Synthesis of Heterocyclic‐Fused Furans and Dihydrofurans via (4+1)‐Annulation with Ylide: Exploration of Unique Reactivity Behavior of α‐Carbonyl Sulfoxonium Ylide.

A (4+1)‐annulation of arylidene heterocyclic‐N‐fused imidazolones with α‐carbonyl sulfoxonium ylides has been developed. The reaction enabled efficient access to a range of N‐heterocycle‐fused furans, such as secondary hydroxyl and the structural parts of drug/bioactive compounds. A unique triple‐role of α‐carbonyl sulfoxonium ylides and a characteristic stereo‐electronic functional behavior of the arylidene N‐fused imidazolones have been explored. [ABSTRACT FROM AUTHOR]