Reactive Iron Carbonyl Reagents via Reaction of Metal Alkoxides with Fe(CO)5 or Fe2(CO)9: Synthesis of Cyclobutenediones via Double Carbonylation of Alkynes

Alkoxy bases such as t-BuOK react with Fe(CO)(5) to give reactive iron carbonyl intermediates that in turn react with alkynes at 70 degrees C in THF to give 1,2-cyclobutenediones in 70-93% Yields after CuCl2 center dot 2H(2)O oxidation. A novel 1,2-diacyloxyferrole derivative was isolated in the reaction of diphenylacetylene with Fe(CO)(5)/t-BuOK in the presence of acetyl chloride in contrast to the formation of a 1,4-diacyloxyferrole complex formed in the reaction using Fe(CO)(5)/Me3NO. The Fe-2(CO)(9)/t-BuOK reagent system also converts the alkynes to corresponding cyclobutenediones in 63-90% yields under similar reaction conditions.