Chiral arylideneaminoimidazolidin-4-ones: green synthesis and isomerisation mechanism in solution

Abstract

A green and eco-friendly synthetic approach of pure 2,5-disubstituted 3-arylideneaminoimidazolidin-4-ones is developed using water as the solvent. These new chiral arylideneaminoimidazolidin-4-one derivatives were obtained diastereoselectively in high overall yields and with high atom economy via the cyclocondensation of various aromatic aldehydes and α-amino acid hydrazides. Solid state studies were complemented by the behavior in solution investigated by NMR experiments and DFT quantum chemical calculations. The transformation from the kinetic arylideneaminoimidazolidin-4-one to the thermodynamic form is explained by a ring opening mechanism and by kinetic observations highlighting the important role played by the electronic richness of the substituents.