The Thiosulfinyl Group Serves as a Stereogenic Center and Shows Diamagnetic Anisotropy Similar to That of the Sulfinyl Group

The pseudotetrahedral geometry of the thiosulfinyl group (>SS) in the thionosulfite which was prepared by treatment of cis-3,4-di-tert-butylthiolane-3,4-diol with 1,1‘-thiobisbenzimidazole is stable enough to allow the isolation of two diastereomers. X-ray crystallographic analysis revealed that the configuration of the >SS group of the major diastereomer (45% isolated yield) is syn to the thiolane ring, while that of the minor diastereomer (10% isolated yield) is anti to the thiolane ring. 1H NMR spectrum analysis clarified that the shielding and deshielding zones of the >SS group are similar to those of the >SO group. Chemical properties of the >SS group toward thermolysis, hydrolysis, and oxidation were clarified. The absorptions or bands in the UV/vis, IR, and Raman spectra, which originate from the >SS group, were assigned on the basis of the B3LYP/6-31G* level calculations.