Hydrochloric Acid → 8-(4-trifluoromethyl-1-piperazinyl)-6,7-dihydro-1-oxo-1H,5H-benzo[ij]quinolizine-2-carboxylic acid

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Reaction Steps

A mixture of 3.4 g of 8-(p-toluenesulfonyloxy)-6,7-dihydro-1-oxo-1H,5H-benzo[ij]quinolizine-2-carboxylic acid, 9.1 g of 1-trifluoromethylpiperazine and 200 ml of anhydrous dimethyl sulfoxide was heated with stirring in an autoclave at 150° to 160° C. for 18 hours under nitrogen gas flow at a pressure of 10 atms. After completion of the reaction, the solvent and excessive piperazine compound were removed by distillation under reduced pressure and a mixture of methanol and ethanol was added to the residue. The precipitates formed were collected by filtration and washed with ether. The crystals obtained were suspended in a mixture of 200 ml of water and 40 ml of a 10% aqueous hydrochloric acid solution and insoluble substances were removed by filtration. The filtrate was rendered neutral with saturated aqueous solution of sodium bicarbonate and purified through column chromatography using Amberlite LH-20 (a trade name for a product of Tokyo Organic Chemical Industries Ltd.) (eluent: water, ethanol). Recrystallization of the eluate from dimethylformamide gave 1.7 g of 8-(4-trifluoromethyl-1-piperazinyl)-6,7-dihydro-1-oxo-1H,5H-benzo[ij]quinolizine-2-carboxylic acid as white rhombic crystals having a melting point of 300° C. or more.

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