Triethylamine → 1,4-Dihydro-6,7-dimethoxy-4-oxo-N-(2-oxo-1-imidazolidinyl)-3-quinolinecarboxamide

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Reaction Conditions

Reaction Steps

To a suspension of 1,4-dihydro-6,7-dimethoxy-4-oxo-3-quinolinecarboxylic acid (39.9 g, 0.160 mol) in 3.2 l of N,N-dimethylformamide, triethylamine (32.4 g, 0.320 mol) was added. At 0° C. and under nitrogen protection, diphenyl chlorophosphate (43.0 g, 0.160 mol) was added dropwise and the mixture was stirred for 6 hours at 0° C. A solution of N-amino-imidazolidine-2-one (16.2 g, 0.160 mol) in N,N-dimethylformamide was added and stirring was continued at 0° C. overnight. The triethyl ammonium salt (26 g) was filtered off and the filtrate evaporated in vacuo. The residual oil was triturated with 1 l of ethyl acetate and 1 l of water. The resulting solid was filtered off, washed with water and ethyl acetate and dried in vacuo. The crude product was stirred with 270 ml of 0.2N sodium hydroxide solution of 2 days, filtered off, washed with water and dried in vacuo to give 23.2 g of the title compound, melting point>300° C.

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