Optical resolution and configurational stability of selenoxides stabilizedby intramolecular coordination

2-((Dimethylamino)methyl)phenyl alkyl (or aryl) selenoxides, configurationa lly stabilized by intramolecular coordination of an amino group to the sele nium atom, were optically resolved into their enantiomeric isomers by means of high-performance liquid chromatography using an optically active column packed with amylosecarbamate derivative/silica gel. This is the first exam ple of the isolation of optically pure selenoxides without bulky substituen ts and also the first isolation of optically pure alkyl aryl selenoxides. T he absolute configuration of the (-)-isomers could be assigned to be the S- form by comparison of their specific rotations, circular dichroism spectra, and behavior on the optically active column with those of the sulfur analo gue, prepared by Andersen's method. Racemization of the optically active se lenoxides was accelerated not only in acidic solution but also in basic med ia. This result indicates there are two different mechanisms for their race mization in acidic and basic media. The stabilization energy of the selenox ides by the intramolecular coordination of an amino group to the selenium a tom was estimated to be ca. 3 kcal mol(-1) on the basis of variable-tempera ture H-1 NMR, measurements.