Viktor Csokai

Synthesis and alkali cation extraction ability of 1,3-alt-thiacalix[4]mono(crown) ethers

Abstract The first representatives of 1,3-alt-thiacalix[4]mono(crown-5 and -6) ethers were synthesized by the cyclocondensation of 25,27-dialkoxythiacalix[4]arenes with tetraethylene glycol ditosylate and 1,14-diiodo-3,6,9,12-tetraoxatetradecane, respectively. The complexing abilities of ligands were determined by the alkali (Li+, Na+, K+, Rb+, Cs+) picrate extraction method.

An expedient route to p-tert-butylthiacalix[4]arene 1,3-diethers via Mitsunobu reactions

Regioselective distal dialkylation of p-tert-butylthiacalix[4]arene with alcohols was performed under the Mitsunobu protocol using the DEAD/TPP system. The method provides a versatile tool for obtaining 1,3-diethers with different functional groups in the alkyl chains.

Unprecedented cyclisations of calix[4]arenes with glycols under the Mitsunobu protocol. Part 1: A new perspective for the synthesis of calixcrowns

Selective ring closures of p-tert-butylthiacalix[4]arene and p-tert-butylcalix[4]arene with oligoethylene glycols were performed under the Mitsunobu protocol using the DEAD/TPP system. The method opens a new perspective for the syntheses of 1,3-calixcrowns.

Synthesis and Structure Elucidation of Chromogenic Calix[4]arene Indophenols Capped by Carboxamide Bridges

Calix[4]arenes capped by di- and triamide bridges on the lower rim were used to synthesize 2,3,4,5 chromogenic molecules supplied with indophenol indicator unit(s). The endo/exo quinoid tautomerism of the chromophore and the mechanism of the coloration process were studied by NMR spectroscopy.

Synthesis and Conformational Analysis of Dicationic N,N′‐Bridged Bis(benzimidazolium) and Bis(imidazolium) Macrocycles

Two-step alkylations of benzimidazole, 2-methylbenzimidazole, and imidazole at their nitrogen atoms with various bifunctional alkylating agents have afforded a series of 16-membered quaternary azacyclophanes. Of these macrocycles, those bearing methyl or methoxy groups on the azole or at the aromatic bridges have been found to exist as mixtures of conformers. In some cases, the structures of the conformers have been determined by NMR methods and X-ray crystallography, and have been correlated with the results of a computer-aided conformational search.

Unprecedented Cyclizations of Calix[4]arenes with Glycols under the Mitsunobu Protocol. Part 4. An Expedient Route to Thiacalix[4](Aza and Thia)Crowns

The Mitsunobu cyclization of p-t-butylthiacalix[4]arene with glycols was expanded to oligoethylene glycol analogues composed of O, S and N atoms in the chain. In this way a number of 1,3-thiacalix[4]monocrowns have been synthesized, offering simple and general access to a large variety of crowned thiacalixarenes. The binding properties of some ligands towards transition metal cations have been studied by 1H NMR, UV/Vis spectroscopic and potentiometric methods.

The First Synthesis of Functionalized Oxacalix[4]crown Ethers

O-alkylation and cyclization of 25,27-dihydroxy-4,6,16,18-tetranitro-oxacalix[4]arene were performed with mono- and bifunctional alkylating agents under basic conditions. In this way several 1,3-alt oxacalix[4]crown-4, 5 and 6 ethers were synthesized and characterized