title: Synthesis, Optical Resolution and Complexation Properties of Inherently Chiral Monoalkylated p-tert-Butyl-(1,2)-calix[4]crown Ethers.
abstract: Reaction of mono-O-alkylated calix[4]arenes 2 with tri- to pentaethylene glycol ditosylates and K(2)CO(3) affords asymmetrical (1,2)-calix[4]crown ether derivatives 3 as the main product, along with minor amounts of calix[4]arene dimers 4 and mixed syn-distal di-O-alkylated calix[4]arenes 5. A reaction mechanism for the formation of 3-5 is proposed, and the NMR spectral features of these products are briefly discussed. Evidence of the chirality of 3 was provided by diastereomeric interaction with enantiopure alkylammonium salts. The enantiomeric resolution of racemates 3 was achieved by direct HPLC separation, using chiral stationary phases. A screening of the complexing abilities of pyridino-(1,2)-calix[4]crown ethers 3a-c by extraction studies from water into CH(2)Cl(2) showed a low extraction level of alkali, alkaline earth, and heavy metal picrates, while up to 25% extraction was found for Ag(+). UV and pH-metric measurements of 3a-c with silver picrate in THF indicate the formation of 1:1:1 (metal:ligand:picrate) species, with log K's in the range 3.1-3.7.
authors.affiliation: Laboratoire de Chimie-Physique de l'ECPM, URA 405 au CNRS, Université Louis Pasteur, 1, rue Blaise Pascal, 67000 Strasbourg, France, Dipartimento di Scienze Chimiche, Università di Catania, Viale A. Doria 6, I-95125 Catania, Italy, and Dipartimento di Chimica Organica e Biologica, Università di Messina, Salita Sperone 31, I-98166 Vill. S. Agata, Messina, Italy.
authors.forename: Francoise
authors.initials: F
authors.lastname: Arnaud-Neu
authors.forename: Salvatore
authors.initials: S
authors.lastname: Caccamese
authors.forename: Saowarux
authors.initials: S
authors.lastname: Fuangswasdi
authors.forename: Sebastiano
authors.initials: S
authors.lastname: Pappalardo
authors.forename: Melchiorre F.
authors.initials: MF
authors.lastname: Parisi
authors.forename: Ada
authors.initials: A
authors.lastname: Petringa
authors.forename: Grazia
authors.initials: G
authors.lastname: Principato