title: Role of fluoride in accelerating the reactions of dialkylstannylene acetals.
abstract: The most common method for achieving the regioselective monoalkylation of diols involves formation of dialkylstannylene acetals as intermediates. Reactions of dialkylstannylene acetals with alkyl halides are slow, but rates are enhanced by addition of fluoride or other nucleophiles. The mechanism of the fluoride-accelerated alkylation of dialkylstannylene acetals was studied at several levels of theory in the gas phase, in N,N-dimethylformamide (DMF) solution, and in DMF solution in the presence of tetramethylammonium ions. The reactive species were adducts involving addition of fluoride to tin. Under the conditions that most closely simulated experiment, reactions from fluoridated monomers and monofluoridated dimers were calculated to have similar activation energies. In the transition states in the rate-determining steps for the two pathways, carbon-oxygen bond formation was between 60 and 75% complete while tin-oxygen bond cleavage was much less advanced, between 6 and 16% complete. A test of Sn-O bond dissociation indicated that the "Sn-O bond cleavage first" mechanism is not a minimum energy pathway.
authors: Department of Chemistry, Dalhousie University, 6274 Coburg Road, P.O. Box 15000, Halifax, Nova Scotia, Canada B3H 4R2.
authors: Simiao
authors: S
authors: Lu
authors: Department of Chemistry, Dalhousie University, 6274 Coburg Road, P.O. Box 15000, Halifax, Nova Scotia, Canada B3H 4R2.
authors: Russell J
authors: RJ
authors: Boyd
authors: Department of Chemistry, Dalhousie University, 6274 Coburg Road, P.O. Box 15000, Halifax, Nova Scotia, Canada B3H 4R2.
authors: T Bruce
authors: TB
authors: Grindley