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.