title: Substituted Diarylnorbornadienes and Quadricyclanes: Synthesis, Photochemical Properties, and Effect of Substituent on the Kinetic Stability of Quadricyclanes.
abstract: In this Article, we present a new method for the synthesis of diarylnorbornadiene derivatives. Through the use of a two-step procedure consisting of a tandem alkene insertion-Suzuki coupling reaction followed by a DDQ dehydrogenation, we have been able to synthesize derivatives with a wide variety of substituents. We also present the results of UV-visible spectroscopy studies and kinetics experiments that show the effect of substituent on light absorption properties of the norbornadienes as well as the kinetic stability of the quadricyclanes that result from their photochemical conversion. While substitution on the aromatic rings had comparatively little effect on quadricyclane lability, substitution at a bridgehead position with a methyl group produced a quadricyclane that thermally reverted to the norbornadiene at a rate that was significantly slower than that for the quadricyclane without the methyl substituent. From the results of the kinetics experiments, we determined that the reversion of the quadricyclanes occurs via a free radical mechanism with very little contribution from polar effects. This observation led us to speculate as to whether our data may form the basis for a free radical substituent constant, σQ•, analogous to the traditional Hammett σ parameter.
authors.affiliation: Department of Chemistry, West Chester University of Pennsylvania , West Chester, Pennsylvania 19383, United States.
authors.forename: Kyle J
authors.initials: KJ
authors.lastname: Spivack
authors.affiliation: Department of Chemistry, West Chester University of Pennsylvania , West Chester, Pennsylvania 19383, United States.
authors.forename: Jesse V
authors.initials: JV
authors.lastname: Walker
authors.affiliation: Department of Chemistry, West Chester University of Pennsylvania , West Chester, Pennsylvania 19383, United States.
authors.forename: Maria J
authors.initials: MJ
authors.lastname: Sanford
authors.affiliation: Department of Chemistry, West Chester University of Pennsylvania , West Chester, Pennsylvania 19383, United States.
authors.forename: Benjamin R
authors.initials: BR
authors.lastname: Rupert
authors.affiliation: Department of Chemistry, West Chester University of Pennsylvania , West Chester, Pennsylvania 19383, United States.
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Ehle
authors.affiliation: Department of Chemistry, West Chester University of Pennsylvania , West Chester, Pennsylvania 19383, United States.
authors.forename: James M
authors.initials: JM
authors.lastname: Tocyloski
authors.affiliation: Department of Chemistry, West Chester University of Pennsylvania , West Chester, Pennsylvania 19383, United States.
authors.forename: Aaron N
authors.initials: AN
authors.lastname: Jahn
authors.affiliation: Department of Chemistry, West Chester University of Pennsylvania , West Chester, Pennsylvania 19383, United States.
authors.forename: Lyndsey M
authors.initials: LM
authors.lastname: Shaak
authors.affiliation: Department of Chemistry, West Chester University of Pennsylvania , West Chester, Pennsylvania 19383, United States.
authors.forename: Obiamaka
authors.initials: O
authors.lastname: Obianyo
authors.affiliation: Department of Chemistry, West Chester University of Pennsylvania , West Chester, Pennsylvania 19383, United States.
authors.forename: Karyn M
authors.initials: KM
authors.lastname: Usher
authors.affiliation: Department of Chemistry, West Chester University of Pennsylvania , West Chester, Pennsylvania 19383, United States.
authors.forename: Felix E
authors.identifier: 0000-0002-9046-4671
authors.initials: FE
authors.lastname: Goodson