Four-component radical-polar crossover cyclization involving double insertion of SO2 to β-sulfonyl sultines

Sulfur oxides are widespread and gaining increasing attention in pharmaceutical and biotechnology discoveries owing to their heightened activities, despite the fact that sulfur dioxide (SO2) is one of the most harmful gaseous air pollutants. Considerable research efforts have been devoted to dealing with sulfur oxides in a greener and sustainable way. Herein, we report a visible-light-promoted four-component radical-polar crossover tandem cyclization involving twofold insertion of SO2 and the formation of S(IV) and S(VI) centers in one procedure. Various types of functionalized beta-sulfonyl sultines were afforded from easy-to-access C(sp(2))-H and C(sp(3))-H building blocks with high group compatibility under mild and operationally simple conditions. Gram-scale preparation and late-stage transformations demonstrate opportunities to rapidly construct molecular complexity. Mechanistic studies supported a SO2 bi-inserted radical-polar crossover cyclization relay sequence, which allows for a more efficient utilization of SO2 and is also more environmentally friendly.