title: NHC-Copper(I) Halide-Catalyzed Direct Alkynylation of Trifluoromethyl Ketones on Water.
abstract: An 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 0.1-2.0 mol % 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.
authors.affiliation: Institute of Organic Chemistry, Polish Academy of Sciences, 01-224, Warsaw, Kasprzaka 44/52, Poland.
authors.forename: Paweł
authors.initials: P
authors.lastname: Czerwiński
authors.affiliation: Faculty of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664, Warsaw, Poland.
authors.forename: Edyta
authors.initials: E
authors.lastname: Molga
authors.affiliation: KAUST Catalysis Center, Physical Sciences and Engineering Division, King Abdullah University of Science and Technology, 23955-6900, Thuwal, Saudi Arabia. luigi.cavallo@kaust.edu.sa.
authors.forename: Luigi
authors.initials: L
authors.lastname: Cavallo
authors.affiliation: Institut de Química Computacional i Catàlisi and Departament de Química, Universitat de Girona, Campus Montilivi, 17071, Girona, Catalonia, Spain. albert.poater@udg.edu.
authors.forename: Albert
authors.identifier: 0000-0002-8997-2599
authors.initials: A
authors.lastname: Poater
authors.affiliation: Institute of Organic Chemistry, Polish Academy of Sciences, 01-224, Warsaw, Kasprzaka 44/52, Poland. michal.michalak@icho.edu.pl.
authors.forename: Michał
authors.initials: M
authors.lastname: Michalak
keywords: N-heterocyclic carbenes; alkynylation; copper; ketones; on water