SYNTHESES AND PECULIAR BEHAVIOR IN SOLUTIONS OF OPTICALLY-ACTIVE TELLURONIUM SALTS

A diastereomeric (epimeric) mixture of ethylmethylphenyltelluronium (1 S)-(+)-camphor-10-sulfonate (dia.-1) was optically resolved by fractio nal recrystallization into the diastereomerically pure isomers (R)(Te) -1 and (S)(Te)-1. The absolute configurations of the isomers were dete rmined by the X-ray crystallographic analysis of (R)(Te)-1. Enantiomer ically pure (R)-ethylmethylphenyltelluronium perchlorate, tetrafluorob orate, p-chlorobenzenesulfonate, bornane-10-sulfonate, tetraphenylbora te, and picrylsulfonate (R)-2-7 were isolated, respectively, by anion- exchange reactions of diastereomerically pure(R)(Te)-1. The optically active telluronium salts were found to show peculiar optical propertie s on their specific rotations and circular dichroism spectra in soluti ons compared with those of the corresponding sulfonium and selenonium salts. On the basis of NMR studies, the behavior on the optical proper ties of the optically active telluronium salts was found to be caused by a strong solvation in polar solvents.