One-pot three-component synthesis of pyrazoles through a tandem coupling-cyclocondensation sequence

An efficient and general one-pot procedure for the synthesis of pyrazoles from acid chlorides, terminal alkynes and hydrazines was described via a coupling and cyclocondensation sequence. Acid chlorides coupled with terminal alkynes to give alpha,beta-unsaturated ynones, and in situ converted into pyrazoles by the cycloaddition of hydrazines. The desired pyrazoles were obtained with 15-85% isolated yields. (C) 2008 Published by Elsevier Ltd.