Dehydrogenative Annulation of Silylated 1 H -Indoles with Alkynes via Silyl Migration.

We investigated the dehydrogenative annulation of silylated 1 H -indole derivatives with alkynes to synthesize a silole-fused indole. The addition of the in situ generated silylium ion to alkynes was followed by the sila-Friedel-Crafts reaction via silyl migration, realizing regioselective dehydrogenative annulation controlled by the steric bulkiness of a base. The optical properties of the obtained siloloindoles indicated fluorescence of which the intensity depends on the location of the fused silole.