Transition Metal-Catalyzed C-H Functionalization for Sustainable Syntheses of Alkenes and Heterocycles

Abstract

The rapid progress of C–H functionalization chemistry over the last decade has provided numerous efficient protocols for forming new chemical bonds. Especially, the ruthenium(II)-catalyzed direct C–H alkenylations and annulations have been proven viable with a broad substrates scope and excellent chemo-, regio-, and site-selectivity. These carboxylate-assisted ruthenium(II)-catalyzed C–H functionalizations were even allowed in an aerobic fashion with Cu(OAc)2•H2O under an atmosphere of ambient air. Yet, less expensive first-row transition metal complexes such as cobalt salts were also identified as versatile catalysts for step-economical chelation-assisted direct C−H alkenylations in user-friendly solvent. This Co(OAc)2 catalyst can enable the transformation smoothly with a widely range functional groups tolerance, to furnish the isoindolin-1-ones in high yields. In the last project, we developed silver-mediated alkyne annulations by C–H/P–H functionalizations. This transformation proceeded with excellent chemo- and site-selectivities in the presence of silver acetate as the terminal oxidant, thereby furnishing substituted phosphindole with broad scope. The radical mechanism of the C–H/C–P functionalization was unraveled though detailed mechanistic studies.