Absolute Asymmetric Synthesis: Viedma Ripening of [Co(bpy) sub(3)] super(2+) and Solvent-Free Oxidation to [Co(bpy) sub(3)] super(3+)

Syntheses of [Co(bpy) sub(3)] super(2+) yield racemic solutions because the Delta - and Lambda -enantiomers are stereochemically labile. However, crystallization and attrition-enhanced deracemization can give homochiral crystal batches of either handedness in quantitative yield. Subsequently, solven...

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Bibliographic Details
Published in:Chemistry : a European journal 2015-07, Vol.21 (30), p.10630-10633
Main Authors: Bjoremark, Per Martin, Jonsson, Johan, Hakansson, Mikael
Format: Article
Language:English
Subjects:
Asymmetry
Bromine
Crystals
Inert
Oxidation
Ripening
Synthesis
Vapour
Online Access:Get full text
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Summary:Syntheses of [Co(bpy) sub(3)] super(2+) yield racemic solutions because the Delta - and Lambda -enantiomers are stereochemically labile. However, crystallization and attrition-enhanced deracemization can give homochiral crystal batches of either handedness in quantitative yield. Subsequently, solvent-free oxidation with bromine vapour fixes the chirality because [Co(bipy) sub(3)] super(3+) does not enantiomerize in solution at ambient temperature. This combination of Viedma ripening and the labile/inert Co super(II)/Co super(III) couple constitutes a convenient method of absolute asymmetric synthesis. Large quantities of enantiopure [Co(bpy) sub(3)] super(3+) can be accessed by attrition-enhanced deracemization followed by solvent-free oxidation with bromine vapor. Subsequently, solvent-free oxidation with bromine vapor gives a quantitative yield of enantiopure [Co(bpy) sub(3)] super(3+), which does not racemize in solution (see scheme).
ISSN:0947-6539
1521-3765
DOI:10.1002/chem.201500876