Absolute configuration and racemization mechanism of arenechalcogenic acids: resolution of tellurinic acid

• Published in: Tetrahedron: asymmetry Vol. 15; no. 23; pp. 3791 - 3797
• Main Authors: Nakashima, Yusuke, Shimizu, Toshio, Hirabayashi, Kazunori, Yasui, Masanori, Nakazato, Masaki, Iwasaki, Fujiko, Kamigata, Nobumasa
• Format: Journal Article
• Language: English
• Published: OXFORD Elsevier Ltd 29.11.2004; Elsevier
• Subjects: Chemistry; Chemistry, Inorganic & Nuclear; Chemistry, Organic; Chemistry, Physical; Physical Sciences; Science & Technology; OXIDATION; SULFOXIDES; INITIO MO CALCULATIONS; OPTICAL RESOLUTION; MOLECULAR CALCULATIONS; EFFECTIVE CORE POTENTIALS; STEREOCHEMISTRY; SULFONIUM; ACTIVE SELENONIUM IMIDES; PYRAMIDAL INVERSION
• ISSN: 0957-4166; 1362-511X
• DOI: 10.1016/j.tetasy.2004.10.018

[Display omitted] An optically active arenetellurinic acid (+)- 1d was obtained by means of liquid chromatography on a chiral column. The absolute configuration of the optically active tellurinic acid was assigned by comparing its circular dichroism spectrum with that of an optically active sulfinic acid, the absolute configuration of which was determined by X-ray crystallographic analysis. The absolute configurations of areneseleninic acids, which were previously obtained by chromatographic resolution, were assigned also on the basis of their circular dichroism spectra. The optically active tellurinic acid ( S)-(+)- 1d was stable toward racemization in hexane, although the racemization occurred in hexane/2-propanol. Kinetic studies on the racemization, the oxygen exchange reaction using H 2 18O, and theoretical studies revealed that a pathway involving an achiral tellurane formed by the addition of water to tellurinic acid exists for the racemization. The racemization mechanism of the optically active seleninic acid involving a seleninate anion, which was proposed previously, was confirmed by experiments using H 2 18O. The racemization mechanism of the optically active sulfinic acid in solution was concluded to be the same as that of the optically active seleninic acid. The difference in the racemization mechanism among the optically active chalcogenic acids is due to their ability to form hypervalent hydrate structures.