Regioselectivity in intermolecular Pauson-Khand reactions of dissymmetric fluorinated alkynes
Jean-Claude Kizirian1, Nuria Aiguabella, Albert Pesquer
1Unitat de Recerca en Síntesi Asimètrica (URSA-PCB), Institute for Research in Biomedicine (IRB) and Departament de Química Orgànica, Universitat de Barcelona, c/Baldiri Reixac, 10, E-0 8028 Barcelona, Spain. jean-claude.kizirian@univ-tours.fr
Abstract:
Stoichiometric and catalytic intermolecular Pauson-Khand reactions (PKRs) of dissymmetric fluorinated alkynes were performed, affording regioselectively α-fluorinated cyclopentenones. Ethyl 4,4,4-trifluorobutynoate was an excellent substrate; its reaction with norbornadiene gave the corresponding PKR adduct in good yield and complete regioselectivity. Conjugate addition of nitroalkanes or cyanide to this adduct is stereospecific and entails concomitant loss of a trifluoromethyl group. This reaction can be exploited to prepare cyclopentenones featuring quaternary centers.
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