Isolation and stereochemistry of optically active selenonium imides

Optical resolution of racemic diaryl selenonium-N-toluene-4'-sulfonimides ( rac-1a-d) by liquid chromatography using an optically active column yielded optically pure selenonium imides. The absolute configuration around the se lenium atom of (-)-2,4,6-tri-tert-butyldiphenylselenon N-toluene-4'-sulfoni mide [(-)-1a] was determined to be S by X-ray crystallographic analysis, an d those of the other optically active selenonium imides were determined on the basis of their specific rotations and CD spectra. The kinetics of racem ization by pyramidal inversion of the optically active selenonium imides ()- and (-)-1b and 1d were studied. The results indicated that the activatio n energy for the racemization of optically active selenoniun. imides was gr eater than those for sulfonium imides.