SU210768A1 - - Google Patents

Description

METHOD OF OBTAINING DESIGNED a-OXYLIC ACIDS

A known method for producing disubstituted a-hydroxy acids by oxidation of 2,2,5,5-tetra-substituted 3-oxotetrahydrofurans with permanganate or nitric acid, followed by cleavage of the resulting esters.

The proposed method consists in that 2,2,5,5-tetrasubstituted 3-oxotetrahydrofurans are oxylated by alkyl nitrite at a temperature of 45-50 ° C, treated with at least 85 wt. % sulfuric acid, followed by neutralization of the excess of this acid with a solution of alkali and hydrolyzing the resulting mixture of a-hydroxy acid and its amide (and if sulfuric acid was treated in the presence of alcohol, then ether) with 25% hydrochloric acid. The new method allows to increase the yield of the target product.

Example 1. 6.0 ml of concentrated hydrochloric acid and 31.0 g (0.2 mol) of 2,5-dimethyl-2, 5-diethyl-3-oxotetragiDrofuran are introduced into a 250 ml four-necked flask equipped with a stirrer and a cooler. , a thermometer and a dropping funnel. The mixture is heated to. At this temperature, 25.8 g (0.22 mol} of amyl nitrite) are added dropwise. The reaction is exothermic, the temperature is maintained at 45-50 ° C by water cooling.

crystallization of the product of oxime. After adding the amyl nitrite residue, the mixture is stirred until the temperature — in the absence of external cooling — decreases to room temperature. The mixture is then evaporated at room temperature under a water-jet vacuum. Proximate oximes are obtained with a yield of 85 ° / o raw. This product is treated with 50 g of 96% sulfuric acid at a temperature of about minus 2 ° C with intensive external cooling and stirring, and 0.0585 mol (10 g) of the o-hydroxy 2,2,5,5-tetramethyl product is added in portions. -Z-oxotetrahydrofuran. An exothermic reaction starts immediately. Due to a minor adverse reaction, some HCN is formed. After a few minutes, the reaction is over, as evidenced by the lightening of the yellow color, and the mixture becomes colorless. When cooled, sulfuric acid is neutralized with a precisely calculated equimolar amount of caustic alkali (for example, 35 ° / about NaOH).

A mixture of 2-hydroxy-2-methyl butyric acid and its amide is isolated from the reaction mixture in a yield of 80%. C. The mixture is converted to 2-hydroxy-2-methyl butyric acid by hydrolysis with 200 liters / 25% hydrochloric acid. After recrystallization from gasoline, the acid melts at 72 ° C.

Example 2. 28.4 g (0.2 mol 2,2,5,5-tetramethyl-3-oxotetrahydrofuran in a mixture with ml of concentrated hydrochloric acid are heated to 40 ° C and then 25.8 g are added dropwise to the mixture (0.22 mol of amyl nitrite. The temperature is maintained at 45-50 ° C by cooling in a water bath. After the addition of amyl nitrite, the mixture is stirred until the temperature drops to room temperature without external cooling. Then 30 ml of gasoline is poured in. The oxime product is sucked off, three times washed with 15 ml of gasoline and dried B paraffin vacuum desiccator .You get 22.4 g (65.4 e / o from theory) about a-oximation of 2,2,5,5-tetramethyl-3-oxotetrahydrofuran with a melting point of 127 ° C. Nitrogen content, o / o: calculated 8.18, found 7.98.

In 63 3 98% sulfuric acid with a temperature of about -2 ° C with intensive external cooling and stirring, 9.2 g (0.2 mol) of pure ethyl alcohol are added in portions and then also 10 g (0, 0585 mol of a-oxime product 2,2,5,5-tetramethyl-3-oxotetrahydrofuran. After a few minutes, the reaction is complete, as indicated by the yellow color, and the mixture becomes colorless. The sulfuric acid reacted is reacted with a calculated amount of caustic alkali at cooling. The ethyl ether is separated from the reaction mixture. alpha hydroxyisobutyric acid, alpha hydroxyisobutyric acid and a small amount of its amide with a total yield of 750/0 (from theory). The proportion of ethyl ester of alpha hydroxyisobutyric acid accounts for about 80E / 0 total output. ether 148 ° C.

Example 3. The experiment was carried out in the same manner as in Example 1. The product of a-oximetization of 2,5-dimethyl-2,5-diphenyl-3-oxotetrahydrofuran is obtained. A total of 36% of the theory (based on the product of oxime) of atrolactic acid in the form of a hemihydrate (crystallized with half of the water molecule); after recrystallization from water, the hemihydrate melts at 66.5 ° C.

Example 4. Analogously to Example 1, a-oxime product of 2,2,5,5-tetra-n-propyl-3-oxotetrahydrofuraa is obtained. The yield of a-oxide-n-propyl acetic acid, 420/0 (from theory), after recrystallization from hot water, the needles are isolated, which melt at.

Subject invention

1. A method of obtaining disubstituted a-hydroxy acids from 2,2,5,5-tetrasubstituted 3-oxotetrahydrofurans, characterized in that, in order to increase the yield of the target product, the raw material is reacted with alkyl nitrite at a temperature of 45-50 ° C, followed by processing at least 85 wt. about / about sulfuric acid at a temperature of minus 5 - plus 70 ° С, neutralization of excess sulfuric acid with a solution of alkali and hydrolysis of the resulting mixture of a-hydroxy acid and its amide 250 / o-hydrochloric acid.

2. Method according to c. 1, characterized in that, in order to obtain an ester as an intermediate, the treatment with sulfuric acid is carried out in the presence of alcohol.