title: Formation of 2-Cyano-2-siloxyvinylallenes via Cyanide-Induced Brook Rearrangement in γ-Bromo-α,β,γ,δ-unsaturated Acylsilanes.
abstract: Reactions of γ-bromo-α,β,γ,δ-unsaturated acylsilanes with KCN under phase-transfer catalyst conditions using n-Bu4NBr afforded 2-cyano-2-siloxyvinylallenes via a tandem process that involves a nucleophilic attack of a cyanide ion and a Brook rearrangement induced conjugate vinylic 1,4-elimination. Use of a chiral cyanide ion source, derived from KCN and quaternary ammonium bromide derived from cinchona alkaloids, provided nonracemic allene derivatives. Based on this result and the reaction using a chiral hydride ion source, we propose a reaction pathway in which a Brook rearrangement mediated vinylic conjugate 1,4-elimination occurs in a syn alignment between the C-Br bond and C-Si bond in the silicate intermediate.
authors.forename: Masafumi
authors.initials: M
authors.lastname: Ando
authors.forename: Michiko
authors.initials: M
authors.lastname: Sasaki
authors.forename: Izumi
authors.initials: I
authors.lastname: Miyashita
authors.forename: Kei
authors.initials: K
authors.lastname: Takeda