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Copper-Mediated Domino Cyclization/Trifluoromethylation/Deprotection with TMSCF3: Synthesis of 4‑(Trifluoromethyl)pyrazoles

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journal contribution
posted on 2017-01-12, 18:48 authored by Quande Wang, Lisi He, Kin Keung Li, Gavin Chit Tsui
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-CF3 N-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 (TMSCF3) as the CF3 source. The method can be applied to the synthesis of a 4-CF3 analogue of the anti-inflammatory drug celecoxib.

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