An Unusual Perpendicular Metallacycle Intermediate is the Origin of Branch Selectivity in the Rh(II)-Catalyzed C-H Alkylation of Aryl Sulfonamides with Vinylsilanes

The rhodium(II)-catalyzed, branch-selective C-H alkylation of aryl sulfonamides with vinylsilanes was recently developed by our group, and the unique reactivity and selectivity of the reaction was extensively studied using density functional theory (DFT) calculations. A detailed computational study of the experimentally confirmed reaction intermediates permitted us to understand the nature of dirhodium complexes, and the findings indicated that a strained perpendicular metallacycle is formed, which disfavors the development of linear-selective migratory insertion transition states.