3-Ethoxycarbonyl-7,8-difluoro-1-ethyl-4-oxo-1,4-dihydrobenzo[b][1,8]naphthyridine → 1-Ethyl-7,8-difluoro-4-oxo-1,4-dihydrobenzo[b][1,8]naphthyridine-3-carboxylic acid

Participants

Reaction Conditions

Reaction Steps

A suspension of 8 g of 3-ethoxycarbonyl-1-ethyl-7,8-difluoro-4-oxo-1,4-dihydro-benzo[b][1,8]naphthyridine in 80 cm3 of 17.5% hydrochloric acid and 80 cm3 of acetic acid is heated, with stirring, at a temperature close to 100 hour and 30 minutes. After cooling to about 20° C., the insoluble matter is drained, washed with 3 times 20 cm3 of water and recrystallized from 50 cm3 of dimethylformamide. 6.3 g of 1-ethyl-7,8-difluoro-4-oxo-1,4-dihydro-benzo[b][1,8]naphthyridine-3-carboxylic acid are obtained in the form of a yellow solid melting at 330° C.

Provenance & Evidence