Acetic Acid → 7,8-Difluoro-1-methoxy-4-oxo-1,4-dihydro-benzo[b][1,8]naphthyridine-3-carboxylic acid

Participants

Reaction Conditions

Reaction Steps

A suspension of 3-ethoxycarbonyl-7,8-difluoro-1-methoxy-4-oxo-1,4-dihydrobenzo[b][1,8]-naphthyridine (2.78 g) in 17.5% strength hydrochloric acid (30 cc) and acetic acid (30 cc) is heated to a temperature in the region of 100° C. for 1 hour. After cooling to approximately 20° C., the reaction mixture is poured into water (100 cc). The precipitate formed is drained and washed with water (3×+cc) and ethanol (2×5cc). After 1 recrystallization in dimethylformamide (100 cc) containing ethanol (20%), 7,8-difluoro-1-methoxy-4-oxo-1,4-dihydrobenzo[b][1,8]-naphthyridine-3-carboxylic acid (2.03 g) is obtained in the form of a yellow solid, m.p. 325°-327° C.

Provenance & Evidence