Field of Invention
The present invention relates to the process of preparation of compounds having CHF2C(O) group .
Background of Invention
The U.S. Patent Application No. 2007/0191632 describes a process involving reduction of esters of chlorodifluoroacetic acid with zinc to produce difluoroacetic acid ester. It is further known that the esters of difluoroacetic acid can also be prepared by treating difluoroacetic acid with alcohol in presence of mineral acids such as sulphuric acid or phosphoric acid. The above process suffers from the drawback that the starting material chlorodifluoroacetic acid ester as well as difluoroacetic acid are readily not available. Furthermore, in case of reduction of chlorodifluoroacetic acid ester, the reaction generates zinc waste, thus making it industrially unfavorable.
The U.S. Patent No. 5,710,317 describes a process for the preparation of ethyl difluoroacetate by reacting difluoroacetic acid fluoride with ethanol at 50oC.
The present inventors have observed that carrying out the reaction of difluoroacetic acid fluoride with ethanol at 50oC makes the reaction unsafe due to the rapid and uncontrolled expulsion of HF gas. The present inventors observed that upon considerable lowering of reaction temperature, the same reaction proceeds to give favourable results without compromising the safety aspects, thus making it more industrially viable.

Summary of the Invention
The present invention provides a process for the preparation of a compound of Formula I, comprising;

Formula I
where R is selected from hydrogen and C1-C6 alkyl group

a) reacting a compound of Formula II with a compound of Formula III to obtain a reaction mixture, and

R-OH
Formula II Formula III

where X is selected from fluorine, chlorine, bromine and iodine; R is selected from hydrogen and C1-C6 alkyl group

b) isolating the compound of Formula I from the reaction mixture of step a), wherein step a) takes place at a temperature of not more than about 15oC.
Detailed Description of the Invention
In an aspect, the present invention provides a process for the preparation of a compound of Formula I, comprising;

Formula I
where R is selected from hydrogen and C1-C6 alkyl group
a) reacting a compound of Formula II with a compound of Formula III to obtain a reaction mixture, and
R-OH
Formula II Formula III

where X is selected from fluorine, chlorine, bromine and iodine; R is selected from hydrogen and C1-C6 alkyl group

b) isolating the compound of Formula I from the reaction mixture of step a), wherein step a) takes place at a temperature of not more than about 15oC.
The compound of Formula II may be prepared by any method known in the art, for example, known in the Indian Patent No. 262804 or U.S. Patent No. 5,710,317. The step a) is carried out at a temperature of about 8oC to about 15oC, for about 3 hours to about 7 hours.
The compound of Formula I is isolated by any of the methods in the art, for example, evaporation, distillation and layer separation or mixture thereof.
The compound of Formula I, as obtained by present invention, has purity of about 98% to about 99%. The compound of Formula I may be ethyl difluoroacetate.
The term ‘about’ refers to a variation of 10% on the higher and lower side of specified parameter.
While the present invention has been described in terms of its specific embodiments, certain modifications and equivalents will be apparent to those skilled in the art and are intended to be included within the scope of the present invention.

Example
Preparation of Ethyl difluoroacetate
The difluoroacetyl fluoride (65g) was passed through two towers containing 31g ethanol in each at a temperature of 8°C to 10°C at a rate of 16g to 25g per hour till the first tower depletes to level of 0.1% of ethanol by gas chromatography area. After completion of addition, the reaction mass in first tower was distilled to separate hydrogen fluoride and ethyl difluoroacetate. Now, the second tower becomes the first tower and new tower containing fresh ethanol was introduced and the process was continued to obtain the title compound.
Yield (%): 85
Purity (%):

CLAIMS:
We Claim:
1. A process for the preparation of a compound of Formula I, comprising:

Formula I
where R is selected from hydrogen and C1-C6 alkyl group
a) reacting a compound of Formula II with a compound of Formula III to obtain a reaction mixture, and
R-OH
Formula II Formula III
where X is selected from fluorine, chlorine, bromine and iodine; R is selected
from hydrogen and C1-C6 alkyl group

b) isolating the compound of Formula I from the reaction mixture of step a), wherein step a) takes place at a temperature of not more than about 15oC.

2. The process as claimed in claim 1, wherein the step a) is carried out at a temperature in the range of 8oC to 15oC.

3. The process as claimed in claim 1, wherein the step a) is carried out for a time period in the range of 3 hours to about 7 hours.

4. The process as claimed in claim 1, wherein the isolation of compound of Formula I is carried out by evaporation, distillation and layer separation or mixture thereof.

5. The compound of Formula I, as obtained from process as claimed in claim 1, having purity of about 98% to about 99%.