Synthesis and Conformational Property of Tannin-like p-tert-Butylcalix[4]arene 1,3-Diesters Stabilized by Intramolecular Hydrogen Bonds

Abstract

Tannin-like p-tert-butylcalix[4]arene 1,3-digallate was synthesized, and its conformational property was investigated by dynamic (1)H NMR and X-ray crystallography. It was found that the 3-OH (or 5-OH) group of the galloyl group in p-tert-butylcalix[4]arene 1,3-digallate is placed at the position where an unusual nonbonded close contact is observed between the OH group and the aromatic ring of the galloyl group facing each other. The calixarene 1,3-diesters of various hydroxybenzoic acids were also prepared, and the conformational properties of those calixarenes were compared with that of p-tert-butylcalix[4]arene 1,3-digallate. A significant contribution of the 3- and 5-OH groups in pendant groups toward the close contact was found. It was suggested that the conformation of p-tert-butylcalix[4]arene 1,3-digallate was stabilized by intramolecular hydrogen bonds including OH.O and OH-pi interactions.

Two different conformations of 25,27-bis(3-pyridylcarboxylate)- 26,28-dihydroxy-calix[4]arene in solid state

“…Compound 1 was prepared by reaction of terthydroxycalix [4]arene and nicotinyl chloride hydrochloride in 30 % yield. The single crystals of compound 1 were obtained by diffusing methanol to dichloromethane solution of 1 at room temperature.…”

“…After a few days, two types of single crystals, namely colorless and light yellow, were formed, which were suitable for single-crystal X-ray diffraction analysis. Figure 1 shows two different conformations of calix [4]arene derivative 1 in the solid state. In one of these the molecules in the colorless crystal adopt a partial cone conformation (A), in which one of the unsubstituted rings is oriented in an opposite direction.…”

“…The calix [4]arenes and analogues interconvert between four discrete conformations (cone, partial cone, 1,2-alternate, and 1,3-alternate) in solution. 1 Although there have been many recent studies of crystal structures and the conformational behavior of calixarenes, 2-10 separate conformers have rarely been isolated as solids.…”

“…1 Although there have been many recent studies of crystal structures and the conformational behavior of calixarenes, 2-10 separate conformers have rarely been isolated as solids. 11 Such as, Atwood et al 12 found that the conformation of 25,26,27,28-tetramethoxy-p-tert-butylcalix [4]arene is modified either to 1,2-alternate or to 1,3-alternate through complexation with different aluminum alkyl compounds. Marquez and Sessler et al 13 revealed the presence of four different macrocyclic conformations in the solid state by using different substrates.…”

“…Marquez and Sessler et al 13 revealed the presence of four different macrocyclic conformations in the solid state by using different substrates. Recently, we reported that an interlocked 2-D supramolecular architecture was constructed through the synergistic intermolecular interactions of 25,27-bis(4-nitrobenzoate)-26,28-dihydroxy-calix [4]arene in the crystal, which were highly stabilized by the regular π-π and offset stacking, edge-to-face, and/or dipole-dipole interactions. 9 In order to improve our understanding of the relationship between the structure and the functional groups, we have carried out to synthesis of novel calix [4] …”