Manganese-Catalyzed Redox-Neutral C-H Olefination of Ketones with Unactivated Alkenes.

Since 1987, stoichiometric cyclomanganation of ketones and subsequent reactions with olefins in the presence of either palladium salts or trimethylamine N-oxide (Me3 N+ O- ) have been reported, but the catalytic versions remain untouched so far. Herein, the first manganese-catalyzed redox-neutral C-H olefination of ketones with unactivated alkenes is described, and shows a distinct reactivity with its parent stoichimetric reactions. Remarkably, mechanistic experiments and DFT calculations uncovers a unique concerted bis-metalation deprotonation (CBMD) mechanism of the Mn-Zn-enabled C-H bond activation.