Hydrochloric Acid → Ibafloxacin

Participants

Reaction Conditions

Reaction Steps

A mixture of 9.3 g of 6-fluoro-5-methyl-1,2,3,4-tetrahydroquinaldine and 17 ml of diethyl ethoxymethylenemalonate was heated at 150°-160° C. for 3.5 hours, and then cooled to 100° C. To this solution was added 56 g of polyphosphoric acid, and the mixture was stirred for one hour while heating on a steam bath. The mixture was then cooled to room temperature and allowed to stand for about 72 hours. To this mixture, containing ethyl 1,2-dihydro-5,8-dimethyl-9-fluoro-1-oxo-1H,5H-benzo[ij]quinolizine-2-carboxylate, was added 250 ml of 20% aqueous sodium hydroxide to make the solution basic. The solution was then heated at its reflux temperature for 2 hours, cooled, and acidified with concentrated hydrochloric acid. The solid was separated by filtration and recrystallized from aqueous N,N-dimethylformamide. Washing with ethanol followed by drying provided 6,7-dihydro-5,8-dimethyl-9-fluoro-1-oxo-1H,5H-benzo[ij]quinolizine-2-carboxylic acid as an off-white solid, m.p. 269°-272° C. Analysis: Calculated for C15H14FNO3 : %C, 65.4; %H, 5.1; %N, 5.1; Found: %C, 65.0; %H, 5.0; %N, 5.0.

Provenance & Evidence