Highly diastereoselective lithiation and substitution of an (S)-prolinyl thiocarbamate via sterically homogeneous lithio(thiocarbamate): synthesis of enantiomerically pure prolinethiols.
Highly diastereoselective lithiation-substitution reactions of an (S)-proline derived S-alkyl thiocarbamate was accomplished. The configuration of the predominant alkyllithium species and the stereochemical course of the electrophilic substitution reactions are deduced by a combination of X-ray crystal structure analysis, NMR spectroscopic studies, deuteration/dedeuteration experiments, and quantum chemical calculations. The lithium intermediate (S,S)-9 was found to be kinetically and thermodynamically favoured, whereas (S,R)-9 rapidly epimerizes.
Sonawane
Ravindra P
RP
Organisch-Chemisches Institut, Westfälische Wilhelms-Universität Münster, Corrensstrasse 40, 48149 Münster, Germany.
Mück-Lichtenfeld
Christian
C
Fröhlich
Roland
R
Bergander
Klaus
K
Hoppe
Dieter
D