Synthesis of Trifluoroethyl Pyrazolines via Trichloroisocyanuric Acid Promoted Cascade Cyclization/Trifluoromethylation of β,γ-Unsaturated Hydrazones.

A novel and efficient protocol for the construction of trifluoroethyl pyrazolines has been developed by cascade cyclization/trifluoromethylation reaction of β,γ-unsaturated hydrazones. This strategy uses cheap and commercially available trichloroisocyanuric acid as promoter and TMSCF3 as the trifluoromethylating reagent, which make the trifluoromethylating process much cheaper. A wide range of substrates can be applied in this process to afford the trifluoroethyl pyrazolines in good yield.