Ethanol → 3-Ethoxy-7,8-difluoro-1-methyl-4-oxo-1,4-dihydrobenzo[b][1,8]naphthyridine

Participants

Reaction Conditions

Reaction Steps

A solution of 3.78 g of potassium iodide in 20 cm3 of water is added with stirring at approximately 20° C. to a suspension of 71 g of 3-ethoxycarbonyl-7,8-difluoro-1-methyl-4-oxo-1,2,3,4-tetrahydrobenzo[b][1,8]naphthyridine in 1,000 cm3 of ethanol. The suspension is heated to 77° C., and 30 cm3 of 33% by weight hydrogen peroxide is added in the course of 60 minutes at this temperature. The reaction mixture is kept refluxing for a further 30 minutes and is then cooled to approximately 20° C. A solution of 11.4 g of sodium thiosulphate in 50 cm3 of water is introduced in the course of 5 minutes at this temperature. The precipitate obtained is drained at approximately 20° C. and washed with twice 300 cm3 of water. The wet product obtained is dried under reduced pressure (20 kPa) at approximately 60° C. 73 g of 3-ethoxy-7,8-difluoro-1-methyl-4-oxo-1,4-dihydro-benzo[b][1,8]naphthyridine are isolated in the form of a white solid, melting point above 270° C.

Provenance & Evidence