title: Intramolecular pyridone/enyne photocycloaddition: partitioning of the [4 + 4] and [2 + 2] pathways.
abstract: Intramolecular photocycloaddition (>290 nm) between a 1,3-enyne and a 2-pyridone is far more selective than the intermolecular version; a three-atom linkage both controls regiochemistry and separates the [2 + 2] and [4 + 4] pathways. All four head-to-head, head-to-tail, tail-to-head, and tail-to-tail tetherings have been investigated. Linkage via the ene of the enyne leads to [2 + 2] products regardless of alkene geometry, whereas linkage through the yne results in [4 + 4] cycloadducts. The bridged 1,2,5-cyclooctatriene products of [4 + 4] cycloaddition are unstable and undergo a subsequent [2 + 2] dimerization reaction.
authors: Department of Chemistry, Temple University, 1901 North 13th Street, Philadelphia, Pennsylvania 19122, United States.
authors: Svitlana
authors: S
authors: Kulyk
authors: William G
authors: WG
authors: Dougherty
authors: W Scott
authors: WS
authors: Kassel
authors: Michael J
authors: MJ
authors: Zdilla
authors: Scott McN
authors: SM
authors: Sieburth