Investigation of active sites for C–H functionalization on carbon-based catalyst: Effect of nitrogen-containing functional groups and radicals

Transition metal catalyzed carbon-carbon bond formation reactions have become important transformations in organic synthesis. In this study, we have explored a general strategy of transition metal free carbocatalytic carbon–hydrogen (C–H) functionalization. A carbon-based catalyst bearing nitrogen functional groups can facilitate the C–H functionalization of unactivated arenes to obtain biaryl products. We propose the active sites on the catalyst by analyzing its chemical composition before and after reaction, in-situ FT-IR, in-situ electron spin resonance (ESR), and density function theory calculation. As a result, stable NH groups and radicals were found to be effective for the reaction, providing high recyclability of the catalyst. The present methodology offers a diverse substrate scope without any dry or inert conditions, thus opening the door for an alternative to the conventional metal-based coupling reactions.