Apparent Gas-Phase Nucleophilic Aromatic Substitution Reactions of Dimethyl(phenyl)silyl Cations

Nucleophilic aromatic substitution (S_NAr) reactions are widely used and are of great utility in synthesis. In this article, we report an unexpected apparent gas phase S_NAr reaction between (4-substituted-phenyl)dimethylsilyl cations and their neutral counterparts. This type of reaction, where the dimethyl(phenyl)silyl cation donates a methide to an aryl ring, has not heretofore been observed in either the gas phase or in solution. The gas phase provides a window to intrinsic reactivity in the absence of solvent, so that inherent reactivity can be ferreted out. Calculations are used to interpret the activating ability of the silyl cation and to probe possible mechanistic pathways.