A Diruthenium Catalyst for Selective, Intramolecular Allylic C-H Amination: Reaction Development and Mechanistic Insight Gained through Experiment and Theory

The mixed-valent paddlewheel complex tetrakis-(2-oxypyridinato)diruthenium(II,III) chloride, [Ru-2(hp)(4)Cl], catalyzes intramolecular allylic C-H amination with bis-(homoallylic) sulfamate esters. These results stand in marked contrast to reactions performed with dirhodium catalysts, which favor aziridine products. The following discussion constitutes the first report of C-H amination using complexes such as [Ru-2(hp)(4)Cl] and related diruthenium adducts. Computational and experimental studies implicate a mechanism for [Ru-2(hp)(4)Cl]-promoted C-H amination involving hydrogen-atom abstraction/radical recombination and the intermediacy of a discrete, albeit short-lived, diradical species. The collective data offer a coherent model for understanding the preference of this catalyst to oxidize allylic (and benzylic) C-H bonds.