Room-Temperature C–H Bond Functionalization by Merging Cobalt and Photoredox Catalysis

A non-noble metal-free protocol has been developed for C–H bond functionalization at room temperature by merging cobalt-mediated catalysis with photocatalysis. The reaction requires only oxygen as sole oxidant and operated at room temperature under redox-neutral conditions. Visible-light activated photoredox catalyst functions as an electron transfer reagent with oxygen as a terminal oxidant in the cobalt-mediated C–H and N–H bond annulation. The developed methodology allows annulations with various coupling partners. The concept demonstrated herein is expected to enhance the scope of cobalt catalysis as applied to sustainable fine chemical synthesis.