Method for the production of 2,6-dichloro-5-fluoro-nicotinic acid and coarse and particularly pure 2,6-dichloro-5-fluoro-nicotinic acid

Abstract

The invention relates to a method for the production of 2,6-dichloro-5-fluoronicotinic acid by hydrolyzing 2,6-dichloro-5-fluoro-3-cyanopyridine by (a) dissolving 2,6-dichloro-5-fluoro-3-cyanopyridine at 70 to 90° C. in sulfuric acid having a concentration of 90 to 99% by weight and hydrolyzing the 2,6-dichloro-5-fluoro-3-cyanopyridine at 70 to 100° C. to the corresponding carboxamide, (b) cooling the resultant reaction mixture to a temperature in the range from 10 to 65° C., (c) metering in water until the concentration of sulfuric acid is 55 to 75% by weight (calculated relative to the sulfuric acid employed in stage (a) and the water employed in stage (c)) while keeping the temperature between 30 and 65° C. during the addition of the first quarter of the water and keeping the temperature between 50 and 80° C. during the addition of the second quarter of the water, and (d) completing hydrolysis of the resultant mixture to 2,6-dichloro-5-fluoronicotinic acid at 70 to 110° C.

Dependencies are inferred from the claim text.