A New Approach to the Synthesis of Phenol-Containing Macroheterocycles

Abstract

A one-step method for the synthesis of new phenol-containing cryptands and cryptohemispherands by treating N,"-bis(methoxymethy1)diazacrowns with the appropriate bis-and trisphenols is reported. This method, based on a special Mannich reaction, gives cyclized products without the need for protecting groups and high dilution conditions. Unusually high yields of cryptohemisherands were realized using a relatively high concentration of the starting materials (50 mmol/ L) and in the absence of metal cations as template agents in the reaction mixture. These excellent yields can be explained by intramolecular hydrogen bonding which prevents polycondensation. This new method also allowed preparation of new phenol-containing cylindrical tricyclic ligands by first forming bisphenol-substituted diaza-18-crown-6 at 80 "C followed by its reaction with a second bis(methoxymethy1)-substituted diaza-18-crown-6 at 144 "C. Crystal structures of two cryptohemispherands are reported herein. A shorter internal distance between N and 0 atoms in 27 as compared to 6 (R = NOz, n = m = 2) indicates intramolecular hydrogen bonding in phenol-containing macrocycle 27.

Diaza-18-Crown-6 Ligands Containing Two Aminophenol Side Arms: New Heterobinuclear Metal Ion Receptors

“…Methoxymethylamines, prepared quantitatively by treating the azacrown ethers with paraformaldehyde in MeOH, have been used successfully in functionalizing azacrown ethers. , This variation prevents the interaction of free formaldehyde with substances undergoing aminomethylation and possible side reactions between amine groups of the azacrown and functional groups such as carbonyls on the receptor molecules. Preformation of the methoxymethylamines also allows the reaction to be performed in nonpolar solvents (CCl 4 , C 6 H 6 , toluene, or xylene), which is important for some self-assembly cyclization processes . A variety of phenol-, β-naphthol-, and amide-, sulfonamide-, imide- or azole-substituted monoaza-, diaza-, and pyridinoaza-crown ethers and cryptands have been prepared by this method. ,− One-pot Mannich reactions 6 of 4,13-diaza-18-crown-6 with paraformaldehyde and a series of para -substituted phenols in refluxing benzene have been shown to give double-armed proton-ionizable crown ethers in good yields .…”

Proton-diionizable Bis-calix[4]azacrown Ether through Mannich Reaction

“…We obtained 2 and 3 with 8% and 55%, respectively. The presence of only one singlet for methylene bridge of the calixarene unit in the 1 H NMR (about 3.80 ppm) and 13 C NMR (about 38 ppm) spectra clearly established that both 2 and 3 are in the 1,3-alternate conformation. 7 Consistent with the NMR results is the X-ray crystal structure of 3 as shown in Figure 1.…”

“…Under neutral condition, no significant extractability and selectivity were observed. 13 In contrast, basic extraction (pH 12) gave remarkable extractability and selectivity for Mg 2+ ion when 5.0 mM of metal ion and 2.5 mM of 3 were used (Figure 2). More than 100 % extractability for Mg 2+ ion indicates that compound 3 forms 1 : 2 (ligand : metal ion) complex.…”

Intrinsic Fluorescence of 1,3-Benzoxazinephanes

“…1 Due to the aromatic rings' high electron density, these macrocycles have interesting properties and great potential as hosts due to their ability to trap guest molecules, mainly through non-covalent interactions such as Van der Waals, -cation, ion-dipole, dipole-dipole interactions and hydrogen bonds. 2,3 In addition to their interesting electron characteristics and molecular topology, the size of the cavity and solubility can be modulated by varying the spacer length and the functionalization of the outside of the cavity on either the aromatic rings or the spacers. 4,5 The azacyclophanes (cyclophanes having one or more nitrogen atoms in their structure) represent an interesting group of synthetic receptors combining electron-donor and acid-based properties of nitrogenated heterocycles with the -interaction capacity of cyclophanes.…”