Formation of Anionic Trifunctionalized Metallalactones by Nucleophilic Addition at the β-Carbonyl of a Pyruvoyl Ligand

Anionic nucleophilic reagents Nu- = CH3O-, C2H5O-, t-BuO-, CH3S-, and P(C6H5)2- were
found to react with (CO)4Fe(CO2CH3)[C(O)C(O)CH3] to afford two isomers of anionic
trifunctionalized metallalactones, whose formation resulted from an addition of the nucleophile to the β carbonyl of the pyruvoyl ligand. In
this reaction, the metallacycle formation was found to occur by a further addition of the
oxygen of the same β carbonyl on a terminal carbonyl. In acidic medium, these anionic
complexes evolved into neutral metallalactones already
obtained by performing the same reaction with pronucleophiles (Nu-H type reagents).
Achievement of when the reaction was performed with t-BuO-
could result from an intermediate formation of the enolate form of the pyruvoyl ligand [Fe]C(O)-C(CH2)-O- under basic conditions.