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Enantioselective Lithiation and Substitution of ( E )‐Cinnamyl N , N ‐Diisopropylcarbamate through Use of (−)‐Sparteine Complexes
Author(s) -
Behrens Karin,
Fröhlich Roland,
Meyer Oliver,
Hoppe Dieter
Publication year - 1998
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/(sici)1099-0690(199811)1998:11<2397::aid-ejoc2397>3.0.co;2-2
Subject(s) - chemistry , sparteine , carbanion , enantioselective synthesis , carboxylation , acylation , diastereomer , toluene , epimer , stereochemistry , substitution reaction , lithium (medication) , medicinal chemistry , silylation , iodide , chirality (physics) , electrophilic substitution , organic chemistry , catalysis , medicine , nambu–jona lasinio model , chiral symmetry breaking , physics , quantum mechanics , quark , endocrinology
The title reaction leads to diastereomeric lithium carbanion pairs that are configurationally unstable and equilibrate even at temperatures below –50 °C. The initially formed epimer (1 S )‐ epi ‐ 10 is rapidly converted to the thermodynamically more stable (1 R )‐ 10 (in toluene solution). Carboxylation, acylation with acid chlorides, stannylation, and silylation take place at the α‐position with stereoinversion (79‐86% ee ). Methylating agents attack the γ‐position; here, the stereochemical course depends on the leaving group, anti ‐S E′ for the iodide (50% ee ) and syn ‐S E′ (48% ee ) for the tosylate.