γ-Alumina as a recyclable catalyst for the four-component synthesis of 6-amino-4-alkyl/aryl-3-methyl-2,4-dihydropyrano[2,3-c]pyrazole-5-carbonitriles in aqueous medium

gamma-Alumina as an expedient and recyclable catalyst for the synthesis of 6-amino-4-alkyl/aryl-3-methyl-2,4-dihydropyrano[2,3-c]pyrazole-5-carbonitriles in water via a four-component reaction is established. Comparative study of the efficacy of gamma-alumina, basic alumina and KF-alumina is also discussed. The method presented is mild, environment friendly, inexpensive and functionality tolerable to give the products in good to excellent yields. (C) 2011 Elsevier Ltd. All rights reserved.