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Developing a New Class of Axial Chiral Phosphorus Ligands: Preparation and Characterization of Enantiopure Atropisomeric Phosphinines
Author(s) -
Müller Christian,
Pidko Evgeny A.,
Staring Antonius J. P. M.,
Lutz Martin,
Spek Anthony L.,
van Santen Rutger A.,
Vogt Dieter
Publication year - 2008
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.200800175
Subject(s) - racemization , enantiopure drug , enantiomer , atropisomer , circular dichroism , chiral column chromatography , chemistry , homogeneous , absolute configuration , stereochemistry , catalysis , crystallography , organic chemistry , physics , thermodynamics , enantioselective synthesis
Both enantiomers of the first atropisomeric phosphinine ( 1 ) have been isolated by using analytical HPLC on a chiral stationary phase. The enrichment of one enantiomer and a subsequent investigation into its racemization kinetics revealed a barrier for internal rotation of Δ ${G{{{\ne}\hfill \atop 298\hfill}}}$ =(109.5±0.5) kJ mol −1 , which is in excellent agreement with the theoretically predicted value of Δ ${G{{{\ne}\hfill \atop 298\hfill}}}$ =116 kJ mol −1 . Further analysis with UV and circular dichroism spectroscopies and density functional theory calculations led to the determination and assignment of the absolute configurations of both enantiomers. These results are the basis for future investigations into this new class of axially chiral phosphinine‐based ligands and their possible applications in asymmetric homogeneous catalysis.