Aromatic C-H addition of ketones to imines enabled by manganese catalysis

Selectivity control of varied C-H bonds in a complex molecule is a long-standing goal and still a great challenge in C-H activation field. Most often, such selectivity is achieved by the innate reactivity of different C-H bonds. In this context, the classic Mannich reaction of acetophenone derivatives and imines is ascribed to the more reactive C(sp³)-H bonds α to the carbonyl, with the much less reactive aromatic C(sp²)-H bonds remaining intact. Herein we report an aromatic C(sp²)-H addition of ketones to imines enabled by manganese catalysis, which totally reverses the innate reactivity of C-H bonds α to the carbonyl and those on the aromatic ring. Diverse products of ortho-C-H aminoalkylated ketones, cyclized exo-olefinic isoindolines, and three-component methylated isoindolines can be successfully accessed under mild reaction conditions, which significantly expands the synthetic utilities of ketones as simple bulk chemicals.