Transition metal catalyzed C=C bond aziridination and C-H bond amination reactions are powerful synthetic methods for forming C-N bonds directly from unfunctionalized hydrocarbons, and have enormous synthetic potential in chemical processes leading to natural products, pharmaceuticals and materials. Catalytic C-H bond amination also offers a way to achieve functionalization with clean and environmentally sustainable atom efficiency.
This work will focus on olefin aziridinations and C-H bond aminations catalyzed by transition metal complexes. We employed N3-tripod scorpionate ligands to support different transition metal centers. Therefore, complexes [(L)M(NCCH3)3](BF4)n (L = tris{3,5-dimethylpyrazol-1-yl}methane, TpmMe,Me, M = Mn, Fe, Co, Ni, n = 2; L = tris{3-phenylpyrazol-1-yl}methane, TpmPh, M = Mn, Fe, Co, Ni, n = 2; L = hydrotris{3,5-dimethylpyrazol-1-yl}borate, TpMe,Me, M = Fe, Co, Ni, n = 1; L = hydrotris{3-phenyl-5-methylpyrazol-1-yl}borate, TpPh,Me, M = Mn, Co, Fe, Ni, n = 1) were prepared and characterized. These complexes were utilized as metal catalysts for nitrene transfer from phenyl-N-tosyliminoiodinane (i.e., PhI=NTs) to variety of organic substrates, resulting in olefin aziridination and C-H bond amination with varying degrees of efficiency. A wide range of organic products was obtained and fully characterized, and reaction mechanisms were probed with Hammett and kinetic isotope effects. Meanwhile, a masked Lewis acid [Fe(NCMe)6](BF4)2 was found to catalyze [2+1+2] and [3+2] cycloaddition reactions, leading to the formation of various five-membered nitrogen-containing compounds.