Rapid Methylation of Aryl Bromides Using Air-Stable DABCO-Bis(Trimethylaluminum) via Nickel Metallaphotoredox Catalysis

Herein, we report the use of bis(trimethylaluminum)-1,4-diazabicyclo[2.2.2]octane (DABAl-Me₃) as practical source of radicals for the introduction of valuable methyl groups to aryl bromides via a Nickel/metallaphotocatalytic cross coupling strategy.

We report a metallaphotocatalytic strategy for the selective methylation of (hetero)aryl bromides via nickel-catalyzed cross-coupling with bis(trimethylaluminum)-1,4-diazabicyclo[2.2.2]octane (DABAl-Me₃), as a commercially available, air-stable, and non-pyrophoric aluminum-based reagent. The method enables a fast, robust, and scalable methylation protocol that broadly accommodates various functional groups while preventing protodehalogenation. Mechanistic studies confirm the unprecedented generation of methyl radicals from an organo-aluminum precursor under photoredox conditions, bypassing the limitations of conventional two-electron pathways. This work expands the toolbox of practical radical precursors and provides a streamlined approach for selective C(sp²)─CH₃ bond formation.