Iron(III)chloride oxidation of tricarbonyl(vinylketene)iron(0)-alkyne adducts

Oxidation of the adducts formed from tricarbonyl(vinylketene)iron(0) complexes and alkynes by iron(III) chloride in methanol/water leads to the replacement of the tricarbonyliron(0) unit with an oxygen atom derived from the water. This pathway to furan-3(2H)-ones requires the presence of an electron-withdrawing substituent on carbon-2 of the vinylketene–alkyne adduct. Data used to assign the structures of some of the vinylketene–alkyne adducts used in this study included an X-ray crystal structure analysis of the unusual lactone complex 5c.