Enhanced Three-Component Chloro-/Azido-Fluoroalkylation of Unactivated Alkenes via the Proximity Effect in a Heterogenous Metallaphotocatalyst

Heterogeneous metallaphotocatalytic chemical transformations employing a recyclable catalyst are highly desirable for organic synthesis. However, the rational design and controlled preparation of well-defined, site-isolated metal/photo bifunctional heterogeneous catalysts to achieve this goal remain a significant challenge. In this study, we demonstrate the covalent attachment of a homogeneous molecular MnSalen complex (where Salen = N,N′-bis(salicylidene)ethylenediamine) onto the surface of graphitic carbon nitride (CN) via an amide bond for visible-light-driven chloro- and azido-fluoroalkylation of unactivated alkenes. The amide covalent linkage between MnSalen and CN not only facilitates electron delocalization and enhances the light-harvesting capabilities of the CN photosensitizer but also exerts a proximity effect that markedly enhances the ability of the Mn sites to capture alkyl radical intermediates during the reaction process. A diverse set of unactivated alkenes could be efficiently chloro- and azido-fluoroalkylated to their corresponding difunctionalized products in moderate to high yields with good functional group compatibility. Furthermore, the practicability of the heterogeneous protocol is illustrated through the late-stage diversification of various bioactive compounds and pharmaceuticals. Notably, this integrated photocatalyst demonstrates high stability and can be recycled at least 10 times without loss of activity and selectivity.