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Relevant academic research and scientific papers

A highly efficient Cu catalyst system for the radical reactions of α-bromocarbonyls

In this communication, we established highly efficient Cu-catalyzed ARGET-ATRS (atom-transfer radical substitution) of alpha-bromocarbonyls with styrenes to produce tert-alkylated styrenes. The maximum TON was up to 12 000. Hünig's base was very important to regenerate active CuI. Moreover, a Cu-catalyzed C-C cleavage reaction via SH2′ and intermolecular C-H cyclization of α-bromoimide was found.

Organo-photoredox-catalyzed atom-transfer radical substitution of alkenes with α-carbonyl alkyl halides

A light-driven atom-transfer radical substitution (ATRS) and carboesterification reaction of alkenes with alkyl halides has been developed using PTH as the organo-photoredox catalyst. Two types of products were obtained, depending on the additive and solvent used during the reaction. Primary, secondary, and tertiary alkyl halides reacted to give the ATRS products. This protocol has several advantages: it requires mild reaction conditions and a low catalyst loading and exhibits a broad substrate scope and good functional group tolerance. Mechanistic studies indicate that alkyl radicals might be generated as the key intermediates via photocatalysis, providing a new direction for ATRS reactions.

Ruthenium-Catalyzed Heck-Type Alkenylation of Alkyl Bromides

The complex [CpRuCl(PPh3)2] displays a high catalytic activity for the Heck-type alkenylation of alkyl bromides in the first example using this metal under thermal conditions. The coupling reaction proceeds efficiently with a variety of functionalized tertiary, secondary, and primary alkyl bromides. The presence of Hünig's base has been revealed to be crucial for this transformation. Preliminary mechanistic studies support the participation of alkyl radicals in the reaction.

Copper-catalysed direct radical alkenylation of alkyl bromides

A copper-catalysed direct radical alkenylation of various benzyl bromides and α-carbonyl alkyl bromides has been developed. Compared with the recent radical alkenylations which mostly focused on secondary or tertiary alkyl halides, this transformation shows good reactivity to primary alkyl halides and tertiary, secondary alkyl halides were also tolerated. The key initiation step of this transformation is a copper-induced single-electron reduction of C-Br bonds to generate alkyl radical species. This journal is the Partner Organisations 2014.

Visible-light photocatalytic radical alkenylation of a-carbonyl alkyl bromides and benzyl bromides

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 acarbonyl alkyl bromides and benzyl bromides to furnish a-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 b-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 CBr bonds to generate alkyl radical species promoted by photocatalysts. The following carboncarbon bond-forming step involves a radical addition step rather than a metal-mediated process, thereby avoiding the undesired b-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 b-hydrides under mild conditions.

Nickel-catalyzed heck-type alkenylation of secondary and tertiary α-carbonyl alkyl bromides

Ni made it! A novel Heck-type reaction of secondary and tertiary α-carbonyl alkyl bromides, most likely involving a radical process, was achieved through the use of a nickel catalyst. Various substituted styrenes and 1,1-diaryl alkenes were utilized as substrates to easily construct α-alkenyl carbonyl compounds with tertiary or quaternary carbon centers. A catalytic cycle involving NiI/NiII is proposed based on our experimental results. EWG=electron-withdrawing group.