Alajos Grün

Studies on calix(aza)crowns, I. Synthesis, alkylation reactions and comprehensive NMR investigation of capped calix[4]arenes

Abstract Calix[4]arenes capped by diamide bridges in 1,3-position on the lower rim were synthesized. Regioselective alkylations of compounds 2 afforded 3, 4 O- and N-alkylated derivatives. Comprehensive NMR investigations were made to reveal the conformation of calix(aza)crowns 2, 3, 4.

Chromogenic calix[4]arene as ionophore for potentiometric and optical sensors

Chromogenic calix[4]arene derivative was synthesized and tested as an ionophore for potentiometric and optical sensors. Distinct sodium selectivity was observed with this ionophore based, plasticized PVC membranes in potentiometric measurements suggesting their utility for biological applications. Optode membranes exhibited sodium sensitivity in the 5 x 10(-2) -10(-4)M concentration range. The optical sensitivity was improved by the use of an internal, lipophilic base (TDDA). The operation of the optical sensor is in accordance with the ion-exchange theory.

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.

Studies on calix(aza)crowns, II. Synthesis of novel proximal doubly bridged calix[4]arenes by intramolecular ring closure of syn 1,3-and 1,2-ω-chloroalkylamides☆

Inherently chiral calix[4]arenes (9,10) with carboxamide bridges spanning the proximal positions on the lower rim and 18 achiral counterparts have been synthesized by double intramolecular cyclization of 7b,8b 1,3-and 17 1,2-bis-chloroalkylamides. The conformational analysis of the 1.3- and 1,2-disubstituted calixarene intermediates 5–8 and 15–17 proved an equilibrium of two distorted cone conformations. The success of ring closure was strictly dependent on the chain length of the open chain precursors.

Synthesis of chiral 1,3-calix[4](crown-6) ethers as potential mediators for asymmetric recognition processes

Abstract Novel chromogenic 1,3-calix[4](crown-6) derivatives comprised of 1,1′-binaphthyl-, methyl-α- d -glucoside-and d -mannitol moieties in the crown ether ring have been synthesized. UV–vis spectroscopic measurements of the 2,4-dinitrophenylazo chromogenic molecules indicated noticeable chiral discrimination associated with coloration towards primary amine enantiomers.

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.

An easy access to tetra-o-alkylated calix[4]arenes of cone conformation

Abstract Fully O-alkylated calix[4]arenes have been synthesized by the alkylation of p-tertbutylcalix[4]arene and its 1,3-dialkylated derivatives in liquid-liquid phase-transfer catalytic process. 1H 4 and 1H 2 R 2 could effeciently be deprotonated by aqueous NaOH (50% w/w)-toluene system and alkylated with alkyl (aralkyl, allyl) halogens in good yields affording calix[4]arene tetraethers of cone conformation.

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.

Photochromism of a spiropyran derivative of 1,3-calix[4]crown-5

A new spiropyran derivative containing a calixcrown ring has been synthesised. Thermal conversion from merocyanine to the spiropyran form was studied in ethanol and in acetonitrile, and equilibrium and kinetic data were compared with those of the parent 6-nitrospiropyran. The kinetics of thermal decay of the merocyanine form of the calixcrown-spiropyran molecule shows a biexponential character in both solvents, while the decay is much slower in ethanol than in acetonitrile.

Microwave-Assisted Organophosphorus Synthesis

The spread of microwave (MW) equipment has brought about a tremendous development in synthetic organic chemistry. This environmentally friendly methodology, associated often with solventless conditions, has also had a positive impact on organophosphorus chemistry, allowing new reactions to be carried out, or increasing the rate, selectivity and yield. In special cases, MW irradiation may replace phase transfer or other kinds of catalysts. Reactions, such as the derivatization of phosphinic acids, the inverse Wittig protocol, Diels– Alder cycloadditions, fragmentation-related phosphorylations, phospha-Michael additions, Kabachnik–Fields condensations, the addition of >P(O)H species to carbonyl compounds, substitution of