JPH0243387A - Method for producing 4,4'-dihydroxybiphenyls - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing 4,4'-dihydroxybiphenyls.

4.4'-Dihydroxybiphenyls are useful as fungicides, synthetic intermediates, and antioxidants.

For example, the 3.3',5.5'-tetra-substituted 4.4
'-Dihydroxybiphenyl is used to stabilize oils and fats, gasoline, lubricating oils, rubber compositions, etc.

[Conventional technology]

Various methods have been developed for reducing easily available 4,4'-diphenoquinones to 4.4'-dihydroxybiphenyls. For example, the following methods are known.

■ A method for obtaining 4,4'-dihydroxybiphenyls by reducing 4.4'-diphenoquinones with hydrogen in the presence of a noble metal catalyst (US Pat. No. 4,482,755), ■ 4.4'-
A method for obtaining 4,4'-dihydroxybiphenyls by reacting diphenoquinones with alkylphenols at high temperatures (Tetrahedron Lett4241 (1)
965), ), (2) Reduction of 4.4'-diphenoquinones with zinc powder in acetic acid to obtain the corresponding biphenols (US Pat. No. 2,785,188).

Various other methods have been proposed.

[Problem to be solved by the invention]

However, these conventional methods each have the following drawbacks when put into practical use.

In other words, the above method (①) has problems with catalyst life, as well as
It is disadvantageous in that it requires pressurizing equipment.

The method (2) above requires a very high temperature, so there are problems with the purity of the product.

The method (2) above requires a larger amount of zinc powder than the equivalent amount, which poses a problem in terms of cost.

Therefore, it has been desired to develop a method for easily producing 4,4'-dihydroxybiphenyls, which are useful as synthetic intermediates, in a high yield under mild conditions.

[Means to solve the problem]

The present inventors have completed the present invention as a result of extensive studies aimed at solving the above problems and developing a method for industrially advantageous production of 4,4' dihydroxybiphenyls.

That is, the present invention provides general formula (I): (wherein, R+, Rg, R3 and R4 have 1 to 1 carbon atoms;
4,4'-diphenoquinones represented by 12 alkyl groups or hydrogen atoms (which may be different from each other) with (i) a lower aliphatic alcohol or (ii) an organic solvent that is miscible with the lower aliphatic alcohol. 4,4'-dihydroxybiphenyls represented by the general formula (■): (wherein R,, R,, R8 and R4 are the same as above) are electrolytically reduced in a mixture with a lower aliphatic alcohol. A method for producing 4,4'-dihydroxybiphenyls, characterized by obtaining the following.

The present invention will be explained in more detail below.

The 4,4'-diphenoquinones used in the method of the present invention have the general formula (f): (wherein R,, R2, R3 and R4 have 1 to 12 carbon atoms.
represents an alkyl group or a hydrogen atom (which may be different from each other). The alkyl group in the above general formula (1) may be linear or may have a side chain.

Specifically, for example, 3,5.3',5'-tetramethyldiphenoquinone, 353'5'tetraethyldiphenoquinone, 3,5.3',5'tetra-t-butyldiphenoquinone, 33 '-Dimethyl-55'-di-t-butyldiphenoquinone, 3,3'-dimethyl-5,5'-dioctyldiphenoquinone, 3,3'-dimethyldiphenoquinone, 33'-di-t- Examples include butyl diphenoquinone.

Further, the above-mentioned 4,4'-diphenoquinones can be produced by various methods, and for example, they can be easily produced by oxidative coupling of alkylphenols by a known method.

In the method of the present invention, the above-mentioned 4,4'-diphenoquinones are subjected to an electrolytic reduction reaction in a specific solvent to produce 4,4'-diphenoquinones.
Dihydroxybiphenyls are obtained.

The electrolytic cell to be used is not particularly limited;
The electrolytic cell may be either a diaphragm type electrolytic cell in which the anode chamber and the cathode chamber are partitioned by a diaphragm, or a non-diaphragm type electrolytic cell in which the anode chamber and the cathode chamber are not partitioned by a diaphragm.

The electrode material is not particularly limited, and known materials can be used. Examples of cathode materials include platinum, carbon, Francie carbon, stainless steel, lead, nickel,
Examples include aluminum, zinc, and other processed electrodes. As the anode material, for example, platinum, carbon, Francie carbon, lead oxide, lead, stainless steel, nickel, aluminum, zinc, and other processed electrodes can be used.

The diaphragm of the diaphragm type electrolytic cell is not particularly limited.
Known ion exchange membranes, inorganic porous membranes, etc. can be used.

The solvent used in the electrolytic reduction reaction in the method of the present invention is preferably one that can dissolve the 4,4'-diphenoquinones as raw materials and the 4,4'-dihydroxybiphenyls as products, and also dissolve the supporting electrolyte described below. Therefore,
1) a lower aliphatic alcohol or ii) a mixture of the lower aliphatic alcohol and an organic solvent miscible with the lower aliphatic alcohol is used.

It is preferable to carry out the reaction in a lower aliphatic alcohol from the viewpoint of selectivity of the desired product. The lower aliphatic alcohol is preferably an alcohol having 1 to 4 carbon atoms, examples of which include methanol, ethanol, isopropanol, etc.
Examples include butanol. Furthermore, particularly favorable results can be obtained by using a mixed solvent containing an organic solvent that is miscible with the lower aliphatic alcohol. The organic solvent that is miscible with the lower aliphatic alcohol may be either a hydrophilic organic solvent or a hydrophobic organic solvent. Specific examples of the hydrophilic organic solvent include acetonitrile, tetrahydrofuran, dimethylformamide, etc., and hydrophobic organic solvents. Specifically, carbon tetrachloride, chloroform, methylene chloride,
Examples include halogenated hydrocarbons such as dichloroethane, aliphatic or alicyclic hydrocarbons such as pentane, hexane, and cyclohexane. The mixing ratio of the solvent is usually 9/1 to 9/1 as the volume ratio of lower aliphatic alcohol/the above organic solvent.
It can be used within a range of 1/9.

More favorable results can also be obtained by adding a small amount of acid to the solvent system. A mineral acid, an organic acid, etc. can be used as the acid, and is used as a proton source in cathodic reduction. The amount added is not particularly limited.

The amount of the solvent used is not particularly limited, and is appropriately determined depending on the reaction conditions and the like.

The concentration of 4,4'-diphenoquinones in the solvent is not particularly limited. However, from the viewpoint of reaction efficiency, a higher concentration is preferable.

Various salts can be used as supporting electrolytes in the present invention. The cation moiety of the above salt is, for example, sodium (Nal
, lithium (Li"), potassium (K'"); alkaline earth metal cations such as magnesium (Mg"), calcium (Ca"), barium (B a "); general formula (In the formula, R5, R6, R7 and R8 are hydrogen atoms or alkyl groups.) Examples of the anion moiety of the salt include substituted or unsubstituted ammonium ions represented by:
perchloric acid ((do4-), fluoroboric acid (BF,
-), I)-) Luenesulfonic acid (CH3C6H4SO
Examples include sulfonic acids such as 3-) and anions such as sulfuric acid (so4''-).

The concentration of the supporting electrolyte is usually in the range of 0.01 to 5.0M, preferably about 0.05 to 1.0M.

The reaction temperature should normally be 10 Q'C or less, preferably in the range of -20'C to 50°C.

The current density of the electrolytic reduction reaction in the present invention is usually 0.0
It can be selected in the range of 1 to 50 A/dnf, but preferably 0
．． 05 to 2 OA/dbo.

The amount of electricity to be applied is 2 to 10 fara days, preferably 2 to 1 mole of 4,4'-diphenoquinone as a reaction raw material.
~5 Faradays.

The electrolytic reaction in the present invention may be carried out in air or in an inert gas atmosphere, and is not particularly limited.

Further, the reaction time is appropriately selected depending on the substrate concentration, current density, and other reaction conditions.

〔Example〕

The present invention will be described in more detail with reference to Examples below, but the present invention is not limited by the Examples unless it exceeds the gist thereof.

Example 1 A 3°5.
3',5'-tetra-mo-butyldiphenoquinone (hereinafter referred to as TBDPQ) 204mg (0.5mmol
), 324 mg of lithium perchlorate (3,0 mmo I
), 7 ml of methanol, and 3 mρ of methylene chloride were added.

A platinum plate electrode (2 cm x 3 cm) was attached, cooled on ice, and constant current electrolysis was performed under conditions of a current density of 0.2 A/drrf. 5 for TBDPQI mole of reaction raw material
．． An electrolytic reduction reaction was carried out by applying electricity of 2 faradays. Analysis of the reaction product showed a raw material conversion rate of 56.8.
%, the selectivity of 44'-dihydroxy-3,5,3',5'-tetra-t-butylbiphenyl (hereinafter referred to as TBBP) was 100%.

Example 2 324 mg of lithium perchlorate was placed in each of the anode chamber and cathode chamber of an H-type diaphragm electrolytic cell using a cation exchange membrane as a diaphragm.
(3.0 mmol), 1 mQ of methanol, and 3 mfl of methylene chloride were added. TBDPQ2 in the cathode chamber
06 mg (0,5 mmo I) and concentrated sulfuric acid 0.03
ml was added. Platinum plate electrodes (2C
IIIX2cm), cooled on ice, and current density 0.1
Constant current electrolysis was performed under A/d port conditions. T of reaction raw material
After applying an electric current of 2.3 far days per mole of BDPQ and analyzing the reaction product, it was found that the raw material conversion rate was 92.
2%, and the selectivity of TBBP was 100%.

Example 3 An electrolytic reduction reaction was carried out in the same manner as in Example 2 except that a mixed solvent of methanol/methylene chloride (5Id15d) was used instead of methanol and methylene chloride. Raw material conversion rate 99.8%, TBBP selectivity 10
It was 0%.

〔Effect of the invention〕

According to the method of the present invention, 4,4'-diphenoquinones, which can be easily synthesized from alkylphenols, are used as starting materials, and 4,4'-dihydroxybiphenyls, which are important as organic synthesis intermediates, are produced under mild conditions by electrolytic reduction. Good purity,
It can be produced efficiently with high yield.

Therefore, the industrial utility of the present invention is extremely high.

Claims (1)

[Claims] (1) General formula (I): ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(I) (In the formula, R_1, R_2, R_3 and R_4 represent an alkyl group having 1 to 12 carbon atoms or a hydrogen atom, and are mutually exclusive. 4,4'-diphenoquinones represented by After electrolytic reduction, the general formula (II): ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(II) (In the formula, R_1, R_2, R_3 and R_4 have the same meanings as above) 4,4'-dihydroxybiphenyl 1. A method for producing 4,4'-dihydroxybiphenyls, which is characterized by obtaining 4,4'-dihydroxybiphenyls.