Construction of highly substituted pyrazole derivatives with P-C bond: access to racemic and enantioselective forms by conjugate addition of diarylphosphane oxides to α,β-unsaturated pyrazolones

The synthesis of organophosphorus compounds is of great importance to industrial, agricultural, and pharmaceutical chemistry. In this paper, we have reported the synthesis of highly substituted pyrazole derivatives through P-C bond formation under catalyst-free conditions. On the other hand, the first catalytic asymmetric version of this reaction has also been developed under catalysis by an isosteviol derived thiourea organocatalyst. The optically active phosphorus-containing compounds have been obtained in good chemical yields with moderate enantioselectivities. (C) 2013 Elsevier Ltd. All rights reserved.