JPH0673584A - Production of hydroxypivalic ester - Google Patents

Abstract

PURPOSE:To efficiently synthesize a hydroxypivalic ester by combining a carbonaceous anode and a supporting electrolyte of a neutral halate to bring about an electrolytic reaction between hydroxypivalaldehyde and alcohol. CONSTITUTION:A hydroxypivalic ester is synthesized from hydroxypivalaldehyde and alcohol by an electrode reaction. In this case, an inexpensive carbonaceous anode (carbon anode) and a neutral halate are used instead of the platinum anode and an alkali-metal alcoholate. Consequently, the wear resistance of electrode is improved in the electrode reaction, and a hydroxypivalic ester is efficiently produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for electrolytically producing hydroxypivalic acid ester from hydroxypivalaldehyde and alcohol. Hydroxypivalic acid ester is industrially useful as an intermediate raw material for synthesizing various compounds such as pharmaceuticals, agricultural chemicals and poly-shill.

[0002]

2. Description of the Related Art A method for synthesizing a carboxylic acid ester from an aldehyde and an alcohol by an electrolytic reaction is disclosed in JP-B-43.
-14683, and J. Org. Chem., Vol.53.
(1988), p218. In these methods, an alkali metal alcoholate is used as the electrolyte.
The use of alkali metal alcoholates is an unstable substance that decomposes in water, air, etc. and is difficult to handle. However, there are drawbacks such as inducing the side reaction of (3) and decreasing the yield of the target ester. In particular, in order to avoid the inconveniences described below, it is necessary to quickly decompose the alkali metal alcoholate by an operation such as neutralization after completion of electrolysis, which complicates the process and makes it impossible to recover and reuse the electrolyte. There are many points to be improved in the known method, such as further inconvenience in practical use. Further, in the electrolytic reaction in the known method, the use of a platinum electrode and the use of a halogenate electrolyte are common, but especially in the system of a platinum anode and a halogenate electrolyte, the consumption of the electrode due to electrolysis is extremely significant and the Is not industrially preferable in that not only the difficult electrolytic reaction becomes difficult, but also the expensive platinum electrode is consumed. Furthermore, when these known methods are applied to the synthesis of hydroxypivalic acid ester from hydroxypivalaldehyde and alcohol, the selectivity to hydroxypivalic acid ester cannot be said to be sufficient.

[0003]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned problems in the prior art and efficiently electrolytically produce hydroxypivalate ester from hydroxypivalaldehyde and alcohol under mild conditions in a single step. To provide a method.

[0004]

As a result of intensive studies to solve the above problems, the present inventor has found that an anode made of a carbon material (hereinafter referred to as a carbon positive electrode) without using a platinum anode and an alkali metal alcoholate. It was found that hydroxypivalic acid ester can be efficiently synthesized by electrolytically reacting hydroxypivalaldehyde with an alcohol in a system in which a supporting electrolyte of a neutral halogenate) is combined. The reaction of forming hydroxypivalic acid ester in the present invention can be represented by the following formula.

[0005]

[Chemical formula 1] HC (O) -C (CH ₃ ) ₂ -CH ₂ OH + ROH → RO-C (O) -C (C
_{H 3) 2 -CH 2 OH +} 2H + + 2 e - alcohol used in the present invention: is represented by the general formula ROH, R group represents an alkyl group, methyl examples, ethyl, n chromatography propyl, i over Propyl, 2-formyl-2-
Examples thereof include methyl-propyl and benzyl groups.

The carbon positive electrode used in the present invention may be any conductor made of carbon as used in ordinary electrode reactions, such as graphite, amorphous carbon or the like molded by various methods or Gurathy carbon. Etc. can be used. The shapes of these electrodes are not particularly limited. The solvent used in the present invention may be any solvent that can dissolve hydroxypivalaldehyde, alcohol and a supporting electrolyte, and examples thereof include acetonitrile and dimethylformamide. Hydroxypivalaldehyde and alcohol can be dissolved in these solvents, or hydroxypivalaldehyde can be dissolved in alcohol itself and used. When water is contained in the solvent, oxygen is generated by electrolysis and side reactions such as oxygen oxidation of aldehyde proceed, so it is desirable that the water content is as small as possible.

The supporting electrolyte used in the present invention is not particularly limited as long as it is a neutral halogenate and is soluble in an electrolytic solvent, and examples of the cation include the periodic table 1A.
Ions of group elements, quaternary alkylammonium cations, and the like, and examples of anions include chlorine ions, bromine ions, iodide ions, and the like, and a halide salt of a combination of these cations and a halogen anion can be used. Among the halogen ions, iodide ion is particularly effective for obtaining high selectivity to hydroxypivalate ester.

The electrolytic chamber used in the present invention may be of any type such as a diaphragm type and a diaphragmless type. When a diaphragm type electrolysis chamber is used, hydroxypivalaldehyde is dissolved only in the anolyte and electrolysis is performed. At this time, the cathode and the diaphragm are not particularly limited as long as they are used in a usual electrolytic reaction. When a diaphragmless electrolytic chamber is used, it is preferable to use an electrode having a low hydrogen overvoltage as the cathode, since the by-production of neopentyl glycol increases when an electrode having a high hydrogen overvoltage is used as the cathode. Examples include platinum, carbon, copper and the like. With respect to the shape and arrangement of the electrode pair, those used in ordinary electrolytic reactions can be used. In particular, the distance between the anode and the cathode is preferably as small as possible in order to improve current and voltage efficiency, and it is practical to use a capillary gap cell or the like.

The conditions such as electrolysis temperature, electrolysis pressure, and current density in the present invention are not particularly limited, but from a practical viewpoint, they are 0 to 80 ° C., 1 to 10 atmospheres, and 1 to 25, respectively.
It is preferably about A / dm ² . Further, the concentrations of hydroxypivalaldehyde, alcohol and supporting electrolyte in the electrolytic solvent are practically 10 g to 1.2 kg of hydroxypivalaldehyde and 10 g of alcohol per 1 kg of the solvent.
It is desirable that the amount is about 1.2 kg and the supporting electrolyte is about 1 to 200 g. When alcohol itself is used as the solvent, it is desirable that the amount of hydroxypivalaldehyde is 10 g to 1.2 kg and the supporting electrolyte is 1 to 150 g per kg of alcohol.

[0010]

INDUSTRIAL APPLICABILITY When an electrode reaction is applied and hydroxypivalic acid ester is synthesized from hydroxypivalaldehyde and alcohol, by using an inexpensive material such as a carbon positive electrode and a neutral halogenate, the electrolytic reaction process The wear resistance of the electrode was improved, and it became possible to efficiently produce hydroxypivalic acid ester.

[0011]

EXAMPLES The present invention will be specifically described below based on examples. However, the present invention is not limited to these examples. The following formula was used for the calculation of the following values.

Example 1 In a 250 ml separable flask, methanol 1
80 g, hydroxypivalaldehyde 20.4 g, and tetraethylammonium iodide 3.6 g were mixed. Two sets of electrode pairs were prepared in which two disc-shaped carbon electrodes having a geometric surface area of about 15 cm ² were fixed at an inter-electrode distance of 4 mm, and each set was unipolarly connected and immersed in the above-mentioned electrolytic solution. A current density of 6.8 A / dm ² and constant current control were applied. During the electrolysis reaction, the electrolysis voltage had a value of 12 to 15V. The stirring of the liquid was performed with a magnetic stirrer, and the temperature of the electrolytic solution was kept at about 10 to 20 ° C. by a water bath. The results are shown in Table 1.

Example 2 Using 1.5 g of sodium bromide as a supporting electrolyte, the apparatus of Example 1 and the electrode pair were used to carry out an electrolytic reaction under the same conditions. The results are shown in Table 1. Example 3 Using 2.0 g of sodium iodide as a supporting electrolyte, the apparatus of Example 1 and the electrode pair were used to perform an electrolytic reaction under the same conditions. The results are shown in Table 1. At this time, the amount of carbon electrode consumed by electrolysis was 0.9 g or less per unit weight of methyl hydroxypivalate produced.

Comparative Example 1 Using 1.5 g of sodium iodide and 0.7 g of sodium alcoholate as a supporting electrolyte, two platinum plates on a titanium plate were set as anodes, and the same method and apparatus as in Example 3 were used. Was used to carry out an electrolytic reaction under the same conditions. The results are shown in Table 1. The amount of the positive electrode consumed by electrolysis at this time was 18.7 g per unit weight of methyl hydroxypivalate produced.

[0015]

[Table 1]

Claims (1)

[Claims] 1. A hydroxypivalin characterized by using an anode made of a carbon material and a neutral halogenate salt as a supporting electrolyte in the one-step electrolytic synthesis of hydroxypivalate ester from hydroxypivalaldehyde and alcohol by an electrolytic reaction. Method for electrolytic production of acid ester.