Visible-light photocatalytic radical alkenylation of α-carbonyl alkyl bromides and benzyl bromides.
Chemistry
; 19(16): 5120-6, 2013 Apr 15.
Article
em En
| MEDLINE
| ID: mdl-23426910
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 ß-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 ß-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 ß-hydrides under mild conditions.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Idioma:
En
Revista:
Chemistry
Assunto da revista:
QUIMICA
Ano de publicação:
2013
Tipo de documento:
Article