DBU mediated confluent approach for the one pot synthesis of novel 5-hydroxy pyrazolo[1,2-a][1,2,4]triazoles and their dehydration to novel pyrazolo[1,2-a][1,2,4]triazole derivatives

A series of novel alkyl 5-hydroxy-7-aryl-5-methyl-1,3-dioxo-2-phenyl hexahydropyrazolo[1,2-a][1,2,4] triazole-6-carboxylates and alkyl 5-aryl-7-methyl-1,3-dioxo-2-phenyl-1,2,3,5-tetra hydropyrazolo[1,2-a] [1,2,4]triazole-6-carboxylates have been synthesized. The synthesis of hydroxy pyrazolo[1,2-a][1,2,4] triazoles has been achieved by DBU mediated one pot reaction of aromatic aldehydes, alkyl acetoacetates and 4-phenylurazole at 35 degrees C in ethanol-water (1:1). Dehydration of hydroxy pyrazolo[1,2-a][1,2,4]-triazoles has been achieved using conc. H2SO4 to afford dehydrated pyrazolo[1,2-a][1,2,4]triazoles in high yields. The structural assignments have been made by spectral data and unambiguously confirmed by X-ray analysis. Good yields, operational simplicity and moderate conditions are the advantages of the reactions. (C) 2016 Elsevier Ltd. All rights reserved.