NMR spectroscopic and computational analysis of E/Z isomerism in imines derived from isatin

Abstract

Isatin reacts with primary amines to yield mixtures of E and Z imine stereoisomers. This study provides a detailed structural analysis of selected isatin-derived imines using ¹H and ¹³C NMR spectroscopy, complemented by computational methods. The E/Z ratio in solution is shown to depend strongly on stabilization by solvent interactions and substituents attached to the imine nitrogen. Predominant isomer structures are typically stabilized by π-stacking between aromatic rings, highlighting the key role of non-covalent interactions in determining stereochemical products.