Reactive iron carbonyl reagents via reaction of metal alkoxides with Fe(CO) < inf > 5 < /inf > or Fe < inf > 2 < /inf > (CO) < inf > 9 < /inf > : Synthesis of cyclobutenediones via double carbonylation of alkynes

Abstract

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 °C in THF to give 1,2-cyclobutenediones in 70-93% yields after CuCl 2· 2H 2O 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/Me 3NO. The Fe 2(CO) 9/t-BuOK reagent system also converts the alkynes to corresponding cyclobutenediones in 63-90% yields under similar reaction conditions. © 2010 American Chemical Society.