Process for the manufacture of alkyl pyruvates

DETAILED DESCRIPTION OF THE INVENTION The following examples illustrate the invention without in any way limiting its scope.
EXAMPLE 1 472 g (4 moles) of ethyl lactate, 64 g (0.
4 mole) of bromine is dissolved at room temperature in 2660 g of dichloromethane in a 4 liter three-necked glass flask equipped with a thermometer and a mechanical stirring system and irradiated with a 200 Watt incandescent lamp.
272 g of 50% by weight aqueous hydrogen peroxide (4 moles) was then introduced into the stirred irradiated solution over a period of 90 minutes.
The temperature of the reaction medium was kept to 25.
degree.
C.
by light external cooling.
The reaction medium was left, maintaining the temperature of 25.
degree.
C.
, the irradiation and the stirring.
After three hours, analysis of a sample by vapour phase chromatography showed that the ethyl lactate had completely disappeared.
The reaction medium was then neutralised under agitation with sodium bicarbonate, then decanted.
After washing with an aqueous solution of 50.
4 g of sodium sulphite in 500 g of water, the organic phase was concentrated and the residual oil distilled under 80 mbar pressure.
372 g (3.
2 mole) ethyl pyruvate was isolated, i.
e.
a yield of 80.
2% of theory calculated with respect to ethyl lactate.
EXAMPLE 2 The process of example 1 was repeated using methyl lactate.
A 72% yield of methyl pyruvate was isolated.
EXAMPLE 3 The process of example 1 was repeated using butyl lactate.
An 88% yield of pure butyle pyruvate was isolated.
EXAMPLE 4 The process of example 1 was repeated in daylight, in the absence of the illumination provided by the incandescent lamp.
Complete disappearance of the ethyl lactate took six hours following addition of the hydrogen peroxide.
After treatment, a yield of 80% of theory of ethyl pyruvate was isolated.
EXAMPLE 5 The process of example 1 was repeated in complete darkness and the reaction medium left for 10 hours at 25.
degree.
C.
in darkness and under agitation.
After treatment, a yield of 80% of theory of ethyl pyruvate was isolated