The earliest application of photoredox catalysis to Reductive dehalogenation were limited by narrow substrate scope or competing reductive coupling.
Unactivated carbon-iodine bonds can be reduced using the strongly reducing photocatalyst tris-(2,2’-phenylpyridine)iridium (Ir(ppy)). The increased reduction potential of Ir(ppy) compared to [Ru(bipy)] allows direct reduction of the carbon-iodine bond without interacting with a stoichiometric reductant. Thus, the iridium complex transfers an electron to the substrate, causing fragmentation of the substrate and oxidizing the catalyst to the Ir(IV) oxidation state. The oxidized photocatalyst is returned to its original oxidation state by oxidising a reaction additives.
Like tin-mediated radical dehalogenation reactions, photocatalytic reductive dehalogenation can be used to initiate cascade cyclizations