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Asymmetric Synthesis of Planar Chiral (Arene)tricarbonylchromium Complexes via Enantioselective Deprotonation by Conformationally Constrained Chiral Lithium‐Amide Bases
Author(s) -
Pache Sandrine,
Botuha Candice,
Franz Roberto,
Kündig E. Peter,
Einhorn Jacques
Publication year - 2000
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/1522-2675(20000906)83:9<2436::aid-hlca2436>3.0.co;2-n
Subject(s) - chemistry , enantioselective synthesis , lithium amide , benzaldehyde , amide , deprotonation , aldehyde , electrophile , stereochemistry , enantiomer , lithium (medication) , planar chirality , organic chemistry , catalysis , medicine , ion , endocrinology
Enantioselective lithiation/electrophile addition reactions with eight chiral Li‐amide bases, 1 – 8 , and five [Cr(arene)(CO) 3 ] complexes, 9 – 13 , were investigated. Restriction of conformational freedom in the chiral Li‐amide base Li‐ 1 , in general, did not result in an increase in asymmetric induction. A new route to enantiomerically enriched (75 – 92%) planar chiral ortho ‐substituted benzaldehyde complexes via enantioselective lithiation of benzaldimine complexes 16 and 17 is reported. Within the (1 S )‐enantiomer series of o ‐substituted benzaldehyde complexes 18a – d , the sign of the specific rotation, [ α ], is found to be positive, except for the trimethylstannyl derivative 18b . This is interpreted in terms of a reversed conformation of the aldehyde group.