A radical chain hydroarylation of alkenes enabled by triplet energy transfer using aryl iodides as aryl donor reagents was reported. The reaction is mild and green, displays high reaction efficiency, good functional group compatibility and substrate applicability, excellent anti-Markovnikov selectivity and could be easily scaled-up to gram scales. Alkynes and complex alkenes were amendable. The halogen-atom transfer (XAT) promoted by in-situ generated silyl radical is crucial for the transformation. The application of the reaction in the synthesis of pharmceutiacally-relavant tetrahydroquinoline scaffold has been also demonstrated via rational design of the substrate. When the reaction occurs intramolecularly, relatively inert aryl bromide could serve as aryl donor. Meanwhile, the feasibility of phenyl xanthate as alternative aryl donor reagent was also preliminarily probed.

Key words: triplet energy transfer, halogen-atom transfer, hydroarylation of alkenes, radical chain reaction, anti-Markovnikov addition