Multicomponent Annulative SO2 Insertion of Heteroatom-Linked 1,7-Diynes for Accessing Tricyclic Sulfones

A metal-free radical multicomponent bicyclization of heteroatom-linked 1,7-diynes with aryl diazonium tetrafluoroborates and DABCO-bis(sulfurdioxide) (DABSO) is reported, enabling annulative SO2 insertion access to produce two types of skeletally diverse tricyclic sulfones, namely, thieno[3,4-c]quinoline 2,2-dioxides and thieno[3,4-c]chromene 2,2-dioxides, with moderate to good yields by simply tuning the linkers of the 1,7-diynes. This protocol demonstrates remarkable compatibility regarding N- and O-linked 1,7-diynes with different substitution patterns and aryl diazonium tetrafluoroborates.