Conformational Aspects of the O-acetylation of C-tetra(phenyl)calixpyrogallol[4]arene

Abstract

Reaction between pyrogallol and benzaldehyde results in a conformational mixture of C-tetra(phenyl)pyrogallol[4]arene (crown and chair). The conformer mixture was separated using crystallization procedures and the structures were determined using FTIR, 1H-NMR, and 13C-NMR. O-acetylation of C-tetra(phenyl)pyrogallol[4]arene (chair) with acetic anhydride, in pyridine results in the formation of dodecaacetyl-tetra(phenyl)pyrogallol[4]arene. The structure was determined using 1H-NMR and 13C-NMR finding that the product maintains the conformation of the starting conformer. On the other hand, the O-acetylation reaction of C-tetra(phenyl)pirogallol[4]arene (crown) under same conditions proceeded efficiently, and its structure was determined using 1H-NMR and 13C-NMR. Dynamic 1H-NMR of acetylated pyrogallolarene was studied by means of variable temperature in DMSO-d6 solution, and it revealed that two conformers are formed in the solution. Boat conformations for acetylated pyrogallolarene showed a slow interconversion at room temperature.

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.…”

“…On the other hand, those synthesized from aromatic aldehydes show a preference for producing chair-type isomers [10,11]. Even so, as with resorcinarenes, there are some cases where the tendency changes or an isomeric mixture is produced, depending on the synthesis conditions [12].…”

“…In the 1 H-NMR spectrum of 1a ( Figure S3), individual assignments of the protons were made based on their positions, multiplicities, integral values and comparison of spectral data with reported values of similar compounds [12,40]. In this way, the 1 H-NMR spectrum of 1a displayed the characteristic signal of a methine bridge at 5.63 ppm.…”

Recent advances in mass spectrometry studies of non-covalent complexes of macrocycles - A review

“…Calixarenes offer several possibilities for non-covalent interactions. The first possibility is due to their bowl-shaped which provides a π-electron rich cavity [74]. The binding interactions that take place in this cavity could be, π-system type with inorganic and organic cations or polar-π and CH-π with neutral molecules.…”