title: Enyne [4 + 4] photocycloaddition: bridged 1,2,5-cyclooctatrienes.
abstract: Enyne photocycloaddition with a 2-pyridone yields a mixture of products including amide-bridged 1,2,5-cyclooctatrienes, the first examples of enyne [4 + 4] adducts. Four regio- and stereochemical isomers of the [4 + 4] adduct are possible. All appear to be too strained to be isolated, but they have been identified as their [2 + 2] cyclobutane dimers. Cyclobutane and cyclobutene adducts have also been isolated, [2 + 2] addition products possibly related to the unstable [4 + 4] adducts via Cope rearrangement. Calculations suggest that [3,3] rearrangements have high energy barriers, however, making thermal interconversion unlikely.
authors.affiliation: Department of Chemistry, Temple University, 1901 N. 13th Street, Philadelphia, Pennsylvania 19122, USA.
authors.forename: Svitlana
authors.initials: S
authors.lastname: Kulyk
authors.forename: William G
authors.initials: WG
authors.lastname: Dougherty
authors.forename: W Scott
authors.initials: WS
authors.lastname: Kassel
authors.forename: Steven A
authors.initials: SA
authors.lastname: Fleming
authors.forename: Scott McN
authors.initials: SM
authors.lastname: Sieburth