The Ylide Dance: Base-Induced Furan Synthesis via Formal [3+2] Annulation of Phenacyl- and Alkenyl Sulfonium Salts

A methodology for the synthesis of substituted furans via an "ylide dance" sequence has been developed. The reaction involves phenacyl sulfonium salts and alkenyl- or propargyl sulfonium salts under basic conditions. The key feature is a stepwise evolution where a primary sulfur ylide, generated from phenacyl sulfonium salt and base, transforms into another ylide, which then undergoes conversion into yet another, a "third generation" ylide, culminating in the formation of the target furan.