Direct Access for the Regio- and Stereoselective Synthesis of N-Alkenylpyrazoles and Chromenopyrazoles

A highly regio- and stereoselective method was developed for the preparation of N-alkenylpyrazoles and chromenopyrazoles by the reaction of N-tosylhydrazones and salicyl N-tosylhydrazones with alkynes under neat conditions in the presence of La(OTf)(3). The present study was found to be efficient and convenient for direct access to N-alkenylpyrazoles and chromenopyrazoles through C-C, C-N, and C-O bond forming reactions. Structure assignment of N-alkenylpyrazole compound 5c was confirmed by X-ray analysis.

Automated summary

A highly regio- and stereoselective method was developed for the preparation of N-alkenylpyrazoles and chromenopyrazoles by reacting N-tosylhydrazones and salicyl N-tosylhydrazones with alkynes in the presence of La(OTf)(3) under neat conditions. This study proved to be efficient and convenient for direct access to N-alkenylpyrazoles and chromenopyrazoles through C-C, C-N, and C-O bond forming reactions, with the structure of compound 5c confirmed by X-ray analysis.