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Asymmetric Coordination Chemistry by Chiral-Auxiliary-Mediated Dynamic Resolution under Thermodynamic Control.
MedLine Citation:
PMID:  21254425     Owner:  NLM     Status:  In-Data-Review    
Abstract/OtherAbstract:
A method is presented for the asymmetric synthesis of chiral ruthenium polypyridyl complexes that starts from racemic cis-[Ru(pp)(2) Cl(2) ] (pp=2,2'-bipyridine or 1,10-phenanthroline ligands). The chiral bidentate ligands (R)-2-(isopropylsulfinyl)phenol, (R)-SO, and preferably the more electron-rich derivative (R)-2-(isopropylsulfinyl)-4-methoxyphenol, (R)-SO', serve as convenient chiral auxiliaries for the conversion of racemic starting complexes (1 a: pp=2,2'-bipyridine; 1 b: pp=5,5'-dimethyl-2,2'-bipyridine; 1 c: pp=1,10-phenanthroline) into single diastereomers Λ-[Ru(pp)(2) {(R)-SO}]PF(6) (Λ-(S)-2 a-c) or Λ-[Ru(pp)(2) {(R)-SO'}]PF(6) (Λ-(S)-2 a') under a thermodynamically controlled dynamic transformation. The complexes Λ-(S)-2 a-c and Λ-(S)-2 a' themselves are direct precursors for the generation of optically active ruthenium-polypyridyl complexes by trifluoroacetic-acid-induced replacement of the sulfinylphenolate auxiliaries with bidentate pp ligands under retention of configuration, thereby affording Λ-[Ru(pp)(3) ](PF(6) )(2) (3 a-c) complexes with high enantiomeric ratios of ≥98:2. In particular, by employing the methoxy-modified chiral auxiliary (R)-SO', enantiomeric ratios of >99:1 were reached. In the strategy introduced here, the high steric crowding of an octahedral coordination sphere was exploited by placing a sulfur-based stereocenter in direct proximity to the ruthenium stereocenter, thereby leading to a large difference in the stabilities of the intermediate Λ-S and Δ-S diastereomers and thus providing the opportunity to find suitable reaction conditions for conversion of the destabilized diastereomer into the thermodynamically more-stable one. This method should be of high practical value for the asymmetric synthesis of ruthenium-polypyridyl complexes because it allows one to use readily available racemic ruthenium complexes as starting materials.
Authors:
Zhijie Lin; Lei Gong; Mehmet Ali Celik; Klaus Harms; Gernot Frenking; Eric Meggers
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Publication Detail:
Type:  Journal Article     Date:  2010-12-10
Journal Detail:
Title:  Chemistry, an Asian journal     Volume:  6     ISSN:  1861-471X     ISO Abbreviation:  Chem Asian J     Publication Date:  2011 Feb 
Date Detail:
Created Date:  2011-01-21     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101294643     Medline TA:  Chem Asian J     Country:  Germany    
Other Details:
Languages:  eng     Pagination:  474-81     Citation Subset:  IM    
Copyright Information:
Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Affiliation:
Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Strasse, 35043 Marburg (Germany), Fax: (+49) 6421-2822189.
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