Visible-Light-Assisted Chemoselective Hydrogenation of Arylalkenes and Arylalkynes Using Water as the Hydrogen Source.

The hydrogenation of arylalkenes and arylalkynes has been achieved using water, triphenylphosphine, and iodine under blue-light irradiation. The corresponding alkanes were obtained in good to excellent yields under mild conditions. Furthermore, the method demonstrates high chemoselectivity, tolerating aryl and nonbenzylic alkyl iodides. The reaction is proposed to proceed via polar hydroiodination followed by phosphine radical cation-mediated deiodination. A halogen bonding complex formed between triphenylphosphine and iodine plays a pivotal role in the process by generating the key triphenylphosphine radical cation upon blue-light irradiation.