A Ring‐Expansion Methodology Involving Multicomponent Reactions: Highly Efficient Access to Polysubstituted Furan‐Fused 1,4‐Thiazepine Derivatives

Tri-ed and tested: Ring expansion processes were observed in the novel three-component reaction of thiazolium salts 1, 1,1-disubstituted ketenes 2 (generated in situ), and activated alkynes (see scheme, EWG=electron-withdrawing group). This protocol allows highly efficient assembly of unique furan-fused 1,4-thiazepine derivatives from simple and readily accessible starting materials.