Silver(I)-catalyzed facile synthesis of pyrazoles from propargyl N-sulfonylhydrazones.

A silver(I)-catalyzed facile formation of pyrazoles from propargyl N-sulfonylhydrazones has been disclosed. During the reaction, a migration of sulfonyl groups (Ts, Ms) was observed. Good functional group compatibility was observed under mild reaction conditions (at room temperature for 3-5 h). This methodology allows for the efficient and regioselective synthesis of 1,3- and 1,5-disubstituted and 1,3,5-trisubstituted pyrazoles.