Alkene 1,3‐Difluorination via Transient Oxonium Intermediates

Abstract The 1,3‐difunctionalization of unactivated alkenes is an under‐explored transformation that leads to moieties that are otherwise challenging to prepare. Herein, we report a hypervalent iodine‐mediated 1,3‐difluorination of homoallylic (aryl) ethers to give unreported 1,3‐difluoro‐4‐oxy groups with moderate to excellent diastereoselectivity. The transformation proceeds through a different mode of reactivity for 1,3‐difunctionalization, in which a regioselective addition of fluoride opens a transiently formed oxonium intermediate to rearrange an alkyl chain. The optimized protocol is scalable and shown to proceed well with a variety of functional groups and substitution on the alkenyl chain, hence providing ready access to this fluorinated, conformationally controlled moiety.