3-Ethoxycarbonyl-7,8,9-trifluoro-1-methyl-4-oxo-1,4-dihydrobenzo[b][1,8]naphthyridine → 7,8,9-Trifluoro-1-methyl-4-oxo-1,4-dihydrobenzo[b][1,8]naphthyridine-3-carboxylic acid

Participants

Reaction Conditions

Reaction Steps

A suspension of 0.88 g of 3-ethoxycarbonyl-7,8,9-trifluoro-1-methyl-4-oxo-1,4-dihydrobenzo-[b][1,8]naphthyridine in a mixture of 10 cm3 of 17.5% aqueous hydrochloric acid solution and 10 cm3 of acetic acid is heated with stirring to a temperature in the region of 100° C. for 3 hours. After cooling to approximately 20° C., the product is drained and washed with 3 times 10 cm3 of water. 0.75 g of 7,8,9-trifluoro-1-methyl-4-oxo-1,4-dihydrobenzo[b][1,8]naphthyridine-3carboxylic acid is obtained in the form of a pale yellow solid, which decomposes at 352° C. and which is used without further purification for the subsequent steps.

Provenance & Evidence