Mn(OAc) 3 -Promoted Sulfonation- ipso -Cyclization Cascade via the SO 3 - Radical: The Synthesis of Spirocyclic Sulfonates.

A radical sulfonation- ipso -cyclization cascade promoted by Mn(OAc) 3 ·2H 2 O using functionalized alkynes or alkenes and potassium metabisulfite (K 2 S 2 O 5 ) is reported. A total of 30 spirocyclic sulfonates were synthesized under mild conditions. We also demonstrate a modular synthesis approach in multiple steps for the preparation of various azaspiro[4,5]-trienone-based sulfonamides and sulfonate esters.