Copper-nitrenoid formation and transfer in catalytic olefin aziridination utilizing chelating 2-pyridylsulfonyl moieties

We have developed an efficient protocol for copper-catalyzed olefin aziridination using 5-methyl-2-pyridinesulfonamide or 2-pyridinesulfonyl azide as the nitrenoid source. The presence of a 2-pyridyl group significantly facilitates aziridination, suggesting that the reaction is driven by the favorable formation of a pyridyl-coordinated nitrenoid intermediate. Using this chelation-assisted strategy, synthetically acceptable yields of aziridines could be obtained with a range of aryl olefins even in the absence of external ligands. Importantly, a large excess of olefin is not required. X-ray crystallography, ESI-MS, Hammett plot analysis, kinetic studies, and computational undertakings strongly support that the observed aziridination is driven by internal coordination.