title: Nonplanar aromatic compounds. 5. A atrategy for the synthesis of cis-10b,10c-dimethyl-10b,10c-dihydropyrenes. First crystal structure of a cis-10b,10c-dimethyl-10b,10c-dihydropyrene.
abstract: Through the use of a potentially removable tether, a heavily substituted 10b,10c-dimethyl-10b,10c-dihydropyrene (DMDHP), 20, was synthesized exclusively as the cis-isomer. It exists as the major component (20:1) in an equilibrium with its valence isomer syn-[2.2]metacyclophanediene 19. An X-ray crystal structure determination of 20, a cis-(2,7)-10b,10c-dihydropyrenophane, provided the first experimental measurements of the cis-DMDHP skeleton. The observed bond alternation in the [14]annulene was found to be larger than that of the corresponding trans-DMDHP framework. Prior MMPI calculations, on which previous discussion of the structure of the cis-DMDHP system had been based, are in very good agreement with the experimental results. Our own DFT calculations predict a more symmetric and more bond equalized structure than was observed in 20.
authors.affiliation: Department of Chemistry, Memorial University of Newfoundland, St. John's, NF, Canada A1B 3X7. gbodwell@mun.ca
authors.forename: G J
authors.initials: GJ
authors.lastname: Bodwell
authors.forename: J N
authors.initials: JN
authors.lastname: Bridson
authors.forename: S L
authors.initials: SL
authors.lastname: Chen
authors.forename: R A
authors.initials: RA
authors.lastname: Poirier