Asymmetric radical cyclopropanation of alkenes

Metalloradical catalysis (MRC), which utilizes metal-centered radicals to homolytically activate substrates for catalytic generation of metal-stabilized organic radicals as key intermediates, has emerged as a conceptually new approach for controlling both reactivity and stereoselectivity of radical reactions. As the first application of MRC, Co(II) complexes of chiral porphyrins, as stable 15e-metalloradicals, have been demonstrated as effective catalysts for asymmetric cyclopropanation of alkenes with diazo compounds via a stepwise radical mechanism.