LAUSR

Inexpensive cobalt-catalyzed oxidative C-H functionalization has emerged as a powerful tool for the construction of C-C and C-Het bonds, which offers unique potential for transformative applications to modern organic synthesis. In the early stage, these transformations typically required stoichiometric and toxic transition metals as the sacrificial oxidants, thus the formation of metal-containing waste was inevitable. In contrast, naturally abundant molecular O 2 has more recently been successfully employed as a green oxidant in cobalt catalysis, thus, considerably improving the sustainability of such transformations. Recently, a significant monument was gained by the use of electricity as a sustainable and environmentally benign redox reagent in cobalt-catalyzed C-H functionalization, thereby, preventing the consumption of cost-intensive chemicals, while at the same time addressing the considerable safety hazard related to the use of molecular oxygen in combination with flammable organic solvents. Considering the unparalleled potential of the aforementioned approaches for sustainable green synthesis, this review summarizes the recent progress in cobalt-catalyzed oxidative C-H activation until early 2020.