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Description
The ease of the unsaturated system reactivity proceeding via -silyl carbocation ion can be explained by the stabilizing effects of the silicon-carbon bond interaction with carbocation ion - known as -silicon effect. This can be achieved by either vertical (hyperconjugation) or non-vertical (formation of cyclic silonium ion) stabilization. The formation of the latter, in combination with other stabilizing effects, causes 1,2-silyl migration [1].
Previously, we have reported the use of Brønsted acid to catalyze reactions of propargyl silanes to form various silyl dienes and indenes [2,3]. Herein, we report the expanded use of the concept by using electrophilic bromine to induce the formation of the reactive allylic cation that readily reacts with a variety of nucleophilic solvents like methanol, dimethylformamide, and acetic acid to form allyl functionalized vinyl silanes.
Use and the functionality of the obtained vinyl silanes are showcased in a variety of transition metal-catalyzed transformations like Suzuki-Miyaura coupling, C-H activation, electrophilic silicon exchange reaction, and Lewis acid-promoted intramolecular cyclization to form indenes.
