Mechanistic studies of copper-catalyzed alkene aziridination

The mechanism of the copper-catalyzed aziridination of alkenes using [N-(p- toluenesulfonyl)imino]-phenyliodinane (PhINTs) as the nitrene source has be en elucidated by a combination of hybrid density functional theory calculat ions (B3LYP) and kinetic experiments. The calculations could assign a Cu(I) /Cu(III)-cycle to the reaction and demonstrate why a higher oxidation state of copper cannot catalyze the reaction. A mechanism whereby Cu(II)-catalys t precursors can enter the Cu(I)/Cu(III)-cycle is suggested. Three low-ener gy pathways were found for the formation of aziridines, where the two new N -C bonds are formed either in a nonradical concerted or consecutive fashion , by involvement of singlet or tripler biradicals. A close correspondence w as found between the title reaction and the Jacobsen epoxidation reaction i n terms of spin;crossings and the mechanism for formation of cis/trans isom erized products. The kinetic part of the study showed that the reaction is zero order in alkene and that the rate-determining step is the formation of a metallanitrene species.