DESC:“PROCESS FOR THE PREPARATION OF PURE HALOACETAMIDES”

Field of the Invention
The present invention relates to the process for the preparation of pure haloacetamide of Formula I.
Background of the Invention
The haloacetamide of Formula I is an important intermediate and building block for the preparation of various agrochemical and pharmaceutical compounds.

Formula I
The J. Org. Chem., 24, 1959, 1256-1259 describes a process for preparation of 2,2,2-trifluoroacetamide by reacting ethyl trifluoroacetate with gaseous ammonia at 0oC. The reaction mixture was stored at ambient temperature for 20 hours and thereafter 2,2,2-trifluoroacetamide was isolated after ethanol forerun. The prior art process provides a low yield of 83%, thus making the process unsuitable at commercial scale. Additionally, ethanol produced as a by-product is difficult to remove from the main product resulting in difficulty in scale-up operations along with loss of yield
Thus, there is a need in the art to provide simple, cost-effective and industrially scalable process for the preparation of compound of Formula I.
Summary of the Invention
The present invention provides a process for the preparation of pure haloacetamide of Formula I comprising,

Formula I
a) contacting ethyl trifluoroacetate with gaseous ammonia at a temperature range of 0oC to 50oC to obtain a reaction mixture,
b) removing ethanol from step a) reaction mixture to obtain second reaction mixture,
c) contacting cyclohexane to form azeotropic mixture of ethanol and cyclohexane,
d) removing azeotropic mixture of ethanol and cyclohexane from step c) reaction mixture to obtain haloacetamide of Formula I, and
e) isolating haloacetamide of Formula I from step d).
Detailed Description of the Invention
In an aspect, the present invention provides a process for the preparation of pure haloacetamide of Formula I comprising,

Formula I
a) contacting ethyl trifluoroacetate with gaseous ammonia at a temperature range of 0oC to 50oC to obtain a reaction mixture,
b) removing ethanol from step a) reaction mixture to obtain second reaction mixture,
c) contacting cyclohexane to form azeotropic mixture of ethanol and cyclohexane,
d) removing azeotropic mixture of ethanol and cyclohexane from step c) reaction mixture to obtain haloacetamide of Formula I, and
e) isolating haloacetamide of Formula I from step d).
The ethyl trifluoroacetate of step a) may be obtained commercially or may be prepared by any method known in the art.
The ethanol in step b) may be removed at a temperature of about 40-50oC under vacuum at 500-600 mmHg for about 1 hour to about 2 hours.
The step d) may take place at the temperature of about 40-50oC under vacuum at 500-600 mmHg for about 1 hour to about 2 hours.
The haloacetamide of Formula I is isolated from step d) reaction mixture. The haloacetamide of Formula I may be isolated by filtration, evaporation, sublimation, concentration, crystallization and re-crystallization or mixture thereof.
The haloacetamide of Formula I, as purified by present invention, has a purity greater than about 98%, preferably greater than 98.5% by gas chromatography.
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
The ethyl trifluoroacetate (142 g) was added to a round bottomed flask and the solution was cooled to 0oC. The ammonia gas was purged in the reaction mixture and the temperature was maintained below 40oC for 1 hour to 2 hours. The ethanol (37 g) was recovered from the reaction mixture at 40 under vacuum at 600 mmHg for 1 hour to 2 hours. The cyclohexane was added to the remaining mixture and an azeotropic mixture of ethanol and cyclohexane was formed. The azeotrope was distilled out 40 under vacuum at 600 mmHg for 1 hour to 2 hours. The title compound was obtained after filteration.
Yield (%): 94
Purity (%): 99.0

CLAIMS:
We claim:
1. A process for the preparation of pure haloacetamide of Formula I comprising,

Formula I
a) contacting ethyl trifluoroacetate with gaseous ammonia at a temperature in the range of 0oC to 50oC to obtain a reaction mixture,
b) removing ethanol from step a) reaction mixture to obtain a second reaction mixture,
c) contacting cyclohexane to form azeotropic mixture of ethanol and cyclohexane,
d) removing azeotropic mixture of ethanol and cyclohexane from step c) reaction mixture to obtain haloacetamide of Formula I, and
e) isolating haloacetamide of Formula I from step d).
2. The process as claimed in claim 1, wherein the ethanol in step b) is removed at a temperature in the range of 40 to 50oC under vacuum at 500-600 mmHg.
3. The process as claimed in claim 1, wherein the step d) takes place at the temperature in the range of 40 to 50oC under vacuum at 500-600 mmHg.
4. The process as claimed in claim 1, wherein the compound of Formula I is isolated from step d) by filtration, evaporation, sublimation, concentration, crystallization and re-crystallization or mixture thereof.
5. The process as claimed in claim 1, wherein the compound of Formula I, as purified by present invention, has a purity greater than about 98%.