title: Hydrophobic Encapsulated Phosphonium Salts-Synthesis of Weakly Coordinating Cations and their Application in Wittig Reactions.
abstract: Large and rigid tetraarylphosphonium tetrafluoroborate salts have been synthesized representing weakly coordinating cations with diameters of several nanometers. Divergent dendritic growth by means of thermal Diels-Alder cycloaddition was employed for the construction of the hydrophobic polyphenylene framework up to the third generation. X-ray crystal structure analysis of first-generation phosphonium tetrafluoroborate supported the rigidity of the non-collapsible shell around the phosphorus center and gave insight into solid-state packing and cation-anion distances. Copper(I)-catalyzed azide-alkyne ligation served as reliable method for the preparation of a first-generation triazolylphenyl hybrid phosphonium cation under mild reaction conditions. Furthermore, from the synthesis of triarylbenzylphosphonium bromides, Wittig precursors with unprecedented bulky substituents in the α-position were accessible. Employment of these precursors under Wittig conditions by treatment with base and subsequent reaction with aldehydes preferentially provided (Z)-olefins with bulky polyphenylene substituents.
authors.affiliation: Max Planck Institute for Polymer Research, 55128 Mainz, Ackermannweg 10 (Germany).
authors.forename: Ralf
authors.initials: R
authors.lastname: Moritz
authors.affiliation: Max Planck Institute for Polymer Research, 55128 Mainz, Ackermannweg 10 (Germany).
authors.forename: Manfred
authors.initials: M
authors.lastname: Wagner
authors.affiliation: Institute of Organic Chemistry, University of Mainz, 55128 Mainz (Germany).
authors.forename: Dieter
authors.initials: D
authors.lastname: Schollmeyer
authors.affiliation: Max Planck Institute for Polymer Research, 55128 Mainz, Ackermannweg 10 (Germany).
authors.forename: Martin
authors.initials: M
authors.lastname: Baumgarten
authors.affiliation: Max Planck Institute for Polymer Research, 55128 Mainz, Ackermannweg 10 (Germany). muellen@mpip-mainz.mpg.de.
authors.forename: Klaus
authors.initials: K
authors.lastname: Müllen
keywords: Wittig reactions; phosphonium salts; phosphorus; polyphenylene olefins; weakly coordinating cations; ylides