Hydrogenative alkene perdeuteration aided by a transient cooperative ligand.

Deuterogenation of unsaturated organic compounds is an attractive route for installing C(sp 3 )-D bonds, but the existing methods typically use expensive D 2 and introduce only two deuterium atoms per unsaturation. Herein we report the hydrogenative perdeuteration of alkenes using readily available H 2 and D 2 O instead of D 2 , catalysed by an acridanide-based ruthenium pincer complex and resulting in the incorporation of up to 4.9 D atoms per C=C double bond in a single synthetic step. Importantly, adding a catalytic amount of thiol, which serves as a transient cooperative ligand, ensures the incorporation of deuterium rather than protium by balancing the rates of two sequential deuteration processes. The current method opens an avenue for installing perdeuteroalkyl groups at specific sites from widely available alkenes under mild conditions.