Electrophotochemical Radical Relay for Remote Alkenylation of Unactivated C(sp3)–H Sites in Alcohols

Abstract

The Mizoroki–Heck reaction is a powerful method for alkene formation from various molecules; however, its application has traditionally been limited to halogenated compounds. Accessing organic molecules with halogen atoms at specific positions in aliphatic systems is highly restricted, and their synthesis is extremely difficult. Therefore, achieving site-selective alkenylation of alkyl compounds at specific positions remains challenging. This paper presents a versatile redox-neutral method for the alkenylation of long-chain alkyl alcohols at unactivated δ-C(sp³)-H sites, enabling the construction of alkenols through electrophotochemical (EPC) cerium (Ce) catalysis with free alcohols. The method demonstrates excellent substrate compatibility, facilitating the use of both primary and secondary alcohols and enabling the successful synthesis of quaternary carbon alkenols. Mechanistically, cyclic voltammetry experiments reveal that the oxidative reaction is driven by electrochemical oxidation at the anode under applied potential. Additionally, styrene boronic acid remains unoxidized during the reaction, confirming a radical addition mechanism rather than a radical–radical coupling process. UV–vis experiments further demonstrate that the ligand not only activates the alkene boronic acid but also functions as a base to promote the ligand exchange between alcohol and Ce(IV)−Cl species.