Reactions of a series of bis(α-amino acidato)copper(ii) complexes with formaldehyde and benzamide: aldol-type condensation versus Mannich aminomethylation

Abstract

In the reactions of bis(α-amino acidato)copper(II) with formaldehyde and benzamide, competing processes occur and the preferred pathway depends on the nature and number of the α-carbon substituents of the chelated amino acid, and the pH of the reaction medium. Aldol-type condensation yields complexes with oxazolidine ring(s) while Mannich aminomethylation results in the formation of complexes with N-methylbenzamido pendant arm(s). The crystal structure determination of bis(3-methylbenzamido-5-methyloxazolidine-4-carboxylato)copper(II) dihydrate establishes its formation from a combination of both processes, in which aldol condensation occurs first. The chemistry of these reactions is rationalized with a proposed reaction scheme. The synthesized compounds are characterized by infrared spectroscopy and microanalysis.