NHC-Copper(I) Halide-Catalyzed Direct Alkynylation of Trifluoromethyl Ketones on Water
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AbstractAn efficient and easily scalable NHC-copper(I) halide-catalyzed addition of terminal alkynes to 1,1,1-trifluoromethyl ketones, carried out on water for the first time, is reported. A series of addition reactions were performed with as little as 0.1-2.0mol% of [(NHC)CuX] (X=Cl, Br, I, OAc, OTf) complexes, providing tertiary propargylic trifluoromethyl alcohols in high yields and with excellent chemoselectivity from a broad range of aryl- and more challenging alkyl-substituted trifluoromethyl ketones (TFMKs). DFT calculations were performed to rationalize the correlation between the yield of catalytic alkynylation and the sterics of N-heterocyclic carbenes (NHCs), expressed as buried volume (%VBur), indicating that steric effects dominate the yield of the reaction. Additional DFT calculations shed some light on the differential reactivity of [(NHC)CuX] complexes in the alkynylation of TFMKs. The first enantioselective version of a direct alkynylation in the presence of C1-symmetric NHC-copper(I) complexes is also presented. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
CitationCzerwiński P, Molga E, Cavallo L, Poater A, Michalak M (2016) NHC-Copper(I) Halide-Catalyzed Direct Alkynylation of Trifluoromethyl Ketones on Water. Chem Eur J 22: 8089–8094. Available: http://dx.doi.org/10.1002/chem.201601581.
SponsorsThe authors are grateful to Polish Ministry of Science and Higher Education for financial support of the research (grant Iuventus Plus IP2012 064172). A.P. thanks the Spanish MINECO for project CTQ2014-59832-JIN, and L.C. funding from King Abdullah University of Science and Technology (KAUST). We would like to thank Prof. Samir Zard (Ecole Polytechnique) for helpful discussion concerning the synthesis of trifluoromethyl ketones and Dr. P. Kwiatkowski and Dr. W. Chaladaj for a generous gift of samples of trifluoromethyl ketones and alkynes.
JournalChemistry - A European Journal
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