Copper-Mediated Domino Cyclization/Trifluoromethylation/Deprotection with TMSCF<sub>3</sub>: Synthesis of 4‑(Trifluoromethyl)pyrazoles

A copper-mediated synthesis of 4-(tri­fluoro­methyl)­pyrazoles is described. In one step from readily accessible α,β-alkynic tosylhydrazones, a remarkable domino sequence of cyclization, trifluoromethylation, and detosylation takes place to furnish the 4-CF<sub>3</sub> <i>N</i>-H pyrazole cores with good functional group compatibility. The reaction conditions are mild and convenient, at room temperature in air, using the commercially available trifluoromethyltrimethylsilane (TMSCF<sub>3</sub>) as the CF<sub>3</sub> source. The method can be applied to the synthesis of a 4-CF<sub>3</sub> analogue of the anti-inflammatory drug celecoxib.