Chloroacetic Acid → HCID 70363008, compound

Participants

Reaction Conditions

Reaction Steps

A mixture f 150 parts of 2-aminobenzothiazole, 150 parts of solid sodium hydroxide and 300 parts of ethylene glycol is stirred for 6 hours at 130°-140° C. (Example 1 of European Pat. No. 0,039,483). The mixture is cooled to 45° C., 113 parts of chloroacetic acid are added so that the internal temperature does not exceed 50° C., and stirring is then continued for 2 hours at this temperature. The mixture is then heated to 80°-90° C. and kept at this temperature for 1 hour, and the resulting suspension of the sodium salt of 2-aminophenyl thioglycolic acid of the formula (11) is then allowed to run into a mixture of 2500 parts of water and 550 parts of 30% strength hydrochloric acid, the temperature increasing to 60° C. During this procedure, the 2-aminophenyl thioglycolic acid liberated undergoes rapid cyclization to give 3-oxo-dihydrobenzothiazine of the formula (12), which is the stable anhydride of the unstable free acid: ##STR22## Stirring is continued for 30 minutes at 60° to 70° C., the mixture is cooled to room temperature and the precipitated product is filtered off, washed neutral with water and dried at 120° C. in a through-circulation oven. 150 parts of 3-oxo-dihydrobenzothiazine of melting point 175° C. are obtained; this corresponds to a yield of 90.0% of theory, based on 2-aminobenzothiazole employed.

Provenance & Evidence