Metalloradical activation of carbonyl azides for enantioselective radical aziridination

The carbonyl azide TrocN(3) (2,2,2-trichloroethoxycarbonyl azide) is a potent nitrogen radical precursor for radical olefin aziridination via Co(II)-based metalloradical catalysis (MRC). The cobalt(II) complex of D-2-symmetric chiral amidoporphyrin 3,5-Di(t)Bu-QingPhyrin proves to be an efficient catalyst that can activate TrocN(3) at room temperature to aziridinate various styrene derivatives, providing chiral N-carbonyl aziridines in high yields with excellent enantioselectivities. The new Co(II)-based catalytic system can even enable asymmetric aziridination of electron-deficient alkenes, such as methyl and ethyl acrylates. In addition to facile removal of Troc group for generation of unprotected aziridines, the resulting N-Troc-aziridines can be effectively opened by different types of nucleophiles to afford a series of chiral amine derivatives with excellent stereospecificity. Several lines of computational and experimental evidence support the underlying stepwise radical mechanism for Co(II)-catalyzed olefin aziridination. This represents the first example of asymmetric intermolecular olefin aziridination that employs carbonyl azides as the nitrogen source.

Automated summary

TrocN(3) serves as a potent nitrogen radical precursor for radical olefin aziridination catalyzed by a new Co(II)-based catalytic system, with the cobalt(II) complex of a D-2-symmetric chiral amidoporphyrin proving to be an efficient catalyst. This represents the first example of asymmetric intermolecular olefin aziridination using carbonyl azides as the nitrogen source, allowing for the enantioselective synthesis of various chiral amine derivatives.