Carbo[3 + 3] cyclocondensation reactions. A new method for the synthesis of tetrahydropyrazolo[1,5-b]quinazolines and tetrahydropyrazolo[4,5-b]quinolines

Abstract

The cyclocondensation of substituted 5-aminopyrazoles with benzylidene acetone leads to the regioselective synthesis of dihydropyrazolo[1,5-a]pyrimidines and dihydropyrazolo[3,4-b]pyridines containing a methyl group in the six-membered heterocycle. Compounds of both these groups readily undergo carbo[3 + 3] cyclo-condensation with chalcones in butanol under alkaline catalysis conditions and upon heating to give aryl-substituted tetrahydropyrazolo[1,5-b]quinazolines and tetrahydropyrazolo[4,5-b]quinolines. Ultrasonic initiation of these reactions leads to enhanced rate and higher yield of the desired products.