title: Stepwise synthesis and selective dimerisation of bis- and trisloop tetra-urea calix[4]arenes.
abstract: Tetra-urea calix[4]arenes substituted with four mono- or bisalkenyl residues have been converted into bis- or tetraloop compounds by intramolecular olefin metathesis, with use of a tetratosylurea calix[4]arene as template. The same strategy has now been used to synthesise trisloop compounds and bisloop compounds with adjacent loops, completing the series of the loop-containing tetra-urea derivatives. A tetra-urea calix[4]arene of the AABB type, where A stands for a bisalkenyl- and B for a monoalkenyl-substituted urea unit, was used as precursor for the three loops. It was easily synthesised from a tetraamino calix[4]arene in which two adjacent amino groups were Boc-protected. The ABCB-type precursor for the two adjacent loops was prepared through protection of two opposite amino functions with trityl groups. The capabilities of the novel macrocyclic tetra-ureas for the selective formation of hydrogen-bonded dimers were studied.
authors.affiliation: Abteilung Lehramt Chemie, Fachbereich Chemie, Pharmazie und Geowissenschaften, Johannes Gutenberg-Universität Mainz, Duesbergweg 10-14, Mainz, Germany. rudzevic@uni-mainz.de
authors.forename: Yuliya
authors.initials: Y
authors.lastname: Rudzevich
authors.forename: Yudong
authors.initials: Y
authors.lastname: Cao
authors.forename: Valentyn
authors.initials: V
authors.lastname: Rudzevich
authors.forename: Volker
authors.initials: V
authors.lastname: Böhmer
mesh_terms: D047250:Calixarenes / Q000138:chemical synthesis* / Q000737:chemistry; D019281:Dimerization; D009682:Magnetic Resonance Spectroscopy; D010636:Phenols / Q000138:chemical synthesis* / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization; D014508:Urea / Q000737:chemistry*
chemical_list: D010636:Phenols; C121325:calix(4)arene; D047250:Calixarenes; D014508:Urea