The determination of sulfoxide configuration in five-membered rings using NMR spectroscopy and DFT calculations

Abstract

Cyclic five-membered ring sulfoxides and sulfones were prepared by a stepwise in situ oxidation of the corresponding sulfides with meta-chloroperbenzoic acid in an NMR tube. The oxidation was followed by NMR and both 1H and 13C NMR data were collected. The geometries of all of the compounds were optimized using the DFT B3LYP/6-31G ∗∗ method and the 13C and 1H chemical shifts were calculated for geometry-optimized structures with the DFT B3LYP/6-31++G ∗∗ method. The calculated 13C chemical shifts induced by oxidation (Δ δ values) were in very good agreement with the experimental data and could be used to determine the oxidation state of the sulfur atom (–S–, –SO–, –SO 2–). The characteristic differences of the induced oxidation chemical shifts of the carbon atoms in the α-position and β-position to sulfur were successfully used to distinguish between the diastereoisomeric sulfoxides and allowed configuration determination.