Dynamic multi-component covalent assembly for the reversible binding of secondary alcohols and chira

Abstract

Reversible covalent bonding is often used for the creation of novel supramolecular structures, multi-component assemblies and sensing ensembles. Despite the remarkable success of dynamic covalent systems, the reversible binding of a mono-alcohol with high strength is challenging. Here, we show that a strategy of carbonyl activation and hemiaminal ether stabilization can be embodied in a four-component reversible assembly that creates a tetradentate ligand and incorporates secondary alcohols with exceptionally high affinity. Evidence is presented that the intermediate leading to binding and exchange of alcohols is an iminium ion. To demonstrate the use of this assembly process we also explored chirality sensing and enantiomeric excess determinations. An induced twist in the ligand by a chiral mono-ol results in large Cotton effects in the circular dichroism spectra indicative of the handedness of the alcohol. The strategy revealed in this study should prove broadly applicable for the incorporation of alcohols into supramolecular architecture construction. The reversible covalent binding of mono-alcohols with high affinity is challenging because of their poor nucleophilicity. A multi-component assembly has now been used to achieve reversible binding of secondary alcohols through iminium activation and product stabilization. Moreover, such assemblies can be used to determine alcohol chirality and enantiomeric excess.

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You, L., Berman, J. & Anslyn, E. Dynamic multi-component covalent assembly for the reversible binding of secondary alcohols and chirality sensing. Nature Chem 3, 943–948 (2011). https://doi.org/10.1038/nchem.1198

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