N-(2,3,5,6-Tetrafluoropyridyl)sulfoximines: synthesis, X-ray crystallography, and halogen bonding

Abstract

In the presence of KOH, NH-sulfoximines react with pentafluoropyridine to give N-(tetrafluoropyridyl)sulfoximines (NTFP-sulfoximines) in moderate to excellent yields. Either a solution-based or a superior solvent-free mechanochemical protocol can be followed. X-Ray diffraction analyses of 26 products provided insight into the bond parameters and conformational rigidity of the molecular scaffold. In solid-state structures, sulfoximines with halo substituents on the S-bound arene are intermolecularly linked by C–X⋯OS (X = Cl, Br) halogen bonds. Hirshfeld surface analysis is used to assess the type of non-covalent contacts present in molecules. For mixtures of three different S-pyridyl-substituted NTFP-sulfoximines and N-iodosuccinimide (NIS) in CDCl₃, association constants were determined by ¹H NMR spectroscopy. The data revealed a dependence of the halogen bond strength on the position of the pyridyl nitrogen indicating the presence of N–I⋯N(S-pyridyl) interactions. Neither the SO oxygen nor the tetrafluoropyridyl-substituted nitrogen of the sulfoximine appeared to be involved in halogen bonding.