Synthesis and dynamic stereochemistry of 4-aryl-thiomorpholine-3,5-dione derivatives

• Seven new N-aryl-substituted thiomorpholine-3,5-diones have been characterized by X-ray diffraction method.
• Five orto-substituted N-aryl thiomorpholine-3,5-diones exhibited restricted rotations around N-aryl bond.
• Temperature-depended NMR and quantum chemical calculations were applied for the estimation of the energy barriers.

A series of new N-aryl-substituted thiomorpholine-3,5-diones were synthesized. Crystal structures of seven compounds were established on the basis of X-ray crystallography. Stable at room temperature diastereomers were detected for (2-phenyl)-substituted derivatives using 1H NMR. The dynamic stereochemistry of compound 36 was studied with variable-temperature 1H NMR and the mechanism of diastereomers interconversion was proposed on the basis of quantum chemical calculations.