190960-75-9

Upstream product

• 3975-77-7 1-bromo-2,4,6-tri-tert-butylbenzene 
• 190960-75-9 2,4,6-tri-tert-butylphenyl mesityl telluroxide 
• 92720-46-2 dimesityl ditelluride 

Relevant academic research and scientific papers

Synthesis and stereochemistry of chiral selenoxides and telluroxides

Optically pure selenoxides stabilized by bulky substituents and/or intramolecular coordination with amino group were isolated by optical resolution of a diastereomeric mixture of selenoxide and chromatographic separation of a racemic mixture of selenoxide using an optically active column. Optically pure telluroxides stabilized by similar techniques were also isolated by chromatographic resolution. The absolute configu-rations were determined by X-ray crystallographic analysis and circular dichroism spectra. Kinetic studies on the racemization of these chiral chalcogen oxides were examined, and a mechanism for the racemization via achiral hydrate was proposed based on the H2 18O tracer studies.

Isolation of stable enantiomerically pure telluroxides and their stereochemistry

Optical resolution of kinetically and thermodynamically stabilized diaryl telluroxides possessing bulky substituents (rac-1a-d) and amino group (rac-2a-c), respectively, by liquid chromatography using optically active columns yielded stable enantiomerically pure telluroxides. The absolute configurations of the optically active telluroxides were determined by comparing their specific rotations and CD spectra with those of sulfur or selenium analogues. The kinetics for the racemization of optically active telluroxides in solution was studied, and it was found that kinetic and thermodynamic stabilization were very effective preventing the racemization of telluroxides. The stabilization energy of telluroxides by intramolecular coordination of the amino group to the tellurium atom was estimated to be ca. 5 kcal mol-1 by variable temperature 1H NMR measurement. The mechanism for the racemization of optically active telluroxides was studied by an isotope experiment using H218O, and the results indicated that optically active telluroxides underwent racemization via an achiral tetracoordinated hydrate.

First Isolation and Stereochemistry of Optically Active Telluroxides

Optically active telluroxides 1 and 2 were isolated for the first time by means of medium-pressure liquid chromatography using an optically active column. Absolute configuration of the telluroxides (+)-1 and (+)-2 was determined to be R based on their specific rotations and circular dichroism spectra. The configurational lability and mechanism for racemization via an achiral hydrate were clarified by kinetic study and isotope tracer experiment.