Manganese-catalyzed regioselective C−H alkylation of indoles and benzo[h]quinoline with a variety of unactivated alkyl iodides is reported. Unlike other Mn-catalyzed C−H functionalization, this protocol does not require a Grignard reagent base and employs a simple and inexpensive MnBr 2 as a catalyst. This method tolerates diverse functionalities, including fluoro, chloro, bromo, iodo, alkenyl, alkynyl, pyrrolyl, and carbazolyl groups. The alkylation proceeds through a single-electron transfer pathway comprising reversible C−H manganesation and involving an alkyl radical intermediate.

Selective C(sp2)−H bond alkylation of indoline, carbazole and (2‐pyridinyl)arenes with unactivated alkyl bromides is achieved using MnBr2 catalyst in the absence of an external ligand. The alkylation uses a simple LiHMDS base and avoids the necessity of Grignard reagent, unlike other Mn‐catalyzed C−H functionalization. This reaction proceeded either through a five‐ or a less‐favored six‐membered metallacycle, and tolerated diverse functionalities, including alkenyl, alkynyl, silyl, aryl ether, pyrrolyl, indolyl, carbazolyl and alkyl bearing fatty alcohol and polycyclic‐steroid moieties. Alkylation follows a single electron transfer (SET) pathway involving 1e oxidative addition of alkyl bromide and a rate‐limiting C−H metalation.