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Self-assembling Morphologies Obtained from Helical Polycarbodiimide Copolymers and Their Triazole Derivatives
Published on: February 7, 2017
Solvent-dependent self-discrimination of bis(2-hydroxyphenyl)diamides
Akinobu Matsuzawa1, Akihiro Nojiri, Naoya Kumagai
1Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Chemistry (Weinheim an Der Bergstrasse, Germany)
|April 9, 2010
Summary
Chiral diamides self-assemble into insoluble aggregates in specific solvents. This solvent-dependent self-discrimination enables high stereoselectivity in asymmetric catalysis, demonstrating a novel approach to chiral molecule synthesis.
Area of Science:
- Supramolecular Chemistry
- Organic Chemistry
- Crystallography
Background:
- Diamides with multiple hydrogen-bonding modules, such as valine-derived bis(2-hydroxyphenyl)diamide (1a), can exhibit complex self-assembly behavior.
- Solvent choice significantly influences the solubility and aggregation state of chiral organic molecules.
Purpose of the Study:
- To investigate the solvent-dependent self-discrimination of chiral diamides.
- To explore the potential of this phenomenon in achieving stereoselective synthesis.
Main Methods:
- Preparation and dissolution of enantiomers (R)-1a and (S)-1a in various solvents (dichloromethane, ethyl acetate, chloroform).
- Observation of aggregate formation and solubility differences.
- Analysis of crystal structures of racemic 1a obtained from different solvents.
- Testing the application of self-discrimination in a catalytic asymmetric reaction.
Main Results:
- Mixing (R)-1a and (S)-1a in dichloromethane rapidly formed an insoluble 1:1 heterochiral aggregate.
- Heterochiral 1a exhibited significantly lower solubility in halogenated solvents compared to ethyl acetate.
- Racemic crystal structures revealed distinct packing patterns correlating with solubility differences.
- The bis(2-hydroxyphenyl)diamide framework's hydrogen-bonding network drives specific self-aggregation.
- Low solubility of heterochiral 1a in halogenated solvents facilitated high stereoselectivity in asymmetric catalysis using low enantiomeric excess starting material.
Conclusions:
- Chiral diamides demonstrate pronounced solvent-dependent self-discrimination, leading to the formation of insoluble heterochiral aggregates.
- Differences in crystal packing patterns underpin the observed solubility variations in different solvents.
- This specific self-aggregation behavior can be effectively utilized to achieve high stereoselectivity in catalytic asymmetric reactions.
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