Cyclometalated (NNC)Ru(ii) complex catalyzed β-methylation of alcohols using methanol

Indolyl fragment containing phenanthroline based new ligands and their corresponding Ru(ii) complexes were synthesized and fully characterized by various spectroscopic techniques. The catalytic activity of these newly synthesized cyclometalated (NNC)Ru(ii) complexes was explored towards the beta-methylation of alcohols using methanol. Notably, these complexes displayed superior reactivity compared to various (NNN)Ru(ii) complexes. Utilizing this strategy, a wide range of primary, secondary, and aliphatic straight chain alcohols were selectively methylated. This protocol was further employed for the methylation of a few natural products and the gram scale synthesis of beta-methylated alcohols. A series of control experiments and kinetic studies were performed to understand the plausible reaction mechanism.

Automated summary

In this study, new ligands containing an indolyl fragment and phenanthroline, as well as their corresponding Ru(ii) complexes, were synthesized and characterized. The catalytic activity of these cyclometalated (NNC)Ru(ii) complexes towards the beta-methylation of alcohols using methanol as the reagent was investigated. The results showed that these complexes exhibited superior reactivity compared to various (NNN)Ru(ii) complexes. They selectively methylated a wide range of primary, secondary, and aliphatic straight chain alcohols. This methodology was also applied to the methylation of natural products and the gram scale synthesis of beta-methylated alcohols.