Direct synthesis of highly strained bifunctionalized 2H-thiete 1,1-dioxides

Abstract

Highly strained bifunctionalized dialkyl 2H-thiete-2,3-dicarboxylate 1,1-dioxides are directly synthesized from readily available sulfonyl chlorides and dialkyl acetylenedicarboxylates via the pyridine-mediated [2 + 2] annulation. In the annulation, pyridine first eliminates HCl from sulfonyl chlorides to generate sulfenes and then nucleophilically attacks the sulfenes to form zwitterionic intermediates, which nucleophilically attack dialkyl acetylenedicarboxylates followed by an intramolecular cyclization and isomerization to produce the final dialkyl 2H-thiete-2,3-dicarboxylate 1,1-dioxides. Pyridine serves as both base and nucleophilic catalyst. The current method is an efficient strategy for direct synthesis of highly strained bifunctionalized 2H-thiete 1,1-dioxide derivatives from readily available starting materials.