Stereoselective organocatalytic sulfa-Michael reactions of aryl substituted α,β-unsaturated N-acyl pyrazoles

Abstract

The asymmetric Michael addition of aryl thiols and thioacetic acid to challenging β- or α,β-aryl substituted α,β-unsaturated N-acyl pyrazoles catalysed by bifunctional organocatalysts has been investigated. The corresponding sulfide derivatives are obtained under mild and simple conditions, using readily available amine-thioureas or squaramides with good to high stereocontrol (up to 89/11 dr and 98% ee). The protocols complement the few pre-existing methods reported for the asymmetric access to β-thio-derivatives of α,β-unsaturated esters or their ester equivalents.