title: Redox mediators in visible light photocatalysis: photocatalytic radical thiol-ene additions.
abstract: Synthetically useful radical thiol-ene reactions can be initiated by visible light irradiation in the presence of transition metal polypyridyl photocatalysts. The success of this method relies upon the use of p-toluidine as an essential additive. Using these conditions, high-yielding thiol-ene reactions of cysteine-containing biomolecules can be accomplished using biocompatibile wavelengths of visible light, under aqueous conditions, and with the thiol component as the limiting reagent. We present evidence that p-toluidine serves as a redox mediator that is capable of catalyzing the otherwise inefficient photooxidation of thiols to the key thiyl radical intermediate. Thus, we show that co-catalytic oxidants can be important in the design of synthetic reactions involving visible light photoredox catalysis.
authors.affiliation: Department of Chemistry, University of Wisconsin-Madison , 1101 University Avenue, Madison, Wisconsin 53706, United States.
authors.forename: Elizabeth L
authors.initials: EL
authors.lastname: Tyson
authors.forename: Zachary L
authors.initials: ZL
authors.lastname: Niemeyer
authors.forename: Tehshik P
authors.initials: TP
authors.lastname: Yoon
mesh_terms: D000475:Alkenes / Q000737:chemistry*; D002384:Catalysis; D008027:Light; D010084:Oxidation-Reduction; D055668:Photochemical Processes; D011725:Pyridines / Q000737:chemistry*; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D014052:Toluidines / Q000737:chemistry*; D028561:Transition Elements / Q000737:chemistry*
chemical_list: D000475:Alkenes; D011725:Pyridines; D013438:Sulfhydryl Compounds; D014052:Toluidines; D028561:Transition Elements; C029370:4-toluidine