Synthesis of Trifluoromethylated Pyrazolidines, Pyrazolines and Pyrazoles via Divergent Reaction of β-CF₃-1,3-Enynes with Hydrazines

Abstract

Three types of trifluoromethylated pyrazolidines, pyrazolines, and pyrazoles can be synthesized via divergent reaction of β-CF3-1, 3-enyne with hydrazines. The reaction with simple hydrazine monohydrate or sulfonyl hydrazines as nucleophiles produces 1,3,4-trisubstituted pyrazolines, whereas the reaction with acetyl hydrazine as nucleophiles affords 1,4,5-trisubstituted pyrazolidines. Using phenylhydrazine or tert-butylhydrazine as a reaction partner, the products are easily oxidized to form 1,4,5-trisubstituted pyrazoles.