Flash Communication: Reactions of Borole with Michler’s Ketone Versus Thioketone

In this work, we interrogate the reactivity of pentaphenylborole with 4,4′-bis(dimethylamino)benzophenone (Michler’s ketone) and its heavier congener, bis(dimethylamino)thiobenzophenone (Michler’s thioketone). The ketone inserts the CO unit to generate an unsaturated BOC 5 heterocycle while the thioketone coordinates to the boron center but the adduct thermally isomerizes via migration of a C-Ph unit and insertion of the sulfur atom to furnish a BSC 3 boracycle with a pendent alkene.