Cascade Oxidation/Halogenoaminocyclization Reaction of Trifluoromethylated Homoallylic N-Acylhydrazines: Metal-free Synthesis of CF3-Substituted Pyrazolines.

An efficient and practical cascade oxidation/halogenoaminocyclization of trifluoromethylated homoallylic N-acylhydrazines is developed. The protocol enables an efficient access to various biologically interesting CF3-containing pyrazoline compounds from readily accessible trifluoromethylated homoallylic N-acylhydrazines in good to excellent yields under mild conditions without any other additives or catalysts. The produced pyrazoline compounds can be further manipulated to other more complicated derivatives through transformation of residual halogen atom.