Reaction of ferrocenylcarbene complexes of Cr, Mo and W with alkynes: synthesis of ferrocenylcyclobutenones, ferrocenylfurans and ferrocenylketoesters

Ferrocenylcarbene complexes of Cr, Mo and W react with alkynes to produce cyclobutenones, furans and/or ketoesters. The reaction is quite sensitive to the substituents of the alkyne, regardless of the identity of the metal. Cyclobutenones are formed only in the reactions of diphenylacetylene, a rare occurrence for metal carbene complexes. Ketoesters are secondary reaction products and result from oxidation of furan derivatives during the course of the reaction and/or silica-gel chromatography.