Cooperative Photo- and Cobalt-Catalyzed Transfer Hydrogenative Alkene Hydroacylation

Abstract

The transfer hydrogenative cross-coupling of primary alcohols and alkenes offers a streamlined and atom-economical approach to ketone synthesis, employing readily available alcohols as latent acyl equivalents and thereby avoiding the use of preactivated acylating reagents or discrete oxidation–reduction steps. Despite significant advances, existing methodologies are largely dominated by precious metal catalysis, often require elevated temperatures, and typically exhibit a strong bias toward nucleophilic alkenes, delivering branched ketone products with limited control over regioselectivity. These limitations underscore the need for complementary catalytic strategies that operate under milder conditions while expanding alkene scope and selectivity profiles. Herein, we report a dual photo- and cobalt-catalyzed transfer hydrogenative coupling of primary alcohols with alkenes, enabled by the synergistic combination of a decatungstate photocatalyst and a cobalt co-catalyst. This protocol proceeds efficiently under mild conditions and exhibits a distinct preference for electrophilic alkenes, providing linear aryl alkyl ketones with excellent regioselectivity. The transformation accommodates a wide range of aryl methanols and alkenes, demonstrating broad substrate scope and high functional group tolerance. Notably, it is readily scalable without loss of efficiency, underscoring the practicality of the transformation. Moreover, the protocol proves directly applicable to the late-stage modification of complex molecules, facilitating the concise synthesis of pharmaceutically relevant ketones and derivatives of natural products such as ibuprofen analogs and fragrance components. Preliminary mechanistic studies suggest that photoexcited decatungstate promotes hydrogen atom abstraction from aryl methanols, generating benzylic radicals that are further oxidized to aldehyde intermediates in cooperation with the cobalt catalyst. Subsequent hydrogen atom transfer (HAT)-initiated radical addition to electrophilic alkenes affords carbon–carbon bond formation with high linear selectivity. The cobalt catalyst is proposed to play a key role in mediating hydrogen transfer events and facilitating catalyst turnover. This dual-catalytic strategy thus provides an operationally simple platform for regioselective ketone synthesis from abundant feedstocks.

Keywords

Photocatalysis / Cobalt / Hydrogen transfer / Alkene hydroacylation / Benzyl alcohol / Activated alkene / Styrene / Aldehyde

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