A Complementary Approach to 3,5-Substituted Pyrazoles with Tosylhydrazones and Terminal Alkynes Mediated by TfOH

A complementary method for the preparation of 3,5-substituted pyrazoles in moderate to high yields has been explored via TfOH-induced addition of tosylhydrazones to the terminal alkynes. This acid-induced addition procedure might be an operationally safe alternative compared to typical 1,3-dipolar cycloaddition as there is no involvement of diazo compounds.