Carbonylic-Carbon-Centered Mechanism for Catalytic α-Methylation

Abstract

The multicarbonyl manganese pincer complex-catalyzed α-methylation reaction is studied. In this theoretical work, an unprecedented carbonylic-carbon-centered mechanism is discovered. That is, the catalytic center is on the carbonyl ligand instead of the metal atom, such as the common aromatization/dearomatization metal–ligand cooperation mechanism. Further, the origins of chemoselectivity of enone hydrogenation are addressed with the $DEL-type NBO analyses. With a manganese pincer catalyst, the donor–acceptor electron transfer is found from the C═C bond to the C═O antibond, which can be regarded as the original driving force for the enone C═C hydrogenation. In contrast, the Noyori-type RuH2(diphosphine)(diamine) catalysts favor the C═O hydrogenation, where the driving force is the donor–acceptor interaction associated with the O···H–N hydrogen bond.