Diisopropyl Ether → 1-Cyclopropyl-3-ethoxycarbonyl-7,8-difluoro-4-oxo-1,4-dihydrobenzo[b][1,8]naphthyridine

Participants

Reaction Conditions

Reaction Steps

A stirred suspension of 5.27 g of ethyl 2-(2-chloro-6,7-difluoroquinoline-3-carbonyl)-3-cyclopropylaminoacrylate in 2.22 g of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and 120 cm3 of ethanol is heated at a temperature close to 75° C. for 35 minutes. After cooling to about 20° C., the reaction mixture is taken up in 100 cm3 of water and extracted once with 100 cm3 and twice with 50 cm3 of trichloromethane. The combined organic extracts are washed with 3 times 50 cm3 of water, dried over magnesium sulphate, filtered and concentrated under reduced pressure (20 kPa) at a temperature close to 20° C. The dry extract obtained is taken up in 30 cm' of diisopropyl ether, drained and recrystallized from a mixture of 75 cm3 of ethanol and 75 cm3 of dimethylformamide. 3.57 g of 1-cyclopropyl-3-ethoxycarbonyl-7,8-difluoro-4-oxo-1,4-dihydro-benzo[b][1,8]naphthyridine are obtained in the form of a yellow solid melting at 229°-230° C.

Provenance & Evidence