group, a 5-methyl-2-pyridyl group, a 6-methyl-2-pyridyl group, a 3-pyridyl group, a 2-methyl-3-pyridyl group, a 4-methyl-3-pyridyl group, a 5-methyl-3-pyridyl group, a 6-methyl-3-pyridyl group, a 3-pyridazinyl group, a 4-pyridazinyl group, a 2-pyrimidyl group, a 4-pyrimidyl group, a 5-pyrimidyl group, a 2-pyrazinyl group, a 2-triazinyl group, a 2-quinolyl group, an 8-quinolyl group, a 1-isoquinolyl group, a 3-isoquinolyl group, a 2-benzothienyl group, a 7-benzothionyl group, a 2-benzofuryl group, a 7-benzofuryl group, a 2-indolyl group, a 1-methyl-2-indolyl group, and a 1-phenylindolyl group.

[0025] In the above general formula, when R is an alkoxy group, the alkoxy group may be linear or branched. The number of carbon atoms in the alkoxy group is usually 1 to 20. Examples of the alkoxy group include a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, a sec-butoxy group, a tert-butoxy group, an n-pentyloxy group, a 2,2-dimethylpropoxy group, an n-hexyloxy group, an n-heptyloxy group, an n-octyloxy group, an n-nonyloxy group, an n-decyloxy group, an n-undecyloxy group, an n-dodecyloxy group, an n-tridecyloxy group, an n-tetradecyloxy group, an n-pentadecyloxy group, an n-hexadecyloxy group, an n-heptadecyloxy group, an n-octadecyloxy group, an n-nonadecyloxy group, and an n-icosyloxy group.

[0026] When R in the above general formula is a cycloalkoxy group, the number of carbon atoms in the cycloalkoxy group is usually 3 to 20. Examples of the cycloalkoxy group include a cyclopropoxy group, a cyclopentyloxy group, a cyclohexyloxy group, a cycloheptyloxy group, and a cyclooctyloxy group.

[0027] When R in the above general formula is an alkylthio group, the number of carbon atoms in the alkylthio group is usually 1 to 20. Examples of the alkylthio group include a methylthio group, an ethylthio group, an n-propylthio group, an isopropylthio group, an n-butylthio group, an isobutylthio group, a sec-butylthio group, a tert-butylthio group, an n-pentylthio group, an n-hexylthio group, an n-heptylthio group, an n-octylthio group, a 2-ethylhexylthio group, an n-nonylthio group, an n-decylthio group, a 3,7-dimethyloctylthio group, and an n-dodecylthio group.

[0028] When R in the above general formula is a cycloalkylthio group, the number of carbon atoms in the cycloalkylthio group is usually 3 to 20. Examples of the cycloalkylthio group include a cyclopropylthio group, a cyclopentylthio group, a cyclohexylthio group, a cycloheptylthio group, and a cyclooctylthio group.

[0029] When R in the above general formula is an aryloxy group, the number of carbon atoms in the aryl group is usually 6 to 20. Examples of the aryloxy group include a phenoxy group, a naphthyloxy group, a phenanthryloxy group, and an anthryloxy group. The aryloxy group is a group in which an aryl group is bonded to an oxy group.

[0030] When R in the above general formula is an arylthio group, the number of carbon atoms in the aryl group in the arylthio group is usually 6 to 20. Examples of the arylthio group include a phenylthio group and a naphthylthio group.

[0031] When R in the above general formula is an arylalkyl group, the number of carbon atoms in the aryl group is usually 6 to 20, and the number of carbon atoms in the alkyl group is usually 1 to 20. The arylalkyl group is an alkyl group having an aryl group as a substituent.

[0032] When R in the above general formula is an arylcycloalkyl group, the number of carbon atoms in the aryl group is usually 6 to 20, and the number of carbon atoms in the cycloalkyl group is usually 3 to 20. The arylcycloalkyl group is a cycloalkyl group having an aryl group as a substituent.

[0033] In the above general formula, when R is an arylalkenyl group, the number of carbon atoms in the aryl group is usually 6 to 20, and the number of carbon atoms in the alkenyl group is usually 2 to 8. Examples of arylalkenyl groups include phenylalkenyl groups and naphthylalkenyl groups. The arylalkenyl group is an alkenyl group having an aryl group as a substituent.

[0034] When R in the above general formula is an alkynyl group, the number of carbon atoms in the alkynyl group is usually 2 to 8. Examples of the alkynyl group include an ethynyl group, a 1-propynyl group, a 2-propynyl group, a 1-butynyl group, a 2-butynyl group, a 1-pentynyl group, a 2-pentynyl group, a 1-hexynyl group, a 2-hexynyl group, and a 1-octynyl group.

[0035] In the above general formula, when R is an arylalkynyl group, the number of carbon atoms in the aryl group is usually 6 to 20, and the number of carbon atoms in the alkynyl group is usually 2 to 8. Examples of arylalkynyl groups include phenylalkynyl groups and naphthylalkynyl groups. The arylalkynyl group is an alkynyl group having an aryl group as a substituent.

[0036] In the above general formula, when R is a heterocyclic group which may have an alkyl group as a substituent, the number of carbon atoms in the heterocyclic group is usually 3 to 20. Examples of heterocyclic groups include a thienyl group, a pyrrolyl group, a furyl group, a pyridyl group, a pyridazinyl group, a pyrimidyl group, a pyrazinyl group, a triazinyl group, a pyrrolidinyl group, a piperidinyl group, a quinolyl group, and an isoquinolyl group. Note that a heterocyclic group is an atomic group remaining after removing one hydrogen atom directly bonded to a carbon atom constituting the ring from a heterocyclic compound.

[0037] In the above general formula, when R is a group represented by -N(R')2, the two R's each independently represent a hydrogen atom, a hydrocarbon group having 1 to 10 carbon atoms, or a heterocyclic group which may have an alkyl group, and examples of the hydrocarbon group having 1 to 10 carbon atoms represented by R' include an alkyl group, a cycloalkyl group, and an aryl group. In the group represented by -N(R')2, it is preferable that at least one R' is a hydrocarbon group having 1 to 10 carbon atoms or a heterocyclic group which may have an alkyl group. Examples of groups represented by -N(R')2 include a methylamino group, a dimethylamino group, an ethylamino group, a diethylamino group, an n-propylamino group, a di-n-propylamino group, an isopropylamino group, a diisopropylamino group, an n-butylamino group, an isobutylamino group, a sec-butylamino group, a tert-butylamino group, an n-pentylamino group, an n-hexylamino group, an n-heptylamino group, an n-octylamino group, a 2-ethylhexylamino group, an n-nonylamino group, an n-decylamino group, a 3,7-dimethyloctylamino group, an n-dodecylamino group, a cyclopentylamino group, a dicyclopentylamino group, a cyclohexylamino group, a dicyclohexylamino group, a bis(trifluoromethyl)amino group, a phenylamino group, a diphenylamino group, a naphthylamino group, a pyridylamino group, a pyridazinylamino group, a pyrimidinylamino group, a pyrazinylamino group, and a triazinylamino group.

[0038] In the above general formula, when R is a group represented by -Si(R')3, the three R's may be the same or different, and it is preferable that at least one R' is a hydrocarbon group having 1 to 10 carbon atoms or a heterocyclic group which may have an alkyl group. Examples of the group represented by —Si(R′)3 include a trimethylsilyl group, a triethylsilyl group, a tri-n-propylsilyl group, a triisopropylsilyl group, a dimethylisopropylsilyl group, a diethylisopropylsilyl group, a tert-butyldimethylsilyl group, a n-pentyldimethylsilyl group, a n-hexyldimethylsilyl group, a n-heptyldimethylsilyl group, a n-octyldimethylsilyl group, a 2-ethylhexyldimethylsilyl group, a n-nonyldimethylsilyl group, a n-decyldimethylsilyl group, a 3,7-dimethyloctyldimethylsilyl group, a phenylalkylsilyl group, an alkoxyphenylalkylsilyl group, an alkylphenylalkylsilyl group, a naphthylalkylsilyl group, a phenylallyldimethylsilyl group, a triphenylsilyl group, a tri-p-xylylsilyl group, a tribenzylsilyl group, a diphenylmethylsilyl group, a tert-butyldiphenylsilyl group, and a dimethylphenylsilyl group.

[0039] When R in the above general formula is an acyl group, the acyl group is a group represented by R'CO-, where R' is as defined above. Examples of the acyl group include aliphatic acyl groups such as acetyl, propionyl, butyryl, and isobutyryl; and aromatic acyl groups such as benzoyl and naphthoyl.

[0040] In the above general formula, when R is a group having a carbon-nitrogen double bond, the group having a carbon-nitrogen double bond is an atomic group generated by removing one hydrogen atom directly bonded to the carbon or nitrogen atom that constitutes the carbon-nitrogen double bond in an imine compound. Examples of such imine compounds include aldimines, ketimines, and compounds in which the nitrogen atom that constitutes the carbon-nitrogen double bond in an aldimine has an alkyl group, an aryl group, an arylalkyl group, an arylalkenyl group, or an arylalkynyl group as a substituent.

[0041] Examples of the group having a carbon atom-nitrogen atom double bond include a group represented by -CR"=N-R"' and a group represented by -N=C(R'")2 (wherein R" represents a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, an arylalkyl group, an arylalkenyl group, or an arylalkynyl group, and one or two R'" each independently represent a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, an arylalkyl group, an arylcycloalkyl group, an arylalkenyl group, or an arylalkynyl group. However, in the group represented by -N=C(R'")2, two R'"s may be bonded to each other to form a divalent group (specifically, an alkylene group having 2 to 18 carbon atoms, such as an ethylene group, a trimethylene group, a tetramethylene group, a pentamethylene group, or a hexamethylene group). The group having a carbon atom-nitrogen atom double bond usually has 2 to 20 carbon atoms, preferably 2 to 18 carbon atoms, and more preferably 2 to 16 carbon atoms.

[0042] Examples of the group having a carbon atom-nitrogen atom double bond include the groups shown below. [ka]

[0043] When R in the above general formula is an acid imide group, the acid imide group is a group represented by (R'CO)2N-, where R' has the same meaning as above, and the two R's may be the same or different. The two R's may be bonded to each other to form a ring together with the carbon atom to which they are bonded and the nitrogen atom bonded to said carbon atom. The number of carbon atoms in the acid imide group is preferably 4 to 20, more preferably 4 to 18, and even more preferably 4 to 16.

[0044] Examples of the acid imide group include the groups shown below. [ka]

[0045] In the above general formula, when R is an alkoxycarbonyl group, the alkoxycarbonyl group is a group in which an alkoxy group is bonded to a carbonyl group. The alkoxy group has the same meaning as defined above. Examples of the alkoxycarbonyl group include a methoxycarbonyl group, an ethoxycarbonyl group, an n-propoxycarbonyl group, an isopropoxycarbonyl group, an n-butoxycarbonyl group, an isobutoxycarbonyl group, a sec-butoxycarbonyl group, a tert-butoxycarbonyl group, an n-pentyloxycarbonyl group, an n-hexyloxycarbonyl group, an n-heptyloxycarbonyl group, an n-octyloxycarbonyl group, a 2-ethylhexyloxycarbonyl group, an n-nonyloxycarbonyl group, an n-decyloxycarbonyl group, a 3,7-dimethyloctyloxycarbonyl group, an n-dodecyloxycarbonyl group, a trifluoromethoxycarbonyl group, a pentafluoroethoxycarbonyl group, a perfluorobutoxycarbonyl group, a perfluorohexyloxycarbonyl group, and a perfluorooctyloxycarbonyl group.

[0046] In the above general formula, when R is a cycloalkoxycarbonyl group, the cycloalkoxycarbonyl group is a group in which a cycloalkoxy group is bonded to a carbonyl group. The cycloalkoxy group has the same meaning as above. Examples of the cycloalkoxycarbonyl group include a cyclohexyloxycarbonyl group.

[0047] In the above general formula, when R is an aryloxycarbonyl group, the aryloxycarbonyl group is a group in which an aryloxy group is bonded to a carbonyl group. The aryloxy group has the same meaning as above. Examples of the aryloxycarbonyl group include a phenoxycarbonyl group, a naphthoxycarbonyl group, and a pyridyloxycarbonyl group.

[0048] In the above general formula (A), R 4 ~R 6 each independently represents a hydrogen atom, a fluorine atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms which may have a substituent, or a heteroaryl group having 4 to 20 carbon atoms which may have a substituent.

[0049] In the above general formula (A), R 4 ~R 6 may be configured such that all three are different, two are the same and one is different, or all three are the same. 4 ~R 6 Preferably, two are the same and one is different, or all three are the same.

[0050] R 4 ~R 6are each independently preferably an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms which may have a substituent, or a heteroaryl group having 4 to 20 carbon atoms which may have a substituent, and more preferably an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms, or an aryl group having 6 to 20 carbon atoms which may have a substituent.

[0051] Examples of the alkyl group having 1 to 20 carbon atoms include the aforementioned alkyl groups having 1 to 6 carbon atoms, as well as n-heptyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, n-octadecyl, n-nonadecyl, and n-icosyl groups. Among these, from the viewpoint of reactivity at low temperatures, alkyl groups having 1 to 6 carbon atoms are preferred, alkyl groups having 1 to 4 carbon atoms are more preferred, and tert-butyl is even more preferred.

[0052] Examples of alkenyl groups having 2 to 10 carbon atoms include vinyl, 1-propenyl, 2-propenyl, 1-butenyl, 2-butenyl, 3-methyl-2-butenyl, 1-pentenyl, 2-pentenyl, 1-hexenyl, 2-hexenyl, and 1-octenyl. Among these, from the viewpoint of reactivity at low temperatures, alkenyl groups having 2 to 8 carbon atoms are preferred, alkenyl groups having 2 to 6 carbon atoms are more preferred, 2-butenyl or 3-methyl-2-butenyl are even more preferred, and 2-butenyl is even more preferred. Note that R 4 ~R 6 When represents an alkenyl group having 2 to 10 carbon atoms, geometric isomers may exist. The geometric isomer may be either a cis isomer or a trans isomer, or a mixture of both may exist.

[0053] Examples of cycloalkyl groups having 5 to 10 carbon atoms include cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups. Of these, the cycloalkyl group having 5 to 10 carbon atoms is preferably a cycloalkyl group having 5 to 8 carbon atoms, and more preferably a cyclopentyl, cyclohexyl, cycloheptyl, or cyclooctyl group.

[0054] The definitions of the aryl group having 6 to 20 carbon atoms which may have a substituent and the heteroaryl group having 4 to 20 carbon atoms which may have a substituent are the same as those described above, and therefore further explanation will be omitted.

[0055] Preferred embodiments of the palladium complex of the present invention represented by the above general formula (A) include, for example, the following. (1)R 1 and R 2 is an alkyl group having 1 to 4 carbon atoms which may be substituted with a fluorine atom, and R 3 a palladium complex in which (2)R 1 and R 2 is an alkyl group having 1 to 4 carbon atoms, and R 3 a palladium complex in which (3)R 1 and R 2 is a methyl group, and R 3 a palladium complex in which (4)R 4 ~R 6 a palladium complex in which (5)R 4 ~R 6 a palladium complex in which the alkyl group is an alkyl group having 1 to 6 carbon atoms; (7)R 4 ~R 6 a palladium complex in which (8)R 4 ~R 6 a palladium complex in which (9)R 4 ~R 6a palladium complex in which the group is a cycloalkyl group having 5 to 10 carbon atoms; (10)R 4 ~R 6 a palladium complex in which the group is a cycloalkyl group having 5 to 8 carbon atoms; (11)R 4 ~R 6 a palladium complex in which (12)R 4 ~R 6 a palladium complex in which (13)R 4 ~R 6 a palladium complex in which (14)R 4 ~R 6 a palladium complex in which any two of the above are alkyl groups having 1 to 20 carbon atoms and the remaining one is an alkenyl group having 2 to 10 carbon atoms; (15)R 4 ~R 6 a palladium complex in which any two of the above are alkyl groups having 1 to 6 carbon atoms and the remaining one is an alkenyl group having 2 to 8 carbon atoms; (16)R 4 ~R 6 a palladium complex in which any two of the above are tert-butyl groups and the remaining one is a 2-butenyl group; (17)R 4 ~R 6 a palladium complex in which any two of the above are tert-butyl groups and the remaining one is a 3-methyl-2-butenyl group; (18)R 4 ~R 6 a palladium complex in which any two of the above are alkyl groups having 1 to 20 carbon atoms and the remaining one is a cycloalkyl group having 5 to 10 carbon atoms; (19)R 4 ~R 6 a palladium complex in which any two of the above are alkyl groups having 1 to 6 carbon atoms and the remaining one is a cycloalkyl group having 5 to 8 carbon atoms; (20)R 3 ~R 5a palladium complex in which any two of the above are tert-butyl groups and the remaining one is a cyclohexyl group; (21)R 4 ~R 6 a palladium complex in which any two of the above are alkyl groups having 1 to 20 carbon atoms, and the remaining one is an aryl group having 6 to 20 carbon atoms which may have a substituent; (22)R 4 ~R 6 a palladium complex in which any two of the above are alkyl groups having 1 to 6 carbon atoms, and the remaining one is an aryl group having 6 to 20 carbon atoms and having a substituent; (23)R 4 ~R 6 a palladium complex in which any two of the above are tert-butyl groups and the remaining one is a 4-(N,N-dimethylamino)phenyl group; (24) Palladium complexes in which X is a chlorine atom. These include, but are not limited to:

[0056] More preferred embodiments of the palladium complex of the present invention specifically include chloro(acetylacetonato)(tri-tert-butylphosphine)palladium, chloro(acetylacetonato)(tricyclopentylphosphine)palladium, chloro(acetylacetonato)(tricyclohexylphosphine)palladium, chloro(acetylacetonato)(di-tert-butylcrotylphosphine)palladium, chloro(acetylacetonato)(di-tert-butyl(3-methyl-2-butenyl)phosphine)palladium, chloro(acetyl acetonato)(di-tert-butyl(cyclopentyl)phosphine)palladium, chloro(acetylacetonato)(di-tert-butyl(cyclohexyl)phosphine)palladium, chloro(acetylacetonato)(di-tert-butyl(4-fluorophenyl)phosphine)palladium, chloro(acetylacetonato)(di-tert-butyl(3-fluorophenyl)phosphine)palladium, chloro(acetylacetonato)(di-tert-butyl(4-methylphenyl)phosphine)palladium, chloro(acetylacetonato)(di-tert-butyl(4-methylphenyl)phosphine)palladium, chloro(acetylacetonato) )(di-tert-butyl(3-methylphenyl)phosphine)palladium, chloro(acetylacetonato)(di-tert-butyl(4-ethylphenyl)phosphine)palladium, chloro(acetylacetonato)(di-tert-butyl(3-ethylphenyl)phosphine)palladium, chloro(acetylacetonato)(di-tert-butyl(4-isopropylphenyl)phosphine)palladium, chloro(acetylacetonato)(di-tert-butyl(3-isopropylphenyl)phosphine)palladium, chloro(acetylacetonato)(di-tert-butyl(3-isopropylphenyl)phosphine)palladium, chloro(acetylacetonato)(di-tert-butyl(4 ... chloro(acetylacetonato)(di-tert-butyl(4-tert-butylphenyl)phosphine)palladium, chloro(acetylacetonato)(di-tert-butyl(3-tert-butylphenyl)phosphine)palladium, chloro(acetylacetonato)(di-tert-butyl(4-methoxyphenyl)phosphine)palladium, chloro(acetylacetonato)(di-tert-butyl(3-methoxyphenyl)phosphine)palladium, chloro(acetylacetonato)(di-tert-butyl(2-methoxyphenyl)phosphine)palladium,Chloro(acetylacetonato)(di-tert-butyl(4-ethoxyphenyl)phosphine)palladium, Chloro(acetylacetonato)(di-tert-butyl(3-ethoxyphenyl)phosphine)palladium, Chloro(acetylacetonato)(di-tert-butyl(4-trifluoromethoxyphenyl)phosphine)palladium, Chloro(acetylacetonato)(di-tert-butyl(3-trifluoromethoxyphenyl)phosphine)palladium, Chloro(acetylacetonato)(di-tert-butyl(4-pentafluoro Chloro(acetylacetonato)(di-tert-butyl(3-pentafluoroethoxyphenyl)phosphine)palladium, Chloro(acetylacetonato)(di-tert-butyl([1,1'-biphenyl]-4-yl)phosphine)palladium, Chloro(acetylacetonato)(di-tert-butyl([1,1'-biphenyl]-3-yl)phosphine)palladium, Chloro(acetylacetonato)(di-tert-butyl(2-naphthyl)phosphine)palladium, Chloro(acetylacetonato)(di-tert-butyl(2-naphthyl)phosphine)palladium, acetonato)(di-tert-butyl(3,5-difluorophenyl)phosphine)palladium, chloro(acetylacetonato)(di-tert-butyl(3,5-dimethylphenyl)phosphine)palladium, chloro(acetylacetonato)(di-tert-butyl(3,5-diethylphenyl)phosphine)palladium, chloro(acetylacetonato)(di-tert-butyl(3,5-diisopropylphenyl)phosphine)palladium, chloro(acetylacetonato)(di-tert-butyl(3,5-di-tert-butyl phenyl)phosphine)palladium, chloro(acetylacetonato)(di-tert-butyl(3,5-dimethoxyphenyl)phosphine)palladium, chloro(acetylacetonato)(di-tert-butyl(3,5-diethoxyphenyl)phosphine)palladium, chloro(acetylacetonato)(di-tert-butyl(3,5-di-(trifluoromethoxy)phenyl)phosphine)palladium, chloro(acetylacetonato)(di-tert-butyl(3,5-di-(trifluoroethoxy)phenyl)phosphine)palladium,Examples of such chloro(acetylacetonato)(di-tert-butyl(2,3-dimethoxyphenyl)phosphine)palladium include chloro(acetylacetonato)(di-tert-butyl(2,4-dimethoxyphenyl)phosphine)palladium, chloro(acetylacetonato)(di-tert-butyl(2,5-dimethoxyphenyl)phosphine)palladium, chloro(acetylacetonato)(di-tert-butyl(2,6-dimethoxyphenyl)phosphine)palladium, and chloro(acetylacetonato)(di-tert-butyl(4-(N,N-dimethylamino)phenyl)phosphine)palladium.

[0057] Among the above, chloro(acetylacetonato)(tri-tert-butylphosphine)palladium, chloro(acetylacetonato)(tricyclohexylphosphine)palladium, chloro(acetylacetonato)(di-tert-butylcrotylphosphine)palladium, chloro(acetylacetonato)(di-tert-butyl(3-methyl-2-butenyl)phosphine)palladium, or chloro(acetylacetonato)(di-tert-butyl(4-(N,N-dimethylamino)phenyl group)phosphine)palladium are more preferred, and chloro(acetylacetonato)(tri-tert-butylphosphine)palladium represented by the following formula (A1), or chloro(acetylacetonato)(di-tert-butylcrotylphosphine)palladium represented by the following formula (A2) are particularly preferred.

[0058] [ka]

[0059] [Method of producing palladium complex] The method for producing a palladium complex of the present invention includes the steps of reacting a bis(β-diketonato)palladium complex with a phosphine compound represented by general formula (a) to obtain a reaction intermediate, and reacting the obtained reaction intermediate with hydrogen chloride, hydrogen bromide, or hydrogen iodide to obtain a palladium complex. [ka] (R in the formula 4 ~R 6 has the same definition as above, so the explanation will be omitted.)

[0060] A bis(β-diketonato)palladium complex is a complex compound in which two β-diketone residues are coordinated to one palladium atom. More specifically, it is a complex compound represented by the following general formula (b): [ka] (R in the formula 1 ~R 3 has the same definition as above, so the explanation will be omitted.)

[0061] The reaction intermediate can be obtained by dissolving the bis(β-diketonato)palladium complex in a solvent such as tetrahydrofuran (hereinafter referred to as "THF"), adding the phosphine compound represented by general formula (a), and heating and stirring as necessary. The phosphine compound represented by general formula (a) may be dissolved in a solvent and added. The solvent used here may be the same as or different from the solvent used to dissolve the bis(β-diketonato)palladium complex.

[0062] As for stirring conditions, the stirring time is usually 30 minutes to 3 hours. The stirring temperature is usually 20 to 50°C. Stirring may be carried out in the air or in an inert atmosphere such as nitrogen or argon. The reaction intermediate may be isolated or may be used in the next reaction without isolation.

[0063] The amount of the phosphine compound represented by the general formula (a) added is usually 0.5 to 2 mol, and preferably 1.0 to 1.2 mol, per 1 mol of the bis(β-diketonato)palladium complex. The amount of the solvent used is usually 1 to 10 ml per 1 g of the bis(β-diketonato)palladium complex.

[0064] When the phosphine compound represented by the general formula (a) is dissolved in a solvent, the amount of the solvent used is usually 1 to 10 ml per 1 g of the phosphine compound represented by the general formula (a).

[0065] The palladium complex can be obtained by adding hydrogen chloride, hydrogen bromide, or hydrogen iodide to the resulting reaction intermediate, and heating and stirring as necessary. The hydrogen chloride, hydrogen bromide, or hydrogen iodide may be added after being dissolved in water or a solvent such as dioxane.

[0066] As for stirring conditions, the stirring time is usually 30 minutes to 3 hours, and the stirring temperature is usually 20 to 50° C. Stirring may be carried out in the air or in an inert atmosphere such as nitrogen or argon.

[0067] The palladium complex can be isolated by distilling off the solvent.

[0068] The amount of hydrogen chloride, hydrogen bromide, or hydrogen iodide used is usually 2.0 to 2.2 mol per 1 mol of the bis(β-diketonato)palladium complex.

[0069] [Coupling reaction catalyst] The coupling reaction catalyst of the present invention comprises the above-described palladium complex. The reason why the coupling reaction catalyst comprising the palladium complex of the present invention exhibits excellent reaction activity at low temperatures, such as room temperature, is unclear. However, it is presumed that this is because, under catalytic reaction conditions, the 1,3-diketonato group coordinated to palladium promotes the reduction reaction of divalent palladium species to zero-valent palladium species, facilitating the generation of palladium(0) phosphine species that are highly active in coupling reactions. Furthermore, the use of an acetylacetonato group is thought to favorably generate palladium(0) phosphine species, facilitating the reaction.

[0070] As an example of using the above-mentioned palladium complex as a coupling reaction catalyst, in addition to the Suzuki-Miyaura coupling reaction described below, it can also be used in the following similar coupling reactions and chemical reactions. (a) Stille cross-coupling of organotin compounds with carbon electrophiles bearing halogens or pseudohalogens as leaving groups; (b) Hiyama cross-coupling of organosilanes with aryl, heteroaryl, or vinyl halides or pseudohalides; (c) Negishi cross-coupling of organozinc compounds with aryl, heteroaryl, or vinyl halides or pseudohalides; (d) Kumada cross-coupling of Grignard compounds with aryl, heteroaryl, or vinyl halides or pseudohalides; (e) Sonogashira cross-coupling of terminal alkynes with aryl, heteroaryl, or vinyl halides or pseudohalides; (f) α-arylation of enolates and other stabilized carbanions with aryl or heteroaryl halides or pseudohalides; (g) cyanation of aryl or heteroaryl halides or pseudohalides; (h) carbonylation of aryl or heteroaryl halides or pseudohalides; (i) Heck coupling of aryl, heteroaryl, or vinyl halides or pseudohalides to olefins.

[0071] [Method of producing aromatic compounds] The method for producing an aromatic compound of the present invention is a method for producing a carbon-carbon coupling reaction product (D) by subjecting an aromatic boronic acid compound (B) or an aromatic boronic acid ester (B') to a coupling reaction with an aromatic compound (C) in the presence of the above-mentioned palladium complex. The method for producing an aromatic compound of the present invention is a Suzuki-Miyaura coupling reaction in which a carbon-carbon bond is formed from an aromatic boronic acid compound (B) or an aromatic boronic acid ester (B') and an aromatic compound (C) to produce an aromatic compound.

[0072] The method for producing an aromatic compound of the present invention can produce the target compound under extremely mild conditions, such as room temperature and atmospheric pressure. Therefore, the method for producing an aromatic compound of the present invention is useful for producing information and electronic materials and pharmaceutical and agricultural intermediates, and is extremely valuable industrially.

[0073] The aromatic boronic acid compound (B) refers to a compound containing an aromatic ring and a boronic acid group in the molecule. Examples of the aromatic boronic acid compound (B) include acetylbenzeneboronic acid, aminobenzeneboronic acid, benzeneboronic acid, benzenediboronic acid, benzyloxybenzeneboronic acid, biphenylboronic acid, biphenyldiboronic acid, (trifluoromethoxy)benzeneboronic acid, (trifluoromethyl)benzeneboronic acid, bis(trifluoromethyl)benzeneboronic acid, carboxybenzeneboronic acid, carboxyethylbenzeneboronic acid, (carboxyvinyl)benzeneboronic acid, cyanobenzeneboronic acid, methoxybenzeneboronic acid, dimethoxybenzeneboronic acid, trimethoxybenzeneboronic acid, methylbenzeneboronic acid, dimethylbenzeneboronic acid, ethylbenzeneboronic acid, propylbenzeneboronic acid, butylbenzeneboronic acid, and pentylbenzeneboronic acid. Boronic acid, nonylbenzeneboronic acid, (methanesulfinyl)benzeneboronic acid, (methanesulfonyl)benzeneboronic acid, (ethanesulfonyl)benzeneboronic acid, (methylthio)benzeneboronic acid, (ethylthio)benzeneboronic acid, formylbenzeneboronic acid, formyl-methoxybenzeneboronic acid, hydroxybenzeneboronic acid, (hydroxymethyl)benzeneboronic acid cyclic monoester, (hydroxymethyl)benzeneboronic acid, vinylbenzeneboronic acid, (methoxycarbonyl)benzeneboronic acid, nitrobenzeneboronic acid, (nitrovinyl)benzeneboronic acid, isopropyl-methoxybenzeneboronic acid, (methylenedioxy)benzeneboronic acid, naphthaleneboronic acid, and methoxynaphthaleneboronic acid.

[0074] The aromatic boronic acid ester (B') refers to a compound containing an aromatic ring and a boronic acid ester group in the molecule. Examples of the aromatic boronic acid ester (B') include compounds that form an ester structure with one or two boronic acid groups of the aromatic boronic acid compound (B). The ester structure may also be a ring structure containing two oxygen atoms, in which the same molecule forms an ester structure with two hydroxyl groups of the boronic acid group.

[0075] Examples of the aromatic boronic acid ester (B′) include 5,5-dimethyl-2-phenyl-1,3,2-dioxaborinane, 5,5-dimethyl-2-(4-fluorophenyl)-1,3,2-dioxaborinane, methyl 3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoate, dimethyl 5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzene-1,3-dicarboxylate, 4,4,5,5-tetramethyl-2-(2-azulenyl)-1,3,2-dioxaborolane, and 5,5-dimethyl-2-(2,4,6-trimethylphenyl)-1,3,2-dioxaborinane.

[0076] The aromatic ring of the aromatic boronic acid compound (B) or the aromatic boronic acid ester (B') may have a suitable substituent, such as an alkyl group (e.g., an alkyl group having 1 to 10 carbon atoms), an alkenyl group (e.g., an alkenyl group having 2 to 10 carbon atoms), an alkynyl group (e.g., an alkynyl group having 2 to 10 carbon atoms), an alkoxy group (e.g., an alkoxy group having 1 to 10 carbon atoms), a hydroxyl group, an amino group, a mono- or dialkylamino group, a carboxyl group, an alkoxycarbonyl group (e.g., an alkoxycarbonyl group having 1 to 10 carbon atoms), a cyano group, a nitro group, a group containing silicon (e.g., a trialkylsilyl group), Examples of the aromatic ring include acyl groups (e.g., acetyl and formyl groups), aminocarbonyl groups, aryl groups (e.g., phenyl groups), heteroaryl groups (e.g., pyridyl, pyrrolyl, and furyl groups), phosphorus-containing groups (e.g., dialkylphosphino, diarylphosphino, dialkylphosphoryl, diarylphosphoryl, dialkoxyphosphoryl, and diaryloxyphosphoryl groups), and sulfur-containing groups (e.g., thienyl, sulfo, sulfino, and sulfeno groups). The aromatic ring may have 1 to 3 substituents selected from the above-listed substituents.

[0077] The aromatic compound (C) refers to an aromatic compound other than the aromatic boronic acid compound (B) or the aromatic boronic acid ester (B'), which can be used to produce a carbon-carbon coupling reaction product with the aromatic boronic acid compound (B) or the aromatic boronic acid ester (B'). Examples of the aromatic compound (C) include halogenated aromatic compounds such as 1-bromo-4-nitrobenzene, p-bromoanisole, o-bromotoluene, 1-bromo-2,4,6-trimethylbenzene, 4-bromo-2,6-dichlorophenol, 2-bromobenzonitrile, and 4,7-dibromo-2-alkyl-2H-benzotriazole.

[0078] The aromatic ring of the aromatic compound (C) may have a suitable substituent, such as an alkyl group (e.g., an alkyl group having 1 to 10 carbon atoms), an alkenyl group (e.g., an alkenyl group having 2 to 10 carbon atoms), an alkynyl group (e.g., an alkynyl group having 2 to 10 carbon atoms), an alkoxy group (e.g., an alkoxy group having 1 to 10 carbon atoms), a hydroxyl group, an amino group, a mono- or dialkylamino group, a carboxyl group, an alkoxycarbonyl group (e.g., an alkoxycarbonyl group having 1 to 10 carbon atoms), a cyano group, a nitro group, a group containing silicon (e.g., a trialkylsilyl group), Examples of the aromatic ring include acyl groups (e.g., acetyl and formyl groups), aminocarbonyl groups, aryl groups (e.g., phenyl groups), heteroaryl groups (e.g., pyridyl, pyrrolyl, and furyl groups), phosphorus-containing groups (e.g., dialkylphosphino, diarylphosphino, dialkylphosphoryl, diarylphosphoryl, dialkoxyphosphoryl, and diaryloxyphosphoryl groups), and sulfur-containing groups (e.g., thienyl, sulfo, sulfino, and sulfeno groups). The aromatic ring may have 1 to 3 substituents selected from the above-listed substituents.

[0079] In the method for producing an aromatic compound of the present invention, the coupling reaction may be carried out in the coexistence of a base. Either an organic base or an inorganic base can be used as the base that may be coexisted in the method for producing an aromatic compound of the present invention.

[0080] Examples of organic bases include amines such as triethylamine, pyridine, aniline, 1,5-diazabicyclo[4.3.0]non-5-ene, 1,4-diazabicyclo[2.2.2]octane, and 1,8-diazabicyclo[5.4.0]-7-undecene. Examples of inorganic bases include hydroxides, fluorides, carbonates, hydrogen carbonates, and phosphates of alkali metals (lithium, sodium, potassium, rubidium, cesium, etc.) or alkaline earth metals (beryllium, magnesium, calcium, strontium, barium, etc.). More specific examples include sodium carbonate, potassium carbonate, tripotassium phosphate, trisodium phosphate, sodium hydrogen carbonate, and sodium metaborate. The bases exemplified above may be used alone or in combination of two or more.

[0081] The amount of base added can be in the range of 0.1 to 10 moles, or may be in the range of 0.5 to 3 moles, per mole of the aromatic compound (C) which is one of the reactants.

[0082] In the method for producing an aromatic compound of the present invention, the coupling reaction may be carried out appropriately in the presence of an inorganic salt such as sodium chloride as another optional component.

[0083] The method for producing an aromatic compound of the present invention is not particularly limited, and known coupling reactions can be used as appropriate. It is also preferable to use Suzuki-Miyaura coupling in the method for producing an aromatic compound of the present invention. By using the method for producing a carbon-carbon coupling product, the solid catalyst and the product can be easily separated during or after the reaction, even in Suzuki-Miyaura coupling and the like.

[0084] The molar ratio of the aromatic boronic acid compound (B) or the aromatic boronic acid ester (B') to the aromatic compound (C) used can be 0.5 to 10:1, or may be 0.8 to 2:1, where [aromatic boronic acid compound (B) or the aromatic boronic acid ester (B')]:[aromatic compound (C)].

[0085] The solvent used in the method for producing an aromatic compound of the present invention is not particularly limited, and examples thereof include methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dioxane, cyclohexanone, n-hexane, diethyl ether, diisopropyl ether, n-butyl methyl ether, t-butyl methyl ether, benzene, toluene, xylene, cumene, cymene, mesitylene, diisopropylbenzene, pyridine, pyrimidine, pyrazine, pyridazine, methanol, ethanol, n-propyl alcohol, isopropyl alcohol, butanol, aminoethanol, N,N-dimethylaminoethanol, chloroform, dichloromethane, carbon tetrachloride, dichloroethane, trichloroethane, dimethyl sulfoxide (DMSO), dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), dimethoxyethane (DME), and water. Among these, preferred are water; C1-6 alcohols such as methanol, ethanol, and isopropyl alcohol; aromatic hydrocarbons such as toluene; polar organic solvents such as 1,4-dioxane; or combinations thereof. Among these, a mixed solvent of toluene and water is more preferable. When a mixed solvent of toluene and water is used, the volume ratio of toluene to water is preferably in the range of 1:9 to 9:1.

[0086] In the method for producing an aromatic compound of the present invention, the amount of the palladium complex used can be in the range of 0.001 to 20 mol %, alternatively 0.01 to 10 mol %, or alternatively 0.05 to 5 mol %, in terms of palladium, relative to the aromatic compound (C), which is one of the reactants.

[0087] In the method for producing an aromatic compound of the present invention, the coupling reaction can be carried out, for example, in an air atmosphere or an inert gas atmosphere such as nitrogen or argon, but is preferably carried out in an inert gas atmosphere.

[0088] The reaction temperature for the coupling reaction is preferably 40° C. or lower, more preferably 20 to 40° C., and even more preferably room temperature to 40° C. The reaction time can be set arbitrarily within the range of 0.1 to 48 hours.

[0089] By using the palladium complex of the present invention as a catalyst for the above-mentioned coupling reaction, the coupling reaction can proceed in a short time even under mild reaction conditions, and the target product can be obtained in high yield. [Example]

[0090] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0091] <Raw material: Palladium complex> (Production Example A-1: Chloro(acetylacetonato)(tri-t-butylphosphine)palladium(II): [PdCl(acac)(PtBu)]) In a 100 mL eggplant-shaped flask thoroughly purged with nitrogen, 3.6 g of bis(acetylacetonato)palladium complex and 15 mL of tetrahydrofuran were added. 4.8 g of a 50% tri-t-butylphosphine toluene solution was added and stirred for 60 minutes. Next, 3 mL of a 4 M HCl dioxane solution was added and stirred for 2 hours. The solvent was removed using an evaporator and the mixture was washed with 10 mL of hexane. The resulting solid was dried and 1 H NMR, 13 C NMR and 31 Evaluation by P NMR revealed that the target chloro(acetylacetonato)(tri-t-butylphosphine)palladium(II) was obtained. The structure of the obtained palladium complex is shown below. The production ratio (yield) of the product relative to the palladium raw material was 77%. 1H NMR (400 MHz, CDCl3) peak positions: 5.39 (1H, s), 2.06 (3H, s), 1.91 (3H, s), 1.68 (27H, d, J = 12.8 Hz). 13 C NMR (100 MHz, CDCl3) peak positions: 187.3, 182.2, 99.8, 41.5, 33.3, 27.2, 25.7. 31 P NMR (162 MHz, CDCl3) peak position: 77.7.

[0092] [ka]

[0093] (Production Example A-2: Chloro(acetylacetonato)(di-t-butylcrotylphosphine)palladium(II): [PdCl(acac)(Crophos)]) The target chloro(acetylacetonato)(di-t-butylcrotylphosphine)palladium(II) was obtained in the same manner as in Preparation A-1, except that 2.5 g of di-t-butylcrotylphosphine was used instead of the 50% tri-t-butylphosphine toluene solution. 1 H NMR and 31 The evaluation results of P NMR are shown below. The production ratio (yield) of the product relative to the palladium raw material was 33%. 1 H NMR (400MHz, CDCl3) peak position: 5.63(1H,m), 3.75(2H,m), 2.66(2H,s), 1.79(3H,s), 1.62(6H,s), 1.52(18H,d,J=12.8Hz). 31 P NMR (162 MHz, CDCl3) peak position: 71.8.

[0094] [ka]

[0095] (Production Example B-1: Chloro(allyl)(di-t-butylcrotylphosphine)palladium(II): [PdCl(C3H5)(Crophos)]) A 25 ml eggplant-shaped flask, thoroughly purged with nitrogen, was charged with 3 ml of tetrahydrofuran and 0.9 g of di-μ-chlorobis[(η-allyl)palladium(II)]. 1.0 g of di-t-butylcrotylphosphine was then charged and stirred for 1 hour. The solvent was removed using an evaporator and the mixture was washed with 10 mL of hexane. The resulting solid was dried to obtain the desired chloro(allyl)(di-t-butylcrotylphosphine)palladium(II). The structure of the resulting palladium complex is shown below. The yield of the product relative to the palladium raw material was 45%.

[0096] [ka]

[0097] (B-2: Dichlorobis(di-t-butylcrotylphosphine)palladium(II): [PdCl2(Crophos)2]) Manufactured by N.E. Chemcat Corporation, the product name is NECO-295. The structure is shown below. [ka]

[0098] (B-3: Dichlorobis(di-t-butyl(3-methyl-2-butenyl)phosphine)palladium(II): [PdCl2(m-Crophos)2]) Manufactured by N.E. Chemcat, the product name is NECO-296. The structure is shown below. [ka]

[0099] (B-4: Dichlorobis(tricyclohexylphosphine)palladium(II): [PdCl2(PCy3)2]) The product name is "PdCl2(PCy3)2" manufactured by N.E. Chemcat Corporation. The structure is shown below. [ka]

[0100] (B-5: Chlorophenylallyl[1,3-bis(diisopropylphenyl)-2-imidazolidinylidene]palladium(II): [PdCl(cinnamyl)(SIpr)] The product name is CX-32, manufactured by Umicore. The structure is shown below. [ka]

[0101] <Reaction: Method for producing aromatic compounds> Example 1 One equivalent of 4-bromoanisole, 1.1 equivalents of phenylboronic acid, 0.001 equivalents of Pd complex (A-1), and 1.2 equivalents of tripotassium phosphate were mixed in a toluene / water mixed solvent (volume ratio 1:9) and stirred at room temperature for 1 hour. The resulting reaction mixture was quantitatively analyzed using gas chromatography. The yield of the target product, 4-methoxybiphenyl, was 99% based on the raw material, 4-bromoanisole.

[0102] <Example 2 and Comparative Examples 1 to 5> Evaluation was carried out in the same manner as in Example 1, except that the palladium complex (A-1) was changed as shown in Table 1. Table 1 shows the yield of the target product obtained in each example and comparative example.

[0103] [Table 1]

[0104] As is clear from Table 1, when the palladium complex (coupling reaction catalyst) of the present invention is used, the coupling reaction proceeds in a short time of 1 hour even under mild reaction conditions such as room temperature, and the target product can be obtained in high yield. Therefore, the palladium complex (coupling reaction catalyst) of the present invention is useful for producing information and electronic materials and pharmaceutical and agricultural intermediates, and can be said to be extremely valuable industrially.

Claims

1. A palladium complex represented by the following general formula (A): 【Chemical 1】 (In the formula, X represents a chlorine atom, a bromine atom, or an iodine atom; R １ ~R ３ each independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms which may be substituted with a fluorine atom, an aryl group having 6 to 20 carbon atoms which may have a substituent, or a heteroaryl group having 4 to 20 carbon atoms which may have a substituent; R ４ ~R ６ each independently represents a hydrogen atom, a fluorine atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms which may have a substituent, or a heteroaryl group having 4 to 20 carbon atoms which may have a substituent; Substituents which the aryl group and heteroaryl group may have include a fluorine atom, an alkyl group, a cycloalkyl group, an alkoxy group, a cycloalkoxy group, an alkylthio group, a cycloalkylthio group, an aryl group, an aryloxy group, an arylthio group, an arylalkyl group, an arylcycloalkyl group, an arylalkenyl group, an arylalkynyl group, a heterocyclic group which may have an alkyl group, -N(R') ２ (wherein, each of the two R's independently represents a hydrogen atom, a hydrocarbon group having 1 to 10 carbon atoms, or a heterocyclic group which may have an alkyl group), -Si(R') ３ (wherein R' has the same meaning as defined above, and the three R' may be the same or different), an acyl group, a group having a carbon-nitrogen double bond, an acid imide group, an alkoxycarbonyl group, a cycloalkoxycarbonyl group, an aryloxycarbonyl group, a carboxy group, a cyano group, a nitrile group, and a nitro group; R ４ ~R ６ All three of the above represent phenyl groups, and R ４ ~R ６ Any two of these do not represent methyl groups and the remaining one does not represent a phenyl group.)

2. R in the general formula (A) １ and R ２ is a methyl group, and R ３ The palladium complex according to claim 1 , wherein is a hydrogen atom.

3. 3. The palladium complex according to claim 1, wherein X in the general formula (A) is a chlorine atom.

4. R in the general formula (A) ４ ~R ６ The palladium complex according to any one of claims 1 to 3, wherein one or more of the following is a tert-butyl group.

5. R in the general formula (A) ４ ~R ６ 5. The palladium complex according to claim 1, wherein at least one of the following is a substituted aryl group, a substituted alkenyl group having 2 to 6 carbon atoms, or a substituted cycloalkyl group having 5 to 8 carbon atoms.

6. The palladium complex according to any one of claims 1 to 5, which is represented by the following formula (A1) or (A2): 【Chemistry 2】

7. A coupling reaction catalyst comprising the palladium complex according to any one of claims 1 to 6.

8. A method for producing a palladium complex represented by general formula (A) according to claim 1, comprising: A step of reacting a bis(β-diketonato)palladium complex with a phosphine compound represented by the following general formula (a) to obtain a reaction intermediate; and reacting the reaction intermediate with hydrogen chloride, hydrogen bromide, or hydrogen iodide to obtain the palladium complex; A method for producing a palladium complex, comprising: 【Chemistry 3】 (In the formula, R ４ ~R ６ has the same definition as in claim 1.)

9. A method for producing an aromatic compound, comprising: subjecting an aromatic boronic acid compound (B) or an aromatic boronic acid ester (B') to a coupling reaction with a halogenated aromatic compound (C) in the presence of the palladium complex according to any one of claims 1 to 6 to produce a carbon-carbon coupling reaction product (D).

10. The method according to claim 9, wherein the reaction temperature of the coupling reaction is 40°C or lower.

Images