Regioselective synthesis of multisubstituted pyrazoles via cyclocondensation of beta-thioalkyl-alpha,beta-unsaturated ketones with hydrazines

Multisubstituted pyrazoles were efficiently synthesized by cyclocondensation of beta-thioalkyl-alpha,beta-unsaturated ketones with hydrazines under relatively mild conditions. A one-pot synthetic protocol through tandem Liebeskind-Srogl cross-coupling/cyclocondensation using alpha-oxo ketene dithioacetals as the starting materials was also realized for the same purpose. (C) 2011 Elsevier Ltd. All rights reserved