Regioselective Synthesis of 3‐Trifluoromethyl 4‐Subtituted Pyrazoles by [3+2] Cycloaddition of Trifluoroacetonitrile Imines and Nitroalkenes

An efficient cycloaddition reaction of trifluoroacetohydrazonoyl bromides with nitroolefins was developed, which regioselectively produced 3‐trifluoromethyl‐4‐substituted pyrazoles. The reaction has the advantages of mild conditions, good tolerance of functional groups and simple operation. 3‐Trifluoromethyl‐4‐substituted pyrazoleswere synthesized by regioselective [3+2] cycloaddition of in situgenerated trifluoroacetonitrile imines with nitroolefins under mild reaction conditions. This reaction has good scalability and tolerance.