Hydrochloric Acid → 8-Chloro-7-fluoro-1-methyl-4-oxo-1,4-dihydrobenzo[b][1,8]naphthyridine-3-carboxylic acid

Participants

Reaction Conditions

Reaction Steps

A suspension of 8-chloro-3-ethoxycarbonyl-7-fluoro-1-methyl-4-oxo-1,4-dihydrobenzo[b][1,8]-naphthyridine (15 g) in acetic acid (150 cc) and 17.5% strength aqueous hydrochloric acid solution (150 cc) is heated to a temperature in the region of 100° C. with stirring for 4 hours. After cooling to a temperature in the region of 20° C., the product is drained, washed with water (2×100 cc) and washed with ethanol (2×150 cc) and then ethyl ether (2×100 cc). 8-Chloro-7-fluoro-1-methyl-4-oxo-1,4-dihydrobenzo[b][1,8]naphthyridine-3-carboxylic acid (12.7 g) is obtained in the form of a beige solid, subliming at 400°-405° C., which is used without further purification for the subsequent steps.

Provenance & Evidence