title: Studies on the reactive species in fluoride-mediated carbon-carbon bond-forming reactions: carbanion formation by desilylation with fluoride and enolates.
abstract: The reactive species in fluoride-mediated carbon-carbon bond-forming reactions was investigated. The regio- and diastereoselectivities of silanes reacting with cyclohexenone in the presence of a catalytic amount of fluoride was compared to the reactivity of analogous solvent-separated lithium ion pairs. Closely analogous behavior was observed, showing that carbanions and not siliconate complexes are the reactive species in the fluoride-catalyzed reactions. Spectroscopic investigations unambiguously show that phenylthiobenzyl anion will form by reaction of silane with tris(dimethylamino)sulfonium difluorotrimethylsilicate (TASF) or crypt[2.1.1]-solvated lithium enolates. The catalytic cycle runs smoothly with the crypt[2.1.1] complex of alpha-(phenylthio)benzyllithium as the initiator and enolate as the carrier of the desilylation reaction.
authors.affiliation: Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706, USA.
authors.forename: Margaret M
authors.initials: MM
authors.lastname: Biddle
authors.forename: Hans J
authors.initials: HJ
authors.lastname: Reich