Zinc-Catalysed (3+2) Cycloaddition of Enaminone with Tosylhydrazide to Synthesise 1H-Pyrazole via C−N and S−N Bond Cleavage

A novel and practical zinc-catalysed synthesis of 1H-pyrazole has been developed. The one-pot protocol enables the cycloaddition of enaminone and tosylhydrazide via C−N and S−N bond breaking process, leading to diverse mono-substituted pyrazole derivatives in high yields. Moreover, the easily accessible materials, broad substrate scope with excellent functional group tolerance, ease of isolation and open-air conditions are the key features of the present method.