Direct Regioselective [3 + 2] Cycloaddition Reactions of Masked Difluorodiazoethane with Electron-Deficient Alkynes and Alkenes: Synthesis of Difluoromethyl-Substituted Pyrazoles

Phenylsulfone difluorodiazoethane (PhSO₂CF₂CHN₂), an easy-to-prepare and bench-stable masked CF₂-building block, has been developed. The synthetic utility of this reagent is demonstrated by a direct regioselective [3 + 2] cycloaddition with electron-deficient alkynes and alkenes. This protocol enables facile construction of an array of difluoromethyl-substituted pyrazoles in good to high yields under mild reaction conditions