JPH0375391A - Production of m-cyanobenzyl alcohol - Google Patents

Abstract

PURPOSE:To enhance the yield of m-cyanobenzyl alcohol by electrolytically reducing m-cyanobenzoic acid or m-cyanobenzoic ester with a metallic material having high hydrogen overvoltage. CONSTITUTION:m-Cyanobenzoic acid or m-cyanobenzoic ester is electrolytically reduced in the presence of water and/or a water soluble org. solvent and/or quat. ammonium salt at pH<=4 with a metallic material having high hydrogen overvoltage as the cathode. The metallic material is made of Zn, Pb, Cd, Hg or an alloy contg. such metals. m-Cyanobenzyl alcohol is produced by an industrially superior method.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing m-cyanobenzyl alcohol. More specifically, the present invention relates to a method for producing -cyanobenzyl alcohol by electrolytically reducing m-cyanobenzoic acid or an ester of m-cyanobenzoic acid.

(2)-Cyanobenzyl alcohol is a compound useful as a raw material for various medicines and agricultural chemicals, but at present it has not been commercially supplied by inexpensive manufacturing methods.

[Prior art and problems to be solved by the invention] As a method for synthesizing tocyanobenzyl alcohol, aminobenzoic acid is reduced to amalgam to form doaminobenzyl alcohol, and then the amino group is diazotized and cyanated. A method of treating with copper and removing tocyanobenzyl alcohol (Be
r (38) 2063 (1905)] has been reported, but the number of steps is long and diazotization and cyanation are complicated, making it impractical.

Tocyanobenzoic acid is relatively easy to produce and seems to be suitable as a raw material for the synthesis of cyanobenzyl alcohol. The method for dissolving benzyl alcohol is to use a hydride reagent such as LiA I Ha,
Alternatively, under normal carboxylic acid reduction conditions such as hydrogenation, the cyano group is similarly reduced, so there is a problem in selectivity to dilute cyanobenzyl alcohol.

As a method to increase the selectivity and yield to tocyanobenzyl alcohol, there is a method in which 1''-cyanobenzoic acid is reacted with ethyl chloroacetate and then reduced with NaBHn (Japanese Patent Laid-Open No. 60-9794).
6).

2, ethyl ester of m1-cyanobenzoic acid is converted to Ca(B
Hn) Method of reduction with z [J, Org, Chem, 47
(24) 4702 (1982)).

have been proposed, but both have low yields of 63% and 70%, respectively, even though they use stoichiometric amounts of expensive reducing agents.
This was insufficient as an industrial manufacturing method.

That is, although cyanobenzoic acid is an excellent starting material for cyanobenzyl alcohol synthesis,
At present, an inexpensive and selective reduction technology to cyanobenzyl alcohol has not been developed.

The purpose of the present invention is to provide a simple, inexpensive, and high-yield method for producing m-cyanobenzyl alcohol, which selectively reduces only the carboxylic acid or ester while leaving the cyano group of cyanobenzoic acid or its ester. That's true.

[Means to solve the problem]

The present inventors have conducted extensive studies on a method for reducing m-cyanobenzoic acid that overcomes the drawbacks of the prior art as described above, and have found that m-cyanobenzyl alcohol can be reduced by electrolytic reduction of tocyanobenzoic acid or its ester. It was discovered that it can be obtained selectively.

That is, the present invention maintains m-cyanobenzoic acid or its ester at pH 4 or less in the presence of water and/or a water-soluble organic solvent and/or a quaternary ammonium salt, and uses a metal material with a high hydrogen overvoltage as a cathode. This is a method for producing m-cyanobenzyl alcohol, which is characterized by carrying out electrolytic reduction.

The present invention will be explained in detail below.

The method of the present invention is usually carried out using an electrolytic cell in which the cathode and anode compartments are separated by a cation exchange membrane or a glass diaphragm. By using a low anode material, the reaction can also be carried out without a diaphragm.

In the method of the present invention, the pH of the electrolyte is an important factor. Since the reaction progresses slowly under alkaline conditions, it is preferable to carry out electrolysis under acidic conditions, and a pH of 4 or less is suitable.

The means for keeping the solution acidic is not particularly limited as long as it is an acidic substance that does not participate in electrolytic reactions, but for boat fishing it is preferable to add mineral acids or sulfonic acids to the water solvent, especially sulfuric acid is inexpensive and Moreover, it is not corrosive to reactive materials and is easy to use.

In addition, in the method of the present invention, m-cyanobenzoic acid or its ester as a raw material has low solubility in an acidic aqueous solution, and when a raw material that greatly exceeds the solubility is added to increase the volumetric efficiency of the reaction, insoluble raw materials may be added. It also causes a decrease in the reaction activity of the cathode. Therefore, in order to increase the solubility, it is also a preferable method to add a quaternary ammonium salt, a water-soluble organic solvent, or both to the electrolytic reaction solution.

The quaternary ammonium salt is represented by the following general formula (1).

(In the formula, Rls Rz, R1, R4 are lower 7)L/kyl group, X is p-) represents any acid group of luenesulfonic acid, sulfuric acid, hydrochloric acid or hydrobromic acid) Add up to 60% by weight based on the acidic aqueous solution used. Even if more than that is added, no particular improvement in solubility is observed.

The water-soluble organic solvent is not particularly limited as long as it is a solvent that mixes uniformly with water and increases the solubility of tocyanobenzoic acid, but examples include acetonitrile, N,N''-dimethylyydacyridinone, N,N-dimethylformamide,
Aprotic polar solvents such as N-methyl-2-pyrrolidone and sulfolane; alcohols such as methanol, ethanol, propanol, and butanol; and glycols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, and polyethylene glycol. , or their monomethyl ether, monoethyl ether, monopropyl ether, monobutyl ether, etc.

These organic solvents are added in an amount of at most 10 times the weight of the acidic aqueous solution used. Even if more than that is added, no particular improvement in solubility is observed.

The concentration of m-cyanobenzoic acid in the electrolyte is usually 0°5~
It is in the range of 40% by weight. If it is less than 0.5%, the volumetric efficiency of the reaction is poor, and if it is more than 40%, it will not dissolve sufficiently and the reaction efficiency will decrease.

The method of adding raw materials varies depending on the concentration of cyanobenzoic acid or its ester added and the solubility of tocyanobenzoic acid or its ester in the reaction solvent used, but the acidity of tocyanobenzoic acid or its ester Because of its low solubility in aqueous solutions, it is preferable to charge it in portions as the reaction progresses rather than adding it all at once at the beginning of the reaction.

In addition, in the case of the diaphragm method in which this reaction is carried out in an electrolytic cell with positive and cathode compartments separated by a diaphragm, the raw materials tocyanobenzoic acid or its ester, quaternary ammonium salt, water-soluble organic solvent, etc. are placed on the cathode side. On the anode side, although not particularly limited, usually only an aqueous sulfuric acid solution is used.

As the diaphragm, glass diaphragm, asbestos, ion exchange membrane, etc. are used.

In the method of the present invention, the electrolytic reduction reaction
It is carried out in the temperature range of C. If the temperature is less than 20'C, the reaction will be slow, and if it exceeds 100°C, water and the added organic solvent will evaporate, making the reaction complicated.

In addition, among the electrodes, the cathode material in particular is the reduction potential of the side chain carbonyl group of tocyanobenzoic acid (1,62V vs Hg/Hg
Metals having hydrogen overpotentials more base than zSOa ), specifically zinc, lead, cadmium, and mercury, or alloys containing them are also used.

When a cathode material having a low hydrogen overvoltage such as nickel, platinum, or iron is used, reduction of carboxylic acid does not proceed, and reduction of cyano groups takes priority.

Further, in the case of the diaphragm method, the anode may be made of any ordinary electrode material and is not particularly limited.

The current density for the reaction is usually 1 to 30 A/drrf, and if it is less than IA/drrf, it takes time to supply a predetermined amount of electricity, resulting in a decrease in volumetric efficiency. Also 30 A/
The current efficiency decreases above d nf.

Theoretically, this reaction is a 4-electron reduction, and 4 Fr/mol
The reaction is supposed to end when electricity is applied, but in reality, hydrogen generation occurs as a side reaction due to electrolysis of water, so an amount of electricity of 10 to 40 Fr/mol is required to complete the reaction.

The anode material for the non-diaphragm method is a metal oxide that is stable in an acidic aqueous solution, and its oxygen overvoltage is 0.1 A/d- to 100 A/dw'' at a working current density of 0.1 A/d- to 100 A/dw'', and the oxygen overvoltage is based on the mercury sulfate electrode standard. +1.IV (measured at 25°C in a 15% by weight sulfuric acid aqueous solution, +1.7 in terms of standard hydrogen electrode)
V) The following oxides may be used, and the oxides may be coated on the surface of the metal substrate.

In this case, the oxides include ruthenium oxide of Group 8 platinum group, rhodium oxide, palladium oxide, osmium oxide,
Examples include iridium oxide, platinum oxide, tin oxide, tantalum oxide, cobalt oxide, and mixtures thereof.

Industrially, DSE (Dime
sionally 5table Electrod
e) is desirable.

[Effect]

To date, no inexpensive industrial production method for tocyanobenzyl alcohol has been established, and Akebono's cyanobenzyl alcohol can be produced by selectively reducing only tocyanobenzoic acid, which is considered to be an advantageous raw material, or the carboxylic acid of its ester. Although the production method did not give a satisfactory yield of the target product even if a stoichiometric amount of an expensive reducing agent was used, by using an electrolytic method, the target product can be obtained easily and in high yield.

That is, the present invention provides an industrially excellent method for producing -cyanobenzyl alcohol.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited to these.

In addition, % means weight %.

Example 1 An H-type electrolytic cell in which both electrode chambers have a capacity of 401 d and an anode and a cathode are separated by a glass diaphragm is used, and 15 g of 15% sulfuric acid water is charged into each electrode chamber.

Furthermore, 0.15 g (1°02+wwol) of tocyanobenzoic acid is added to the cathode chamber. Effective area for cathode 5.
5 CD lead plate, platinum plate with the same area for the anode! Constant current electrolysis at 0.4 A was carried out at 70° C. in the 9 reaction sections used as electrodes, and the reaction was stopped when 12 Fr/mo1 current was applied.

After the electrolysis was completed, the catholyte was analyzed by liquid chromatography, and the conversion rate of m-cyanobenzoic acid was 98.0%, and the yield of tocyanobenzyl alcohol was 85.5%.

Example 2 Using the same electrolytic cell as in Example 1, 15 g of 15% sulfuric acid water was added to the anode chamber, and 15 g of diethylene glycol:30% sulfuric acid water (1:1.) mixed solvent was added to the cathode chamber. A constant DC current of IA was applied at 70° C. using the electrode.

Raw material m-cyanobenzoic acid (1.5g, 10.2ms
The reaction was stopped when a total of 12 Fr/mol (12 Fr/mol) of current was applied) to the cathode chamber in portions.

As a result of analysis by liquid chromatography, the conversion rate of cyanobenzoic acid was 97.3%, and the yield of tocyanobenzyl alcohol was 84.9%.

Example 3 Using the same electrolytic cell as in Example 1, 15 g of 15% sulfuric acid water was placed in the anode chamber, 15 g of boric acid-ammonium hydroxide buffer (p)14) was placed in the cathode chamber, and 0.45 g of sodium sulfate was charged as a supporting electrolyte. In addition, the catholyte contains 0.15 g of m-cyanobenzoic acid methyl ester (0.93 mmo
l) was added.

Using the same electrode as in Example 1, 0.4 A constant current electrolysis was performed at room temperature, and a current of 30 Fr/mo1 was applied.

As a result of analysis by liquid chromatography, the conversion rate of m-cyanobenzoic acid methyl ester was 62.5%, and the yield of tocyanobenzyl alcohol was 55.3%.

Example 4 1 part of 20% sulfuric acid water was added to a cylindrical single electrolytic cell with a capacity of 100 m.
0g 1 ethanol 10g, tetraethylammonium 1
1-) Luenesulfonate Ig and tocyanobenzoic acid 1.
5 g (lo, 2 mol) was charged.

A lead plate with an effective area of 5.5 cj was used as a cathode, and a titanium plate coated with iridium oxide on the surface of the same area was used as an anode (oxygen overvoltage: +0, 95 V vs. HgzSOa). Perform 0.5A DC constant current electrolysis at room temperature at 15F.
The reaction was stopped when r/mo1 current was applied.

When analyzed by liquid chromatography in the same manner as in Example 1, the conversion rate of tocyanobenzoic acid was 97.9%.
The yield of tocyanobenzyl alcohol was 82.9%.

Comparative Example 1 Using the same electrolytic cell as in Example 1, 15 g of 15% sulfuric acid water was placed in the anode chamber, 15 g of disodium hydrogen phosphate-sodium hydroxide buffer (pH 10) was placed in the cathode chamber, and 0.45 g of sodium sulfate was used as the supporting electrolyte. Furthermore, 0.15 g (1.0 mmol) of tocyanobenzoic acid was added to the catholyte.

Using the same electrode as in Example 1, constant current electrolysis of 0.4 A was carried out at room temperature, and a current of 30 Fr/s+o1 was applied.

As a result of analysis by liquid chromatography, the conversion rate of -cyanobenzoic acid was 8.2%, and the yield of -cyanobenzyl alcohol was 5.8%.

Comparative Example 2 Using the same electrolytic cell as in Example 1, 15 g of 5% sodium hydroxide aqueous solution was charged into the anode and cathode chambers, and 0.15 (1,05 g) of tocyanobenzoic acid was added to the catholyte.
nol) was added. Using the same electrode as in Example 1, constant current electrolysis at 0.4 A was performed at room temperature at 30Fr/mo.
1 power was applied.

As a result of analysis by liquid chromatography, the conversion rate of cyanobenzoic acid and the yield of m-cyanobenzyl alcohol were less than 1%.

C Effect of the invention] As can be seen from the examples and comparative examples, when the pH of the electrolytic solution during the electrolytic reduction reaction is not on the alkaline side but on the acidic side of pH 4 or less, the yield of snoring cyanobenzyl alcohol is good. I understand.

Claims (1)

[Claims] 1. m-cyanobenzoic acid or an ester of m-cyanobenzoic acid is hydrogenated by maintaining it at pH 4 or below in the presence of water and/or a water-soluble organic solvent and/or a quaternary ammonium salt. A method for producing m-cyanobenzyl alcohol, which comprises carrying out electrolytic reduction using a metal material with high overvoltage as a cathode. 2. The method according to claim 1, wherein the metal material having a high hydrogen overvoltage is zinc, lead, cadmium, mercury, or an alloy containing these metals.