Regioselective Multicomponent Sulfonylation/Cyclization of Unactivated Alkenes to Access Sulfonylated Six- and Seven-Membered Cyclic Enamines via SO2 Insertion.

Radical cascade cyclization of alkenes involving the insertion of sulfur dioxide has proven to be a promising tool to access sulfonylnated heterocycle compounds, whereas cyclization of unactivated alkenes has been much less explored. Here, we developed a three-component cascade of unactive alkenes with sulfur dioxide and aryldiazonium tetrafluoroborates to generate sulfonylated tetrahydropyridines and azepines via the cleavage of alkenyl C-H bonds. Moreover, this protocol exhibited excellent chemical and regioselectivity and compatibility with broad functional groups.