Activation of alcohols as sulfonium salts in the photocatalytic hetero-difunctionalization of alkenes

Motifs related to 1,2-diols and 1,2-amino alcohols are found widely in bioactive natural products, drugs and agrochemicals. These highly sought-after substructures would ideally be constructed by the direct addition of alcohols to the C=C bond of alkenes, both common substrate classes in chemical synthesis. However, their direct union is only possible if one of the pair can be rendered electron-deficient through derivatization; such approaches typically require stoichiometric amounts of strong oxidants and often lack generality. Here we describe a straightforward process in which both simple and complex alcohols can be converted under photocatalytic conditions to the corresponding alkoxy radicals-via the formation of alkoxy sulfonium salts-that react with alkenes en route to 1,2-diol and 1,2-amino-alcohol derivatives. The method can be easily adapted from laboratory to industrial, kilogram scale using a photoflow system. Spectroscopic analysis and control experiments have been used to probe the underpinning mechanism.