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.