Isobutyl chloroformate → 6-(4-Benzyl-1-piperazinylcarbonyl)carbostyril monohydrochloride monohydrate

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Reaction Steps

34.5 Grams of 6-carboxycarbostyril and 31 ml of triethylamine were dissolved in 350 ml of dimethylformamide and stirred at a room temperature. Then 28 ml of isobutyl chloroformate in 14 ml of dimethylformamide solution was added dropwise to the former solution. After stirring at a room temperature for 1 hour, 37 g of benzylpiperazine in 21 ml of dimethylformamide solution was added dropwise to the reaction mixture and stirred at a room temperature for 10 hours. The reaction mixture was poured into a saturated sodium bicarbonate aqueous solution, then extracted with chloroform. The chloroform layer was washed with water and a saturated sodium chloride aqueous solution in this order and the chloroform extract was dried with anhydrous sodium sulfate. The solvent was removed by distillation under a reduced pressure, the residue thus obtained was crystallized by adding ether and the crystals were collected by filtration. The crystals were dissolved in methanol and the pH of the solution was adjusted to about pH 1 by adding concentrated hydrochloric acid. The crude crystals thus obtained were recrystallized from ethanol-water to obtain 30.1 g of 6-(4-benzyl-1-piperazinylcarbonyl)carbostyril monohydrochloride monohydrate. Colorless granular crystals. Melting point: over 300° C.

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