Syntheses of Z‑Iodovinylfurans and 2‑Acyl Furans via Controllable Cyclization of Ynenones

A divergent synthesis of Z-iodovinylfurans and 2-acyl furans promoted by NIS via controllable cyclization of ynenones is reported. The reaction proceeded by sequential 5-exo-dig electrophilic cyclization to intermediate 2-(iodomethylene)-2H-furanium cation D, providing a range of synthetically valuable and useful trisubstituted furan derivatives 2 and 3 in moderate to excellent yields. This approach is metal-free, mild, and atom-economic, with good selectivity and high stereoselectivity.