C. David Gutsche

Calixarenes 9 : Conformational isomers of the ethers and esters of calix[4]arenes

Abstract Calix[4]arene (1A), p-t-butylcalix[4]arene (1B), and p-allylcalix[4]arene (1C) have been converted to various derivatives, including the methyl, ethyl, allyl, benzyl and trimethylsilyl ethers and the acetates. Although the parent calixarenes exist preferentially in the cone conformation, they are conformationally flexible and at room temperature interconvert at a rate of ca 100 sec−1. All but the methyl ethers, on the other hand, are conformationally rigid at room temperature. The preferred conformations in most cases are the cone and partial cone, depending on the derivative formed (i.e. methyl and ethyl ethers favor the partial cone; benzyl and trimethylsilyl ethers favor the cone). In the cases of the allyl ethers and the acetates the p-substituents appear to influence the conformational outcome (i.e. 1A and 1B form the allyl ethers in the partial cone and cone conformation, respectively; 1A and 1B form the acetates in the 1,3-alternate and partial cone conformation, respectively). The conformationally rigid calixarene derivatives in the cone and partial cone conformations belong to the small group of synthetic compounds that contain a permanent cavity (a “changeless calix”) whose dimensions are large enough to encapsulate other molecules.

Calixarenes. 22. Synthesis, properties, and metal complexation of aminocalixarenes

Preparation de calix [4] arene et de derives fonctionnalises. Formation de complexes avec Ni, Cu, Pd, Co et Fe divalents. Donnees RMN et IR

Calixarenes. 23. the complexation and catalytic properties of water soluble calixarenes

Abstract A series of-water-soluble calixarenes containing dialkylamino groups and carboxyl groups have been prepared by the p-quinonemethide route of functionalization. The formation of host-guest complexes between these calixarenes and nine aromatic hydrocarbons ranging in size from durene to decacyclene has been investigated, and a correlation between the dimensions of the hydrocarbons and the “lower rim” of the calixarene, containing the array of OH groups, has been made. A study of the effect on the acid-catalyzed hydration of N-benzyl-1,4-dihydronicotinamide by p-(carboxy-ethyl) calix[n]arenes (n = 4,5,6,7,8) has shown that the calix[6]arene is more effective than either its larger or smaller analogs.

Calixarenes 21: The conformations and structures of the products of aroylation of the, calix[4]arenes

Abstract The aroylatlon of eallx[4]arene (1), p-tert -butylealix[4]arene (2) and p -allylcalix[4]arene (3) with benzoyl chloride and a variety of p -substituted benzoyl chlorides has been carried out via AlCl3-catalyzed reaction and NaH-induced reaction. The products are tetra-aroylates that exist in the cone, partial cone, and/or 1,3-alternate conformation. It is shown that the distribution anong these conformers is dependent on a variety of factors including temperature, aroylating agent, calixarene, and solvent. When 1 is eaterified by the AlCl3 procedure lower temperature tends to slightly favor the partial cone conformation, while higher temperature favors the 1,3-alternate conformation. When 3 is esteritied by the NaH method aroyl chlorides carrying electron-releasing p -substituents favor the 1,3-alternate conformers; those carrying electron-withdrawing substituents favor the cone conformers, the distribution between the conformers correlating quite well with the Hammett σ constants for the p -substituents of the aroylating agents. When 2 is esterified by the NaH method it shows a greater tendency to produce the cone conformer than does 3, the former undergoing slower conformational inversion than the latter. On the basis of these observations it is postulated that the conformer distribution is dependent on the relative rates of the conformational inversion process and the aroylation process, viz. faster aroylation leading to cone conformers or partial cone conformers and slower aroylation leading to 1,3-alternate conformers.

Calixarenes. 5. Dynamic NMR characteristics of p-tert-butylcalix[4]-arene and p-tert-butylcalix[8]arene

Abstract The near identity of the temperature dependent 1H-NMR spectra of p-tert-butylcalix-[4]- and calix[8]arene in CDCl3 and bromobenzene-d5 is shown to be drastically altered in pyridine-d5, attributable to disruption of intramolecular hydrogen bonding.

Calixarenes 11. Crystal and molecular structure ofp-tert-butylcalix[8]arene

Monoclinic prisms were obtained by slow evaporation of a pyridine solution ofp-tert-butylcalix[8]arene: space groupP21/c,a=20.312(3),b=23.020(2),c=20.006(6) Å; β=113.05(2)0;V=8707.6 Å3;Z=4. Refinement led to anR value of 0.166 for 4231 reflections which, although high, is sufficient to establish the conformation of the molecule as a pleated loop in which the eight hydroxyl groups are arranged in a slightly undulating, almost planar, intramolecularly hydrogen bonded cyclic array. The possible inferences for the conformation ofp-tert-butylcalix[8]arene in solution are discussed.

Synthesis and crystal structures of mono-potassium salts of calix[4]arene and p-tert-butylcalix[4]arene

Abstract The mono-potassium salts obtained by the action of K2CO3 on calix[4]arene and p-tert-butylcalix[4]arene are found to possess very similar solid-state dimer structures that differ only in the presence of a cation–π interaction in the former. The mono-potassium salt obtained by the action of KOSiMe3 on p-tert-butylcalix[4]arene, on the other hand, is found to possess a monomeric structure.

Topics in Calixarene Chemistry

Several facets of calixarene chemistry have been investigated including the mechanism of their formation by the base-induced condensation of phenols and formaldehyde, procedures for introducing functional groups onto the ‘upper rim’ and ‘lower rim’ of calixarenes, the conformational behavior of calixarene oxyanions, the formation of complexes in aqueous and nonaqueous systems, and the application of calixarenes as catalysts.

Calixarenes. II. The isolation and characterization of the calix[4]arene and the bishomooxacalix[4]arene from A p-t-butylphenol-formaldehyde condensation product

Abstract The base-catalyzed condensation of p-t butylphenol and formaldehyde, which yields a cyclic octamer (I, n=8) as the major product, has been shown to also yield a cyclic tetramer (I, n=4) and a bischomooxa cyclic tetramer (II).

The mechanism of the acid-catalyzed decomposition of the farnesyl phosphates

Abstract The rates and (in some cases) products of the acid-catalyzed decomposition of (Z,E)- and (E,E)-farnesyl phosphate, (Z,E)- and (E,E) - 1,1 - dideutereofarnesyl phosphate, (Z)- and (E) - 6,7,10,11 - tetrahydrofarnesyl phosphate, and t-butyl phosphate have been studied in an attempt to determine whether (Z,E)-farnesyl phosphate ionizes with intramolecular assistance from the C-6/C-7 double bond or via an unassisted process leading to a simple allylic cation. Data in support of both possibilities are adduced, but it is concluded, primarily on the basis of the secondary deuterium kinetic isotope effects, that the ionization involves little, if any, assistance from the double bond.