Resolution and determination of the absolute configuration of the enantiomers of a trans-alpha-disulfoxide

The trans isomer of 2,7-di-tert-butylnaphtho[1,8-cd][1,2]dithiole 1,2-dioxide, a vic-disulfoxide of the highest thermal stability reported to date, has been resolved into its enantiomers by preparative chiral liquid chromatography. This represents the first resolution achieved of a vic-disulfoxide. The absolute configuration of the isolated enantiomers has been determined to be (+)-(S,S), (-)-(R,R) from a comparison of experimental and calculated ECD and VCD spectra. The long-wavelength ECD band at about 330 nm had a positive sign in the (+)-(S,S)-form and a negative sign in the (-)-(R,R)-enantiomer. A photocatalyzed slow decrease in optical activity was observed in solution, most likely due to racemization by homolytic (O)S-S(O) bond cleavage and bissulfinyl radical recombination.