Toshio Shimizu

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 selenium atom of (−)-2,4,6-tri-tert-butyldiphenylselenonium N-toluene-4‘-sulfonimide [(−)-1a] was determined to be S by X-ray crystallographic analysis, and those of the other optically active selenonium imides were determined on the basis of their specific rotations and CD spectra. The kinetics of racemization by pyramidal inversion of the optically active selenonium imides (+)- and (−)-1b and 1d were studied. The results indicated that the activation energy for the racemization of optically active selenonium imides was greater than those for sulfonium imides.

Synthesis and Reactions of 1,2-Dithiete and Related Compounds

Bis(methoxycarbonyl)-1,2-dithiete 1, the cyclic dimer 2, and the tetramer 3 were obtained by oxidation of titanocene dithiolene complex with sulfuryl chloride, and the crystal structures of 1 and 2 were determined by X-ray crystallographic analysis. Novel ring conversion reaction among the compounds was found under various conditions, such as in non-polar solvent, in polar solvent, and in the presence of silica-gel.

Synthesis And Stereochemistry Of Optically Active Telluronium Salts

Enantiomerically pure telluronium salts (R)-2-7 were isolated by optical resolution of a diastereomeric ethylmethylphenyltelluronium (1S)-(+)-camphor-10-sulfonate (dia.-1) followed by subsequent anion exchange reactions. Absolute configuration of the salts was determined based on X-ray crystallographic analysis. The optically active telluronium salts were found to show peculiar optical properties on their specific rotations and circular dichroism spectra in solutions.

Reactions of Pentafluorobenzenesulfonyl Chloride with Alkenes in the Presence of a Ruthenium or Palladium Complex

The reactions of pentafluorobenzenesulfonyl chloride with styrenes in the presence of a ruthenium(II) phosphine complex and subsequent treatment with triethylamine were found to give (E)-1-aryl-2-(pentafluorobenzenesulfonyl)ethene in high yields. On the other hand, palladium catalyzed reactions of pentafluorobenzenesulfonyl chloride with styrenes in the presence of a base afforded modest yields of both (E)-1-aryl-2-(pentafluorophenyl)ethene and (E)-1-aryl-2-(pentafluorobenzenesulfonyl)ethene.