Dynamic covalent binding and chirality sensing of mono secondary amines with a metal-templated assembly

The recognition and analysis of mono-functionalized organics is an intensive area of research in organic chemistry. Toward this end, an in situ-generated metal-templated dynamic multi-component covalent assembly for the reversible binding and chirality sensing of mono secondary amines is presented. The reaction of pyridine-2-carboxyaldhyde, di(2-picolyl)amine, zinc triflate, tetrabutylammonium chloride, and a series of secondary amines, affords tripodal aminal zinc complexes. The dynamic nature of the system was demonstrated by component exchange of both amines and aldehydes. The equilibrium can be modulated by changing counteranions, concentrations, as well as structural feature of the amines. The competition between two iminium pathways resulted in a unique distribution of components. Due to the enantiotopicity of iminiums, decent diastereoselectivity was observed for chiral secondary amines. The resulting diastereomeric helical complexes were employed for the determination of enantiomeric excess with high accuracy. (C) 2015 Elsevier Ltd. All rights reserved.