Synthesis, isolation, and characterization of two stereoisomeric ring sulfoxides of thioridazine

A selective oxidation of thioridazine to give exclusively its ring sulfoxides and a separation of the resulting products as diastereoisomeric pairs of enantiomers (DL, LD and DD, LL) are reported. These pairs were characterized by TLC, high-performance liquid chromatographic, IR, UV, 1H-NMR, 13C-NMR, GC-MS, and elemental analyses, and by reduction to thioridazine by lithium aluminum hydride. Structural data for the separated diastereoisomeric pairs or their nitric acid salts were obtained from NMR and IR studies. Gram quantities of each of the two diastereoisomeric pairs of enantiomers were isolated in better than 99% purity.