Photoinduced ruthenium-catalyzed alkyl-alkyl cross-coupling reactions

Abstract

C–H functionalization reactions constitute a key pillar in streamlining synthesis methods. In this context, the use of visible light to mediate metal-catalyzed C–H functionalization reactions is currently emerging as an important strategy to facilitate such transformations and enables mild C–H functionalization reactions at ambient conditions without the need for external photosensitizers or reactive reagents. Herein, we report on a photochemical approach that allows for C(sp3)–H functionalization reactions using simple [Ru(cymene)Cl2]2 and a phosphoric acid diester as catalysts. This strategy enables formal C(sp3)–C(sp3) coupling reactions to access valuable, sterically demanding amines and expands photochemical C–H functionalization reactions toward reaction pathways exclusive to photochemistry. Detailed mechanistic experiments and density functional theory calculations suggest the formation of a cyclometalated ruthenium complex that is stabilized by the phosphoric acid diester anion and serves as a catalyst for C–H functionalization reactions and single-electron transfer to access C–H functionalization reactions via a deprotonation-radical addition mechanism.