JPH053857B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing a dimer of an aromatic compound in high yield by dehalogenating and dimerizing an aromatic halogen compound. [Prior art] Dimers of aromatic compounds are useful as various industrial raw materials, for example, 3,4,3',4'-
Biphenyltetracarboxylic acid alkali metal salt is
It is very useful as a raw material for heat-resistant polyimide resin. Conventionally, as a method for producing biphenyl compounds by dehalogenating and dimerizing aromatic halogen compounds, for example, dehalogenation is carried out in an aqueous alkali hydroxide solution in the presence of a catalyst supporting metal palladium (Pd-supported catalyst) and methanol. Dimerization method (J.Am.Chem.Soc, 71 776 (1949), Special Publication No. 14015/1983) or palladium supported on activated carbon,
Dimerization method using sodium carbonate and methanol solvent or dioxane-ethylene glycol mixed solvent, (Bull.Soc.Chim.Fr.2791
(1973)) is known. However, according to these known methods, the yield of biphenyl compounds is low, and in some cases,
A large amount of dehalogenated aromatic compound monomer was produced as a by-product, and the selectivity for the desired biphenyl compound was low. [Problems to be Solved by the Invention] The present inventors have conducted intensive research on a method for producing biphenyl compounds in high yield and with good selectivity by dehalogenating and dimerizing aromatic halogen compounds, and as a result, a palladium catalyst has been developed. The present inventors have discovered that biphenyl compounds can be produced in high yield and with good selectivity by reacting in the presence of water, polyhydric alcohols, and/or formaldehydes, and have completed the present invention. [Means for Solving the Problems] The gist of the present invention is to dehalogenate an aromatic compound having at least one halogen atom in the aromatic carbon in the presence of a palladium catalyst, water, and a polyhydric alcohol and/or formaldehyde. The present invention relates to a method for dehalogenating and dimerizing aromatic halogenated compounds, which is characterized by dimerization. The present invention will be explained in detail below. Aromatic compounds having at least one halogen atom on the aromatic carbon are used as starting materials in the process of the invention. Examples of the at least one halogen atom in the aromatic carbon include iodine, bromine, and chlorine, with bromine and chlorine being preferred, and chlorine being particularly inexpensive. When two or more halogen atoms are substituted in the aromatic nucleus of the aromatic compound, the halogens may be the same or different. Also, the number of halogen atoms is 6
If the number of halogen atoms is large, dimerization and dehalogenation may occur, but the number of halogen atoms is preferably 3 or less. The core carbon of this aromatic compound can have a substituent other than the at least one halogen atom, but when the carbon adjacent to the halogen atom has another substituent or when multiple halogen atoms are adjacent, may reduce the yield of biphenyl compounds. Specific examples of the aromatic halogen compound used in the method of the present invention include, for example, chlorobenzene,
p-chlorobromobenzene, p-chlorodiphenyl, p-chlorophenol, p-chloroanisole, p-chlorobenzamide, p-chloroaniline, p-chloronitrobenzene, p-chlorobenzophenone, p-chloroacetophenone, p-
Chlorobenzenesulfonic acid sodium salt, p-chlorobenzoic acid, p-chlorobenzonitrile, β-
Chloronaphthalene, 4-chloroorthoxylene,
Examples include alkali metal hydrochloric anhydrides such as lithium, sodium, and potassium of 4-chloroorthophthalic acid, and 4,5-dichlorophthalic acid. Examples of the palladium catalyst used in the present invention include inorganic acid palladium salts such as palladium chloride and palladium nitrate, organic acid palladium salts such as palladium acetate and palladium phthalate, palladium chelate salts containing β-diketones such as acetylacetone, and metal palladium. It will be done. Among these, those supported on carriers such as metal palladium activated carbon, silica, alumina, silica alumina, titanium oxide, magnesia, diatomaceous earth, graphite, barium carbonate, calcium carbonate, and zeolite are preferred, and palladium-activated carbon catalysts are particularly preferred. be. The metal palladium supported on these palladium-carrier catalysts is 0.1 to 20% by weight based on the palladium-carrier.
In particular, it is preferable that the amount supported is about 0.5 to 10% by weight. The amount of palladium catalyst used is 100 to 100 palladium atoms per mole of aromatic halogen compound.
0.001 milligram atom, preferably 30-0.1 milligram atom. In the method of the present invention, it is important that water, polyhydric alcohol and/or formaldehyde be present in the reaction system consisting of the aromatic halogen compound and palladium catalyst. When the aromatic halogen compound is water-soluble, water is used either as an aqueous solution containing the aromatic halogen compound or by directly adding it to the reaction system. The amount of water used is at least 0.1% by volume, preferably 1% by volume, based on the reaction medium containing aromatic halogen compound, palladium catalyst, polyhydric alcohol and/or formaldehyde and optionally halogen acceptor and solvent as described below. Capacity% or more is required. When the aromatic halogen compound is water-soluble, it is preferable to use a solvent amount. On the other hand, in the case of water-insoluble compounds, the use of a large amount of water may actually reduce the yield of the biphenyl compound, so the amount of water used is preferably selected from the range of 1 to 60% by volume. If the amount of water used is less than the above range or if water is not added, the yield and selectivity of the biphenyl compound will decrease, which is not preferable. The polyhydric alcohols used in the present invention include ethylene glycol, propylene glycol, 1,
Examples include dihydric alcohols such as 2-butanediol, 1,3-propanediol, and 1,4-butanediol, trihydric alcohols such as glycerin, and tetrahydric alcohols such as pentaerythritol. Among them, ethylene glycol, propylene glycol, 1,2-butanediol, glycerin, etc.
Hydrolic or trihydric alcohols are preferred. The amount of polyhydric alcohol used is 0.01 to 50 mol, preferably 0.5 to 10 mol, per 1 mol of aromatic halogen compound. Outside the above range, the yield of the biphenyl compound decreases, which is not preferable. As for how to use these polyhydric alcohols, a predetermined amount within the above range may be added at once, or they may be supplied continuously or intermittently during the dehalogen dimerization reaction. As the formaldehyde used in the present invention, paraformaldehyde and commercially available 35% formalin solution are suitable. The amount of formaldehyde used is 0.01 to 50 mol, preferably 0.5 to 10 mol, per 1 mol of the aromatic halogen compound on a monomer basis. In the method of the present invention, it is preferable to use a halogen receptor in combination. The halogen acceptor may be any substance that can accept halogen atoms generated during the dehalogen dimerization reaction, and is usually an organic base or an inorganic base. Examples of organic bases include tertiary amines such as triethylamine, tributylamine, and trioctylamine;
Examples of the inorganic base include alkali metal compounds and alkaline earth metal compounds. Among these, alkali metal compounds are preferred, and specific examples include inorganic acid salts of alkali metals such as carbonic acid, phosphoric acid, and boric acid, hydroxides, organic acid salts such as acetic acid, and phthalic acid, and alkoxides. It will be done. Particularly preferred examples include lithium hydroxide, sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate, sodium methoxide, potassium tertiary butyrate, and the like. The amount of these halogen acceptors to be used varies depending on the number of halogen atoms contained in the aromatic halogen compound as a starting material and the presence of other optional substituents such as carboxyl groups, but usually per mole of the aromatic halogen compound. 0.01 to 100 mol, preferably 1 to 10 mol, is used. If the amount used is outside the above range, the yield of the biphenyl compound will decrease, which is undesirable. The method of the present invention can be carried out either in the presence or absence of a solvent, but when a solvent is used, it is carried out in the presence of a solvent that is inert to the reaction. Examples of such solvents include ether compounds such as tetrahydrofuran and dioxane, ketone compounds such as acetone, diethyl ketone, and methyl ethyl ketone;
It is selected from ester compounds such as ethylene glycol diacetate, water, and the like. The amount of such a solvent used is not particularly limited, but is usually 0.01 to 1 part per part of the aromatic halogen compound.
Selected from a range of 100 copies. In the method of the present invention, a mixture of the aromatic halogen compound, palladium catalyst, water, and polyhydric alcohol and/or formaldehyde is heated to 40 to 250°C, preferably 50 to 200°C, in the absence or presence of a solvent. Do this by heating. The reaction pressure is normal pressure ~ 200Kg/cm ³ , preferably normal pressure ~
It is carried out in the range of 100 Kg/cm ³ and, if necessary, in the presence of an inert gas. The reaction time is not particularly limited and is appropriately selected depending on the type of raw materials, amount of catalyst, reaction temperature, pressure, etc., but is usually about 10 minutes to 24 hours. The method of the present invention can be carried out in batches, half batches, or continuously. After the reaction, the palladium catalyst used in the reaction is separated and recovered from the reaction solution by conventional methods such as extraction, crystallization, or reduction. When a palladium-supported catalyst is used, it can be easily separated and recovered by filtration and used again in the dehalogenation dimerization reaction. The biphenyl compound obtained in the present invention is separated and obtained from the reaction solution by evaporation, distillation, crystallization method, acid precipitation method, etc. according to its physical properties. [Effects of the Invention] According to the method of the present invention, biphenyl compounds can be obtained in high yield and with good selectivity by allowing a small amount of polyhydric alcohol and/or formaldehyde to be present in the reaction system, making it extremely useful industrially. It's a method. [Examples] Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded. Examples 1 and 2 0.2 g of 2% palladium carbon (manufactured by Engelhard Japan) was placed in a Hastelloy spinner-stirred microautoclave with an internal volume of 70 ml, and 4-chlorophthalic anhydride (hereinafter referred to as 4-CPA) was added to 15 ml of distilled water.
) 1.86g (0.1g of phthalic anhydride as an impurity)
and 0.04 g of dichlorophthalic anhydride were mixed. ) and 2 g of sodium hydroxide completely dissolved in an aqueous solution and a specified amount of ethylene glycol, the autoclave was sealed, and the autoclave was heated at 60°C for 2 hours.
The reaction was allowed to proceed for 30 minutes. After the reaction, liquid chromatography analysis revealed that the reaction solution contained dehalogenated orthophthalic acid sodium salt (hereinafter abbreviated as PA salt) and the desired sodium 3,4,3',4'-biphenyltetracarboxylate. Salt (hereinafter referred to as S-BTC
(abbreviated as salt) was produced. The results are shown in Table-1. Comparative Examples 1, 2, 3 The same procedure as Example 1 was carried out except that a predetermined amount of methanol was used instead of ethylene glycol.
The results are shown in Table-1.

[Table] Example 3 The same procedure as in Example 1 was carried out except that 40 mmol of 1,2-butanediol was used instead of ethylene glycol. The 4-CPA conversion rate was 49%, the S-BTC salt yield was 26.4%, and the S-BTC salt selectivity was 54%. Example 4 The same procedure as in Example 1 was carried out except that 40 mmol of glycerin was used instead of ethylene glycol and the reaction was carried out at 100° C. for 1 hour and 30 minutes. 4-CPA conversion rate 100%, S-BTC salt yield 50.3%
It was hot. Example 5 The same procedure as Example 4 was carried out except that paraformaldehyde was used instead of glycerin. The 4-CPA conversion rate was 100% and the S-BTC salt yield was 38%. Example 6 In the same manner as in Example 1, chlorobenzene
3.377g, 5% palladium carbon 1.06g, sodium carbonate 3.18g, ethylene glycol 10ml,
Prepare 10ml of distilled water and 10ml of dioxane and heat to 100°C.
The mixture was allowed to react for 8 hours. The conversion rate of chlorobenzene was 68.6%, the yield of biphenyl was 52%, and the selectivity of biphenyl was 76%. Comparative Example 6 The same procedure as in Example 6 was carried out except that 20 ml of dioxane was used instead of distilled water. The conversion rate of chlorobenzene was 94.9%, the yield of biphenyl was 49%, and the selectivity of biphenyl was 52%. Example 7 The same procedure as Example 6 was carried out except that 4.219 g of 4-chloroorthoxylene was used instead of chlorobenzene. Conversion rate of 4-chloroorthoxylene 49.6%,
Yield of 3,4,3',4'-tetramethylbiphenyl
It was 25.9%.

Claims (1)

[Claims] 1 Dehalogenation and dimerization of aromatic halogenated compounds having at least one halogen atom in the aromatic carbon in the presence of a palladium catalyst, water, polyhydric alcohol and/or formaldehyde Halogen dimerization method.