Terminal Selective Arylation of Inert Alkanes via Radical-Organometallic Crossover.

Selectivity is an essential part of organic synthesis and key to synthetic efficiency, where it can help reduce energy requirements for product separation, purification, and disposal of low value by-products. However, selectivity is challenging to achieve in hydrocarbon molecules, with C─H functionalization of alkanes almost invariably leading to a complex mixture of products favoring branched isomers and linear selectivity remaining elusive. Herein we report a mild and direct method that combines photo-hydrogen atom transfer (photo-HAT) and nickel catalyzed organometallic chainwalking chemistry to give the first highly linear selective arylation reaction starting from inert alkanes. Key to success is crossover from a radical to organometallic chainwalking mechanism permitted by a monodentate lutidine ligand, allowing an unselective photo-HAT step to be funneled regioconvergently to form the linear arylation product for a variety of alkanes. This result is in sharp contrast to the unselective formation of branched products using bidentate ligands and demonstrates monodentate heterocycles to be a privileged ligand class for selective C─H functionalization. Preliminary mechanistic experiments are consistent with the radical-organometallic crossover mechanism and support it as an important step toward controllable and selective functionalization of simple hydrocarbons.