title: Visible-light photocatalytic radical alkenylation of α-carbonyl alkyl bromides and benzyl bromides.
abstract: Through the use of [Ru(bpy)3Cl2] (bpy=2,2'-bipyridine) and [Ir(ppy)3] (ppy=phenylpyridine) as photocatalysts, we have achieved the first example of visible-light photocatalytic radical alkenylation of various α-carbonyl alkyl bromides and benzyl bromides to furnish α-vinyl carbonyls and allylbenzene derivatives, prominent structural elements of many bioactive molecules. Specifically, this transformation is regiospecific and can tolerate primary, secondary, and even tertiary alkyl halides that bear β-hydrides, which can be challenging with traditional palladium-catalyzed approaches. The key initiation step of this transformation is visible-light-induced single-electron reduction of C-Br bonds to generate alkyl radical species promoted by photocatalysts. The following carbon-carbon bond-forming step involves a radical addition step rather than a metal-mediated process, thereby avoiding the undesired β-hydride elimination side reaction. Moreover, we propose that the Ru and Ir photocatalysts play a dual role in the catalytic system: they absorb energy from the visible light to facilitate the reaction process and act as a medium of electron transfer to activate the alkyl halides more effectively. Overall, this photoredox catalysis method opens new synthetic opportunities for the efficient alkenylation of alkyl halides that contain β-hydrides under mild conditions.
authors: The College of Chemistry and Molecular Sciences, Wuhan University, 430072, Wuhan, Hubei, P.R. China.
authors: Qiang
authors: Q
authors: Liu
authors: Hong
authors: H
authors: Yi
authors: Jie
authors: J
authors: Liu
authors: Yuhong
authors: Y
authors: Yang
authors: Xu
authors: X
authors: Zhang
authors: Ziqi
authors: Z
authors: Zeng
authors: Aiwen
authors: A
authors: Lei