title: Synthesis of Ex(n)Box cyclophanes.
abstract: A rapid and efficient synthesis of the extended bipyridinium-based class of cyclophanes--that is, Ex(n)Box(4+) (n = 0-3), where n is the number of p-phenylene rings inserted between the pyridinium rings--is demonstrated, resulting in much higher yields of products along with a reduced output of oligomeric byproducts. Although each cyclophane can be synthesized readily without the use of a precise stoichiometric amount of template, ExBox(4+) can be prepared in 66% yield (following crystallization) using six equivalents of pyrene in a template-directed protocol. This new methodology has been employed to synthesize, in modest yield, a nearly 2.5 nm long cyclophane consisting of 12 aromatic rings.
authors.affiliation: Department of Chemistry, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States.
authors.forename: Jonathan C
authors.initials: JC
authors.lastname: Barnes
authors.forename: Michal
authors.initials: M
authors.lastname: Juríček
authors.forename: Nicolaas A
authors.initials: NA
authors.lastname: Vermeulen
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Dale
authors.forename: J Fraser
authors.initials: JF
authors.lastname: Stoddart