Electrochemically cooperative halogen-cation delivery enables modular electrophilic haloesterification of both activated and unactivated alkenes

Abstract

Intermolecular haloesterification of alkenes is a practical platform for modular ester synthesis. However, current methods are restricted to aryl-activated and directing-group-containing alkenes, leaving low-reactivity, electron-deficient alkenes with alkyl substituents largely underexplored. Notably, electrophilic reactions involving chloroesterification of electron-deficient alkenes are also challenging due to the difficulty in controlling selectivity. In this work, we present an electrochemically cooperative halogen-cation delivery strategy that achieves modular electrophilic haloesterification of both activated and unactivated alkenes with good chemo-, regio-, and diastereoselectivity levels. It exhibits enhanced reactivity (with yields of up to 90%) and selectivity (regioselectivities and diastereoselectivities exceeding 20 : 1), as the amide mediates the transfer of Cl⁺ to the alkene, enabling the formation of stable halogen-containing cationic intermediates (β-halo carbocation or halonium) in the electrochemically oxidative ‘electrophile–nucleophile’ (‘E–Nu’) approach. Di-, tri-, and tetrasubstituted alkenes displaying various electronic properties, as well as terminal alkenes, have been successfully haloesterified, showcasing the good tolerance of the strategy to the presence of functional groups. Moreover, the strategy is applicable to gram-scale synthesis and late-stage elaboration of bioactive compounds. It also enables the construction of quaternary carbons, even multiple contiguous ones, in reactions.