Unveiling the Selectivity of Ru(II)-Catalyzed C-H Activation for Defluorinative Cyclization of 2-Arylbenzimidazole and Trifluoromethyl Diazo: A DFT Study.

The synthesis of monofluorinated heterocyclic compounds by C-H activation combined with defluorination is useful. Studies on the reaction mechanism and selectivity have shown that these processes play a positive role in promoting the development of monofluorinated reactions. Density functional theory (DFT) calculations were performed to investigate the mechanism and selectivity of Ru(II)-catalyzed 2-arylbenzimidazole with trifluoromethyl diazo. DFT calculations showed that C-H activation occurs through a concerted metalation/deprotonation (CMD) mechanism. After that, deprotonation and defluorinative cyclization are assisted by acetate and trifluoroethanol (TFE). Further mechanistic insights through noncovalent interaction (NCI) analysis were also obtained to elucidate the origin of the selectivity in the defluorination process.