Tetrahedron

A regioselective synthesis of 5-pyrazolones and pyrazoles from phosphazenes derived from hydrazines and acetylenic esters

F Palacios, AMO de Retana, J Pagalday

Index: Palacios, Francisco; Ochoa De Retana, Ana M.; Pagalday, Jaione Tetrahedron, 1999 , vol. 55, # 50 p. 14451 - 14458

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Citation Number: 36

Abstract

Efficient and regioselective syntheses of 1-phenyl-5-pyrazolones substituted with a phosphoranylidene group in the 3-position and of 3-alkoxycarbonyl-5-methoxy-1-phenyl pyrazoles are described. The key step is the formation of functionalized hydrazones by [2+ 2] cycloaddition reaction of phosphazenes derived from hydrazines with acetylenic esters. Subsequent cyclization of these compounds with butyl lithium affords substituted 5- ...