Synthesis of polysubstituted pyrazoles by a platinum-catalyzed sigmatropic rearrangement/cyclization cascade.

A highly efficient Pt-catalyzed [3,3] sigmatropic rearrangement/cyclization cascade of N-propargylhydrazones is reported. The process provides expedient access to a variety of highly functionalized pyrazoles. The substrate has good substituted group compatibility, and the bioactive 3-CF3 pyrazoles could be synthesized easily with this method.