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Highly Diastereoselective Lithiation and Substitution of an ( S )‐Prolinyl Thiocarbamate via Sterically Homogeneous Lithio(thiocarbamate): Synthesis of Enantiomerically Pure Prolinethiols
Author(s) -
Sonawane Ravindra P.,
MückLichtenfeld Christian,
Fröhlich Roland,
Bergander Klaus,
Hoppe Dieter
Publication year - 2007
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200601853
Subject(s) - thiocarbamate , steric effects , chemistry , substitution reaction , electrophilic substitution , substitution (logic) , electrophile , lithium (medication) , alkyl , stereochemistry , medicinal chemistry , organic chemistry , catalysis , medicine , computer science , programming language , endocrinology
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.