Synthesis and characterization of the first examples of ferrocene and [η5-CpCo(η4-C4Ph4)] derived 2-pyridones

Reactions of ferrocene and (η5-cyclopentadienyl)(η4-tetraphenylcyclobutadiene)cobalt derived alkynylaldehydes with p-anisidine gave the corresponding metal sandwich based alkynylimines, 4-methoxy-N-(3-ferrocenylprop-2-ynylidene)aniline and 4-methoxy-N-[3-(η5-cyclopentadienyl)(η4-tetra-phenylcyclobutadiene)cobalt prop-2-ynylidene]aniline. The 1,4-nucleophilic addition of sodium methylmalonate with these alkynylimines gave the first examples of metal sandwich substituted 2-pyridones, [methyl 1-(4-methoxyphenyl)-2-oxo-4-ferrocenyl 1,2-dihydropyridine-3-carboxylate and methyl 1-(4-methoxyphenyl) 2-oxo-4-(η5-cyclopentadienyl)(η4-tetra-phenylcyclobutadiene)cobalt 1,2-dihydropyridine-3-carboxylate in good yields. Reaction of sodium ethylmalonate with the ferrocene derived alkylimine gave the stable ferrocene derived 2-pyridone, ethyl 1-(4-methoxyphenyl)-2-oxo-4-ferrocenyl 1,2-dihydropyridine-3-carboxylate which was also structurally characterized.