The dichotomous behavior of allylsilanes in the additions to platinum α,β-unsaturated carbenes.

The observation of allylsilane dual reactivity with α,β-unsaturated platinum carbenes is described. The reaction pathways are controlled by the nature of the catalytic conditions. Under nonpolar conditions, a (3 + 2) cycloaddition is favored to provide decorated tricyclic indole and benzofuran products. Alternatively, the application of Lewis basic solvents enables the formation of C2-allylated indoles and benzofurans. An array of heterocyclic products are afforded in good yields, and the process illustrates the distinct and dichotomous reactivity of allylsilanes. The mechanistically divergent outcomes can be attributed to solvent effects on the respective intermediate stabilizations.