Bifunctional Sodium Dithionite Promoted Radical-Polar Crossover Cyclization: Diversified Synthesis of Functionalized Cyclic Sultines

A catalyst-free reductive radical-polar crossover cyclization with alkenes and sodium dithionite to construct densely functionalized cyclic sultines was described. The key to the success of this practical protocol relies not only on a bifunctional role of sodium dithionite, that is, serving as radical initiator and SO2 source, but also on the diversified conversions (RPCC/SO2 insertion/SN2 cyclization and RPCC/SO2 insertion/1,4-addition cyclization processes), which enabled efficient construction of target compounds with the high efficiency and atom- and step-economy under mild conditions.