title: Calix[6]arene derivatives selectively functionalized at alternate sites on the smaller rim with 2-phenylpyridine and 2-fluorenylpyridine substituents to provide deep cavities.
abstract: The synthesis is described of calix[6]arene derivatives 4, 9, and 14 functionalized at alternate sites on the smaller rim with 4'-(pyrid-2' '-yl)phenylmethoxy, (6'-phenylpyrid-3'-ylmethoxy), and {6'-[2-(9,9-di-n-hexylfluorenyl)]pyrid-3'-ylmethoxy} substituents, respectively. They were obtained by 3-fold reactions of 2-[4-(bromomethyl)phenyl]pyridine (3), 5-(bromomethyl)-2-phenylpyridine (8), and 5-(bromomethyl)-2-(9,9-di-n-hexylfluorenyl)pyridine (13) with the 1,3,5-trimethylether of the t-Bu-calix[6]arene in the presence of sodium hydride in THF in 56-75% yields. Detailed analysis of the 1H NMR spectra (including variable-temperature data for 4) has established that 4, 9, and 14 exist predominantly in the C3v cone conformation with minor Cs isomers also observed. The X-ray crystal structure of 4 reveals two molecules of similar cone conformation, with all three 4'-(pyrid-2' '-yl)phenylmethoxy substituents stretched in the axial direction. Molecule I has a dimeric capsule structure with (pyrid-2' '-yl)phenylmethoxy substituents of one molecule interpenetrating those of its inversion equivalent to form a deep enclosed intermolecular cavity, which contains a CH2Cl2 guest molecule. Molecule II forms no such pair: the intramolecular cavity is filled with solvent molecules.
authors.affiliation: Department of Chemistry, Durham University, Durham DH1 3LE, UK.
authors.forename: Xianshun
authors.initials: X
authors.lastname: Zeng
authors.forename: Andrei S
authors.initials: AS
authors.lastname: Batsanov
authors.forename: Martin R
authors.initials: MR
authors.lastname: Bryce
mesh_terms: D047250:Calixarenes / Q000138:chemical synthesis* / Q000737:chemistry; D018360:Crystallography, X-Ray; D005449:Fluorenes / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D010636:Phenols / Q000138:chemical synthesis* / Q000737:chemistry; D011725:Pyridines / Q000737:chemistry*; D012680:Sensitivity and Specificity
chemical_list: D005449:Fluorenes; D010636:Phenols; D011725:Pyridines; C476540:calix(6)arene; D047250:Calixarenes; C058324:2-phenylpyridine