Eosin-Mediated Alkylsulfonyl Cyanation of Olefins.

Eosin-Y (EY)-mediated alkylsulfonyl cyanation of olefins was shown to afford alkylsulfonyl nitriles in good yields. On the basis of transient absorption spectroscopy, the reaction was shown to proceed via photoinduced electron transfer from EY* to an O-cyanated derivative of the photocatalyst, formed in situ, with generation of the corresponding sulfinate that is oxidized by EY into a sulfonyl radical. Addition of the latter on the olefin, followed by a radical cyano group transfer, then furnished the nitrile along with a RSO radical sustaining the radical chain.