CS268279B1 - Method of 5-hydroxy-2-pentanone preparation - Google Patents

Abstract

Mowing refers to the method of preparation 5-hydroxy-2-pentanone of the formula Alkaline re-etherification of 4-oxopentylalkanoates of Formula II where R-H or alkyl having the number of carbons C to C, by treatment with an alcoholic solution methoxide or ethoxide or hydroxide or sodium carbonate or potassium.

Description

The invention relates to a process for the preparation of 5-hydroxy-2-pentanone of formula I.

5-Hydroxy-2-pentanone of formula I is an important intermediate in organic synthesis. It is the starting material for the production of drugs, vitamin B 1 and azo initiators used for the synthesis of teleohelical polymers.

The hydrolysis or alcoholysis of 4-oxopentyl acetate to the hydroxypentanone of formula I is carried out in alcohol solution catalyzed by hydrochloric acid, sulfuric acid or acidic ion exchangers (Grigoriev AA, Kayman EA, Bobrov®, P., Danko TN, Pinkhaaik EV: Khim. Prom. (Moscow) 8, 45β (1981). The reaction mixtures after hydrolysis must be neutralized with bases and the hydroxypentanone of the formula I isolated by distillation. Under these conditions, however, the hydroxypentanone of the formula I is partially converted to the 2-methyl-2- (4-oxopentyloxy) -tetrahydrofuran of the formula III.

The process for the preparation of hydroxypentanone of the formula I according to the invention overcomes these drawbacks. Its essence lies in the fact that the 4-oxopentylalkanoate of the general formula II, in which RH or alkyl having a number of carbons up to C14, is treated with an alcoholic solution of methoxide or ethoxide or sodium or potassium hydroxide or carbonate at temperatures of 10 to 40 ° C, preferably then at room temperature. The reaction is carried out by dissolving the 4-oxopentylalkanoate of the formula II in a methanolic or ethanolic solution of methoxide or sodium or potassium methoxide or hydroxide and allowing the reaction mixture to stand with occasional stirring at 10-40 ° C, preferably at room temperature. The progress of the reaction can be monitored by thin layer chromatography of the reaction mixture. After complete conversion of the 4-oxopentylalkanoate of the formula II to the hydroxypentanone of the formula I, the alkali metal methoxide or hydroxide is neutralized with carbon dioxide, the methanol is evaporated off under reduced pressure, the precipitated alkali metal carbonate is filtered off and washed with ether. After evaporation of the ether, 5-hydroxy-2-pentanone of formula I is obtained, which is sufficiently pure for further use.

The effect of the process according to the invention is that the alkaline reesterification of the 4-oxo pentylalkanoates of the formula II takes place quantitatively under very mild reaction conditions. The advantages of the process are high yields of practically pure 5-hydroxy-2-pentanone of formula I, mild reaction conditions and easy isolation of the product.

The process according to the invention is further described by means of several exemplary embodiments.

Example 1

4-Oxopentyl acetate (II, R-CH 2 Cl 2, 21.6 g, 0.15 mol) was dissolved in methanol (150 mL) containing sodium methoxide (0.2 g). The resulting homogeneous solution was allowed to stand for 5 hours at room temperature. Then, the reaction mixture was neutralized with the indicated carbon dioxide, the methanol was evaporated from the reaction mixture under reduced pressure, and the residue was extracted with ether. After evaporation of the ether, 4.7 g (96%) of chromatographically pure 5-hydroxy-2-pentanone were obtained, the structure of which was proved by NMR spectrum.

Example 2. A solution of 4-oxopentyl formate (II, R-Ηζ 13 · θ θ · ^{1 m} ° D ⁱⁿ methanol (100 ml) containing sodium methoxide (0.2 g) was allowed to stand at room temperature for 2 hours. During this time, complete conversion of the starting oxopentyl formate of formula II (RH), the reaction mixture was neutralized by the introduction of carbon dioxide, the methanol was evaporated under reduced pressure, the precipitated sodium carbonate was filtered off and the residue was extracted with ether to give 9.7 g (95%). ) in chromatographically pure 5-hydroxy-2-pentanone.

Example 3

The reaction beads containing 4-oxopentyl formate (II, R-Ηζ 10.0 g ', 0.77 mol), methanol (100 ml) and potassium carbonate (2.0 g) were stirred at 30-40 ° C for 10 hours. Then the methanol was evaporated in vacuo, the potassium carbonate was filtered off and the residue was extracted with ether. After distilling off the ether, 7.1 g (90.5%) of 5-hydroxy-2-pentanone were obtained.

Example 4

The reaction mixture containing 4-oxopentyl acetate (II, R-CH 2) *, 14.4 g (0.1 mol), ethanol (100 ml) and sodium ethoxide (0.2 g) was allowed to stand at room temperature under occasional stirring for 9 hours. Then, the reaction mixture was neutralized with carbon dioxide gas, the ethanol was evaporated from the reaction mixture under reduced pressure, the precipitated sodium carbonate was filtered off, and the residue was extracted with ether. After evaporation of the ether, 9.1 g (89.2%) of 5-hydroxy-2-pentanone were obtained.

Example 5

Sodium (0.1 g) was added to a mixture of methanol (50 ml) and ethanol (50 ml), and after reacting, 4-oxopentyl acetate (II, R-CH 2 ζ 12.1 g) was added to the solution. The reaction mixture was allowed to stand at room temperature for 8 hours. Then the reaction mixture was neutralized with carbon dioxide, methanol and ethanol were evaporated under reduced pressure, the precipitated sodium carbonate was filtered off and the residue was extracted with ether. After evaporation of the ether, 7.5 g of 5-hydroxy-2-pentanone were obtained.

Claims (1)

OBJECT OF THE INVENTION Process for the preparation of 5-hydroxy-2-pentanone of the formula I, characterized in that the 4-oxopentylalkanoate of the general formula II, in which R @ 1 or alkyl having carbon numbers C ₁ to C 4, is treated with an alcoholic solution of methoxide or ethoxide or hydroxide or sodium or potassium carbonate at temperatures of 10 to 40 ° C, preferably at room temperature.