Ion-Cyclotron Resonance Studies of Alkylsilyl Ions. I. The Reactions Between Alcohols and the Trimethylsilyl Cation

Abstract

Nucleophilic attack of an alcohol (ROH) at the electrophilic silicon centre of the trimethylsilyl cation (Me3Si+) produces the 1 : 1 adduct Me3-O+(H)R(1). The adduct may fragment by loss of methane to yield Me2Si+-O-R; and this elimination is most pronounced when R = Me. When R ≥ C2H5, the major decomposition pathway of (1) involves elimination of the alkene [R-H] to produce Me3Si-O+H2, which may undergo further reaction with the neutral alcohol to reform (1). The proton transfer which accompanies the elimination of [R- H] from (1) originates predominantly from C2 of the alcohol; this suggests the intermediacy of a four-membered transition state in this reaction.