Sodium cyanoborohydride → 4,5-Dihydro-7-phenylpyrazolo[1,5-a]pyrimidine-3-carboxamide

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Reaction Steps

A 6.0 g amount of 7-phenylpyrazolo[1,5-a]-pyrimidine-3-carboxamide (prepared as described in Example 2) was stirred under nitrogen as a suspension in 120 ml of glacial acetic acid (cooled in an ice bath) and then 3.5 g of sodium cyanoborohydride was added to the reaction mixture in portions. After one hour of stirring in the ice bath, the mixture was stirred at room temperature for 3.5 hours at which time the original solid dissolved. Stirring was continued for one hour longer then the solution was concentrated in vacuo. Water was added to the residue and a precipitate formed. The precipitate was collected by filtration and then was dissolved in dichloromethane. The organic solution was washed with a saturated solution of sodium bicarbonate, dried over anhydrous sodium sulfate and filtered. The filtrate was evaporated in vacuo to give a solid. The solid was recrystallized from isopropyl alcohol to give 5.0 g of the desired product as a white solid, m.p. 149°-152° C.

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