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

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Reaction Steps

A solution, at about 2° C., of 14.6 g of ethylamine in 200 cm3 of ethanol is added in the course of 10 minutes, at between 2° and 5° C., with stirring, to a suspension of 20 g of ethyl 2-(2-chloro-6,7-difluoroquinoline-3-carbonyl)-3-dimethylaminoacrylate in 200 cm3 of ethanol at about 2° C., the mixture is stirred for a further 40 minutes at between 2° and 5° C. and the temperature is then allowed to rise to about 20° C. in the course of 2 hours. After 24 hours at about 20° C., the insoluble matter is drained and washed with 2 times 30 cm3 of ethanol and 2 times 50 cm3 of diisopropyl ether. 16.35 g of 3-ethoxycarbonyl-1-ethyl-7,8-difluoro-4-oxo-1,4-dihydrobenzo[b][1,8]naphthridine are obtained in the form of a beige solid melting at 290° C.

Provenance & Evidence