Radical-Induced Decarboxylation/Cyclization of Benzoyl Peroxides with 1,8-Enynes through In Situ SO ₂ Insertion/Smiles Rearrangement Relay Strategy

A metal-free multicomponent reaction involving readily available 1,8-enynes, benzoyl peroxide, and DABCO·(SO₂)₂ has been successfully developed. The desired products, sulfonylated indolo[2,1-a]isoquinoline derivatives, were obtained without the need for any catalysts or additives. In addition, this strategy utilizes readily available benzoyl peroxide as an aryl radical precursor, enabling the transformation through a sequential in situ SO₂ insertion/Smiles rearrangement/radical cyclization relay process. Moreover, the transformation process is highly economical, facilitating the formation of multiple chemical bonds, including one C-N bond, two C-C bonds, and two C-S bonds in a single radical initiation.