A Redox-Active Nickel Complex that Acts as an Electron Mediator in Photochemical Giese Reactions

We report a simple protocol for the photochemical Giese addition of C(sp³ )-centered radicals to a variety of electron-poor olefins. The chemistry does not require external photoredox catalysts. Instead, it harnesses the excited-state reactivity of 4-alkyl-1,4-dihydropyridines (4-alkyl-DHPs) to generate alkyl radicals. Crucial for reactivity is the use of a catalytic amount of Ni(bpy)₃ ²⁺ (bpy=2,2'-bipyridyl), which acts as an electron mediator to facilitate the redox processes involving fleeting and highly reactive intermediates.