Selective O-Alkylation of the Crown Conformer of Tetra(4-hydroxyphenyl)calix[4]resorcinarene to the Corresponding Tetraalkyl Ether

Abstract

Reactions of glycidyl methacrylate with the crown and chair conformers of tetra(4-hydroxyphenyl)calix[4]resorcinarene were studied. The reactions were done over epoxide groups present in the ester, which can easily undergo an opening reaction with hydroxyl groups in the macrocyclic system. Initially, epoxidation reactions were carried out with pure conformers, and it was observed that the reaction between tetra(4-hydroxyphenyl)calix[4]resorcinarene fixed in the chair conformation does not occur, while for the molecule fixed in the crown conformation only one tetraalkylated derivative was obtained. The obtained product was characterized using IR, 1H-NMR, 13C-NMR, COSY, HMQC and HMBC techniques. An exhaustive NMR study showed that the reaction is selective at the hydroxyl groups in the lower rim, without affecting the hydroxyl groups in the upper rim. In addition, the RP–HPLC analysis of the epoxidation reaction mixture, using both crown and chair conformers, showed that only the crown conformer reacted under tested conditions. Finally, a comparative study of the reactivity of tetranonylcalix[4]resorcinarene with glycidyl methacrylate showed that the reaction does not take place. Instead, the formation of the tetranonylcalix[4]resorcinarene tetrasodium salt was observed, which confirms that the hydroxyl groups in the upper rim are unreactive under these conditions.

Surface Modification of Poly(GMA-co-EDMA-co-MMA) with Resorcarenes

“…According to this analysis, the crown conformer of 4 was the one fixed on the copolymer surface, maintaining the selective character of the process previously observed in solution. 25 In order to determine if the medium influenced the modification of the polymer, the reaction was performed with resorcarene 4 in acidic and basic medium. In both reactions the oxirane rupture is generated by producing diol (2,3-dihydroxypropyl methacrylate) or its isomer (1,3-dihydroxypropyl methacrylate), the latter being a minor product.…”

“…It was found that the glycidylmethacrylate oxirane opening reaction by using tetra(p-hydroxyphenyl)resorcarene proceeds selectively at the lower rim hydroxyl group without a reaction of the upper rim hydroxyl groups, observing that this trend in solid phase is similar to that observed in solution. 25…”

Calixarenes: Generalities and Their Role in Improving the Solubility, Biocompatibility, Stability, Bioavailability, Detection, and Transport of Biomolecules

“…Polyhydroxylated platforms such as calixarenes, resorcinarenes, or pyrogalloarenes (Figure 1) are a very interesting class of compounds. They have a remarkable ability to act as receptors for a variety of guest species, depending on their structural properties [23,24,25,26,27], which can be modified by changing the size of the substituents or by adding functional groups as a part of the scaffold [28,29,30,31,32]. Among the described macrocyclic compounds, calixarenes are probably the most promising for application in the area of host–guest recognition of toxicological molecules.…”

Experimental Comparative Study of Dynamic Behavior in Solution Phase of C-Tetra(phenyl)resorcin[4]arene and C-Tetra(phenyl)pyrogallol[4]arene

“…Continuing with our studies of the structure of polyhydroxylated platforms [12,33,40,41], we found that the bulky aromatic substituents on the lower rim of polyhydroxylated platforms in cone conformation exhibited a dynamic behavior, which stimulated interest in examining the conformational preferences. For this purpose, in this article, the comparative behavior of Ctetra(phenyl)-resorcin [4]arene (1) and C-tetra(phenyl)pyrogallol [4]arene (2) compounds is studied using 1 H-NMR and 13 C-NMR data and dynamic 1 H-NMR spectra.…”