title: The effects of H-bonding and sterics on the photoreactivity of a trimethyl butyrophenone derivative.
abstract: The irradiation of ester 1 in methanol and chloroform does not yield any photoproducts, whereas the photolysis of 1 in dry argon-saturated benzene produces cyclobutanol 4, which is converted to lactone 5 by the addition of HCl. Laser-flash photolysis of ester 1 demonstrates that 1 undergoes intramolecular H-atom abstraction to form the biradical 2 (λ(max)∼ 310 nm, τ = 200 ns, benzene), which intersystem crosses to photoenols, Z-3 (λ(max)∼ 380 nm, τ = 30-60 μs, benzene) and E-3 (λ(max)∼ 380 nm, τ = 11 ms, benzene). Density functional theory calculations were performed to support the proposed mechanism for forming cyclobutanol 4 and to explain how steric demand facilitates photoenol E-3 to form cyclobutanol 4 rather than lactone 5.
authors.affiliation: Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221, USA.
authors.forename: Qian
authors.initials: Q
authors.lastname: Li
authors.forename: Jagadis
authors.initials: J
authors.lastname: Sankaranarayanan
authors.forename: Michael
authors.initials: M
authors.lastname: Hawk
authors.forename: Vivian T
authors.initials: VT
authors.lastname: Tran
authors.forename: Jessica L
authors.initials: JL
authors.lastname: Brown
authors.forename: Anna D
authors.initials: AD
authors.lastname: Gudmundsdottir