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Visible-Light Photocatalytic Radical Alkenylation of α-Carbonyl Alkyl Bromides and Benzyl Bromides

Authors

  • Dr. Qiang Liu,

    1. The College of Chemistry and Molecular Sciences, Wuhan University, 430072, Wuhan, Hubei (P.R. China), Fax: (+86) 27-68754672
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    • These authors contributed equally to this work.

  • Hong Yi,

    1. The College of Chemistry and Molecular Sciences, Wuhan University, 430072, Wuhan, Hubei (P.R. China), Fax: (+86) 27-68754672
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    • These authors contributed equally to this work.

  • Jie Liu,

    1. The College of Chemistry and Molecular Sciences, Wuhan University, 430072, Wuhan, Hubei (P.R. China), Fax: (+86) 27-68754672
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  • Yuhong Yang,

    1. The College of Chemistry and Molecular Sciences, Wuhan University, 430072, Wuhan, Hubei (P.R. China), Fax: (+86) 27-68754672
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  • Xu Zhang,

    1. The College of Chemistry and Molecular Sciences, Wuhan University, 430072, Wuhan, Hubei (P.R. China), Fax: (+86) 27-68754672
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  • Ziqi Zeng,

    1. The College of Chemistry and Molecular Sciences, Wuhan University, 430072, Wuhan, Hubei (P.R. China), Fax: (+86) 27-68754672
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  • Prof. Aiwen Lei

    Corresponding author
    1. The College of Chemistry and Molecular Sciences, Wuhan University, 430072, Wuhan, Hubei (P.R. China), Fax: (+86) 27-68754672
    2. Beijing National Laboratory for Molecule Sciences (BNLMS), Key Laboratory for Molecular Recognition and Function, Institute of Chemistry, the Chinese Academy of Sciences, 100191, Beijing (P.R. China)
    • The College of Chemistry and Molecular Sciences, Wuhan University, 430072, Wuhan, Hubei (P.R. China), Fax: (+86) 27-68754672
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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[BOND]Br bonds to generate alkyl radical species promoted by photocatalysts. The following carbon[BOND]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.

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