title: Annelated Calixarenes Composed of Calix[4]arenes with Hydroxy Groups in the Endo and Exo Position.
abstract: Various phenol-derived calix[4]arenes (3) bearing four hydroxy groups in the exo position have been prepared by uncatalyzed condensation of suitable dimers or tetramers with formaldehyde in xylene in yields up to 44%. The tetra-tert-butyl compound (3a) has been shown by X-ray analysis to adopt a regular cone conformation (nearly identical in shape with the endo isomer) with two intramolecular O-H.O hydrogen bonds, while the corresponding dimer (6c) prefers a conformation (not possible in the calixarene) with two intramolecular O-H.pi(arene) interactions. Condensation of exo-calix[4]arenes 3f,g with free ortho positions (easily available by debutylation) with bisbromomethylated dimers gave annelated double (9) and triple (10) calixarenes consisting of endo- and exo-calix[4]arene substructures in yields up to 24% and 10%, respectively. Molecular dynamics calculations suggest that the exo-calixarene part in 9 is less mobile than the entirely flexible 3, while the endo-calixarene part shows a higher mobility than usual. A complete interconversion cone --> cone is impossible, however, which enables the construction of inherently chiral molecules.
authors.affiliation: Institut für Organische Chemie, Johannes Gutenberg Universität, J.-J.-Becherweg 34 SB1, D-55099 Mainz, Germany, Fachbereich Chemie, Universität Potsdam, Am neuen Palais 10, D-14415 Potsdam, Germany, Department of Chemistry and Biochemistry, University of Guelph, Guelph, Ontario, Canada N1G 2W1, and Institut für Biochemie, Fachbereich Biochemie/Biotechnologie, Martin-Luther-Universität Halle-Wittenberg, Weinbergweg 16a, D-06099 Halle, Germany.
authors.forename: Volker
authors.initials: V
authors.lastname: Böhmer
authors.forename: Ralph
authors.initials: R
authors.lastname: Dörrenbächer
authors.forename: Michael
authors.initials: M
authors.lastname: Frings
authors.forename: Mathias
authors.initials: M
authors.lastname: Heydenreich
authors.forename: Diana
authors.initials: D
authors.lastname: de Paoli
authors.forename: Walter
authors.initials: W
authors.lastname: Vogt
authors.forename: George
authors.initials: G
authors.lastname: Ferguson
authors.forename: Iris
authors.initials: I
authors.lastname: Thondorf