Dimethylformamide → 6,8-Difluoro-1-(2-fluoroethyl)-1,4-dihydro-7-(4-hydroxypiperazin-1-yl)-4-oxoquinoline-3-carboxylic acid

Participants

Reaction Steps

1-Hydroxypiperazine dihydrochloride (1.03 g), triethylamine (35.6 g) and dimethylformamide (85 ml) are added to 6,7,8-trifluoro-1-(2-fluoroethyl)-1,4-dihydro-4-oxoquinoline-3-carboxylic acid (8.5 g), which is prepared by the procedure described in Japanese Patent First Publication No. 30964/1981, and the mixture is stirred for 1.5 hours at 100°-105° C. After cooling to room temperature, the reaction mixture is poured into ice-water (500 ml) and the pH is adjusted to 7.0 with 50% aqueous acetic acid. The resulting precipitate is filtered, washed with water and then recrystallized from dimethylformamide. Ethanol (100 ml) is added to the resulting pale yellow needles and the mixture is refluxed for 1.5 hours. After cooling the mixture to room temperature, the insoluble substance is filtered to yield 6,8-difluoro-1-(2-fluoroethyl)-1,4-dihydro-7-(4-hydroxypiperazin-1-yl)-4-oxoquinoline-3-carboxylic acid (3.7 g) as pale yellow needles, m.p. 220°-229° C. (decomposition).

Provenance & Evidence