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.