Correlating sterics parameters and diastereomeric ratio values for a multicomponent assembly to predict exciton-coupled circular dichroism intensity and thereby enantiomeric excess of chiral secondary alcohols


Linear free energy relationship (LFER) substituent parameters are commonly employed for exploring reaction mechanisms and very recently have been used to guide the design of asymmetric catalysts, but their usage in dynamic covalent chemistry is rare. Herein, the properties of an in situ-generated dynamic multicomponent covalent assembly that creates tris(pyridine) metal complexes incorporating chiral secondary alcohols were explored using LFER-based steric parameters. The diastereomeric ratio (dr) of the assembly was correlated with the magnitude of the exciton-coupled circular dichroism (ECCD) induced by chiral alcohols. Charton steric parameters were successfully correlated with the dr values. Through the combination of these correlations, both the dr and CD intensity were predicted for test alcohols. These correlations were also employed to measure a few new Charton parameters. Finally, the prediction of enantiomeric excess (ee) of test samples with various alcohol structures was also successfully achieved. The prediction of spectral properties in advance by using well-established steric parameters is shown to be useful for rapid ee screening because the need for calibration curves and enantiomerically enriched samples is avoided. © 2012 American Chemical Society.

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Journal of the American Chemical Society