Highly enantioselective reactions of configurationally labile epimeric diamine complexes of lithiated S-benzyl thiocarbamates.
Substitution reactions that employ primary-carbamoyl-protected arylmethanethiols are described. The enantiodetermining step was found to occur in the post-deprotonation step as a dynamic thermodynamic resolution with a chiral bis(oxazoline) ligand. The configurationally labile lithium complexes were trapped with various electrophiles to yield different substitution products in good to excellent yields and enantiomeric excesses. The absolute configurations of the substitution products were determined, and the stereochemical pathway of the substitution reaction was elucidated for different classes of electrophiles. The temperature-dependent epimerization process was monitored by 1H and 6Li NMR spectroscopy.
Lange
Heiko
H
Organisch-Chemisches Institut der Universität, Westpfälische Wilhelms-Universität Münster, Corrensstr. 40, 48149 Münster, Germany.
Bergander
Klaus
K
Fröhlich
Roland
R
Kehr
Seda
S
Nakamura
Shuichi
S
Shibata
Norio
N
Toru
Takeshi
T
Hoppe
Dieter
D