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. (C) 2018 Elsevier Inc. All rights reserved.