Photocatalytic Multisite Functionalization of Unactivated Terminal Alkenes by Merging Polar Cycloaddition and Radical Ring-Opening Process.

Although highly appealing for rapid access of molecular complexity, multi-functionalization of alkenes that allows incorporation of more than two functional groups remains a prominent challenge. Herein, we report a novel strategy that merges dipolar cycloaddition with photoredox promoted radical ring-opening remote C(sp)-H functionalization, thus enabling a smooth 1,2,5-trifunctionalization of unactivated alkenes. A highly regioselective [3+2] cycloaddition anchors a reaction trigger onto alkene substrates. The subsequent halogen atom transfer (XAT) selectively initiates ring-opening process, which is followed by a series of 1,5-hydrogen atom transfer (1,5-HAT) and intermolecular fluorine atom transfer (FAT) events. With this method, site-selective introduction of three different functional groups is accomplished and a broad spectrum of valuable β-hydroxyl-ϵ-fluoro-nitrile products are synthesized from readily available terminal alkenes.