Access to axially chiral styrenes via a photoinduced asymmetric radical reaction involving a sulfur dioxide insertion

The wide applicability in various fields enables development of novel methods to access axially chiral styrenes to be of significance. Among the developed and potential synthetic strategies for this type of framework, the route based on an asymmetric radical process is more challenging and has not been achieved so far. Here we report a photo-promoted, three-component, asymmetric free radical reaction of potassium alkyltrifluoroborates, potassium metabisulfite, and 1-alkynylnaphthalen-2-ols, delivering axially chiral (S, E)-1-(1-(alkylsulfonyl)-2-vinyl)naphthalen-2-ols with excellent enantioselectivity (93%–99% enantiomeric excess) and good yield (up to 97%). The transformation involves in situ generation of alkylsulfonyl radicals, tandem enantioselective radical addition, and a reduction process of radical species.