Synthesis, structure, and anion binding of functional oxacalixarenes
Oxacalixarenes obtained from the highly efficient, one-pot SNAr reaction were post-macrocyclization functionalized through the reduction of nitro groups and hydrolysis of the ester groups to obtain several derivatives of desired solubility. The difficulties in basic hydrolysis of ester groups were overcome via developing an acid hydrolysis method for tert-butyl ester derivatives of this class. The synthesis of symmetrical oxacalixarenes from an unsymmetrically substituted precursor was also explored via a multiple step fragment coupling approach. Compounds 17 & 18 adopted 1,3-alternate conformations in the solid state as most oxacalixarenes did, and a chair (zigzag) conformation was revealed for tetraamido oxacalixarene (6a) by X-ray single crystal analysis. The tetraureido oxacalixarene (7) showed strong association towards various anions such as F−, Cl−, Br−, I−, Ac−, and HSO4− with a 1 : 1 stoichiometry as revealed by 1H NMR analysis and UV-vis measurements.
- This article is part of the themed collection: Supramolecular chemistry in OBC