Acetic Acid → 3-Ethoxycarbonyl-7,8-difluoro-1-methyl-4-oxo-1,2,3,4-tetrahydrobenzo[b][1,8]naphthyridine

Participants

Reaction Conditions

Reaction Steps

A solution of 94 g of 3-ethoxycarbonyl-6,7-difluoro-2-[N-methyl-N-(b-ethoxycarbonylethyl)amino]quinoline in 300 cm3 of absolute ethanol is added in the course of 80 minutes to a solution of 26.6 g of sodium ethylate brought to reflux in 900 cm3 of absolute ethanol. The suspension obtained, still refluxing, is stirred for a further 15 minutes. 38 cm3 of glacial acetic acid are then introduced in the course of 30 minutes. The reaction mixture is stirred for a further 15 minutes and, with the mixture still refluxing, 500 cm3 of water are then introduced in the course of 45 minutes. The suspension obtained is cooled to approximately 20° C. The precipitate is drained at approximately 20° C. and washed with twice 300 cm3 of water. The wet product is dried under reduced pressure (20 kPa) at approximately 60° C. 71.5 g of 3-ethoxycarbonyl-7,8-difluoro-1-methyl- 4-oxo-1,2,3,4-tetrahydro-benzo[b][1,8]naphthyridine are isolated in the form of a yellow solid, melting point 188° C.

Provenance & Evidence