Double SO₂ Insertion into 1,7-Diynes Leading to Functionalized Naphtho[1,2‑<i>c</i>]thiophene 2,2-dioxides

A novel metal-free double SO2 insertion/multicomponent bicyclization cascade of benzene-linked 1,7-diynes has been established by treatment with aryldiazonium tetrafluoroborates and DABCO–bis­(sulfur dioxide) under redox-neutral conditions, providing a range of dual sulfone-containing naphtho­[1,2-c]­thiophene 2,2-dioxides with generally high stereoselectivity. The reaction pathway is proposed to proceed through the sequence of arylsulfonyl-radical-induced 6-exo-dig/5-endo-trig bicyclization, H-abstraction, and diazotization.