An efficient synthesis of 4-substituted pyrazolyl-3,4-dihydropyrimidin-2(1H)-(thio)ones catalyzed by Mg(ClO4)2 under ultrasound irradiation

A simple method for the one-pot, three-component Biginelli condensation reaction of 5-chloro/phenoxyl-3-methyl-1-phenyl-4-formylpyrazole, a 1,3-dicarbonyl compound and urea or thiourea is described, employing Magnesium perchlorate [Mg(ClO4)(2)] as an efficient catalyst under ultrasound irradiation. A novel series of 4-substituted pyrazolyl-3,4-dihydropyrimidin-2(1H)-(thio)ones have been synthesized in moderate yields. The catalyst exhibited remarkable reactivity and can be recycled. (c) 2006 Elsevier B.V. All rights reserved.