Electron-Transfer Photoredox Catalysis: Development of a Tin-Free Reductive Dehalogenation Reaction

作者：Jagan M. R. Narayanam, Joseph W. Tucker, Corey R. J. Stephenson · 发表于：Journal of the American Chemical Society · 年份：2009 · DOI：10.1021/ja9033582 · 被引用次数：991 · 研究领域：Radical Photochemical Reactions、Catalytic C–H Functionalization Methods、CO2 Reduction Techniques and Catalysts

We report an operationally simple, tin-free reductive dehalogenation system utilizing the well-known visible-light-activated photoredox catalyst Ru(bpy)(3)Cl(2) in combination with (i)Pr(2)NEt and HCO(2)H or Hantzsch ester as the hydrogen atom donor. Activated C-X bonds may be reduced in good yields with excellent functional-group tolerance and chemoselectivity over aryl and vinyl C-X bonds. The proposed mechanism involves visible-light excitation of the catalyst, which is reduced by the tertiary amine to produce the single-electron reducing agent Ru(bpy)(3)(+). A subsequent single-electron transfer generates the alkyl radical, which is quenched by abstraction of a hydrogen atom. Reductions can be accomplished on a preparative scale with as little as 0.05 mol % Ru catalyst.