2,2,2-Trifluoroethylhydrazine → 3,3a,4,5,6,7-Hexahydro-3-phenyl-5-(2-phenylethyl)-7-(phenylmethylene)-2-(2,2,2-trifluoroethyl)-2H-pyrazolo-[4,3-c]pyridine

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Reaction Steps

Ten grams of 3,5-dibenzylidene-1-(2-phenylethyl)-4-piperidone monohydrochloride and 4.4 g of 70% aqueous 2,2,2-trifluoroethylhydrazine are reacted in 150 ml of methanol at reflux for 4 hours. The solvent is removed on a rotary evaporator leaving 13.1 g of brittle residue. The material is converted to 10.7 g of free base using potassium carbonate and ether extractions. The free base is dissolved in 50 ml of warm isopropyl ether and diluted with 20 ml of hexane. After the solution is cooled to room temperature, seeded and rubbed, the crystalline base gradually separates. After cooling overnight, the solid is filtered, washed with cold 5:2 isopropyl ether-hexane and dried to yield 3.6 g of product, melting point 113°-114° C, sintering at 105° C.

Provenance & Evidence