JPS645114B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method for producing 2,5-dihydro-2,5-diacetoxyfuran.

2,5-dihydro-2,5-diacetoxyfuran is an important compound as an intermediate for synthesizing malealdehyde, 2-acetoxytetrahydrofuran, and the like. A method for producing 2,5-dihydro-2,5-diacetoxyfuran is, for example, a method in which furan is treated with lead tetraacetate (Acta Chem.
Scand., 6 , 535 (1952)), a method in which furan is first brominated and then acetoxylated (Acta
Chem. Scand., 4 , 1233 (1950)), but all of these methods have serious drawbacks and are unsuitable for production on an industrial scale. That is, the former method requires the use of lead tetraacetate, which causes pollution and is expensive, and therefore poses problems in terms of environmental hygiene and economy. In addition, the latter method requires a long process and requires the reaction to be carried out at an extremely low temperature of -60 to -50°C, making the reaction operation complicated and disadvantageous for industrial production. Also, a method of electrolytically oxidizing furan (J.Chem.Soc., 969
(1968)) is also known, but this method can only obtain the desired product with a yield of only about 12%, and is far from practical.

The purpose of the present invention is to produce the desired 2,5-dihydro-2,5-diacetoxyfuran in high yield by simple operations under mild conditions without the need for special reagents such as lead tetraacetate. The purpose is to provide a method for manufacturing.

That is, the present invention provides 2,5-dihydro-
Relates to a method for producing 2,5-diacetoxyfuran.

According to the method of the present invention, an extremely simple operation of electrolytically oxidizing furan at low temperature in the presence of acetic acid,
Under mild reaction conditions, the target compound can be obtained with a yield as high as 75% or more. In addition, the method of the invention completely eliminates the use of hazardous reagents such as lead tetraacetate.

In the present invention, it is essential that acetic acid be present in the reaction system. The amount of acetic acid used is not particularly limited, but is usually used in a large excess amount relative to furan. This acetic acid also acts as a reaction solvent. In the present invention, a mixed solvent of acetic acid and another suitable solvent can also be used as a reaction solvent. As such a solvent, a wide variety of known solvents can be used as long as they have a low freezing point, are inert during electrolytic oxidation, and are compatible with acetic acid and furan, such as acetonitrile,
Examples include ethyl acetate and ether.

A normal supporting electrolyte can be used as the supporting electrolyte when performing electrolytic oxidation. for example,
Examples include common salt, potassium bromide, acetate, quaternary ammonium salt, mineral acid salt, organic acid salt, and organic sulfonate. Among these, it is preferable to use acetate. The reaction temperature of the electrolytic oxidation reaction is preferably lower, but is limited by the freezing point of acetic acid and other solvents. Preferably in the range of 0 to 30°C,
Particularly preferably, the temperature is in the range of 0 to 20°C. At a low reaction temperature, side reactions are suppressed and the desired product is stable, but at the same time, the dissipation of the raw material furan can be suppressed. In the electrolytic reaction, ordinary electrodes are used. For example, platinum, carbon, iron, lead,
Stainless steel, platinum coated material, titanium, etc. can be mentioned. A diaphragm may be used, but no diaphragm is sufficient. The obtained 2,5-dihydro-
2,5-Diacetoxyfuran is a mixture of cis and trans forms. Normally, the raw material furan is placed in a reaction vessel together with a solvent to carry out the reaction.
It is also promising to carry out the reaction while dropping raw material furan because it suppresses the dissipation of unreacted furan.

Examples will be described below.

Example 1 2 g of furan is dissolved in a mixed solvent of 40 ml of acetic acid and 10 ml of acetonitrile, and 2 g of sodium acetate is added.
A platinum electrode as an anode and a carbon electrode as a cathode are charged, and the temperature is maintained at 5 to 7°C to carry out an electrolytic reaction. After the reaction is complete, the reaction solution is poured into water and extracted three times with methylene chloride. The extracts are combined and dried over anhydrous magnesium sulfate. Methylene chloride is distilled off and the residue is distilled to obtain 2,5-dihydro-2,5-diacetoxyfuran. Yield 87% Boiling point 99-105℃/1.8mmHg.

Example 2 2 g of furan is dissolved in 40 ml of acetic acid and subjected to the same reaction treatment as in Example 1 while maintaining the temperature at 17 to 19°C to obtain 2,5-dihydro-2,5-diacetoxyfuran. Yield 75% Boiling point 99-104℃/1.7mmHg.

Example 3 2 g of sodium acetate was added to a mixed solvent of 40 ml of acetic acid and 10 ml of acetonitrile, a platinum electrode was placed as an anode, and a carbon electrode was placed as a cathode. drip. When the post-reaction treatment is carried out in the same manner as in Example 1, the target product 2,5-dihydro-2,5-diacetoxyfuran is obtained. Yield 83% Boiling point 100-105℃/2mmHg.

Claims (1)

[Claims] 1. A method for producing 2,5-dihydro-2,5-diacetoxyfuran, which comprises electrolytically oxidizing furan at a low temperature in the presence of acetic acid. 2. The method according to claim 1, wherein the electrolytic oxidation is carried out at a temperature of 20 to 30°C. 3. The method according to claim 1 or 2, which uses a mixed solvent containing acetic acid.