Regioselective [3 + 2]-annulation of hydrazonyl chlorides with 1,3-dicarbonyl compounds for assembling of polysubstituted pyrazoles

Abstract

A facile approach to polysubstituted pyrazoles from hydrazonyl chlorides and 1,3-dicarbonyl compounds has been developed. In the presence of DMAP combined with Et₃N, hydrazonyl chlorides reacted with N-phenyl-3-oxobutanamides smoothly to afford a series of polysubstituted pyrazoles in 67–98% yields via the [3 + 2]-cycloaddition.