title: Catalytic Oxidative Cyclization of 2'-Arylbenzaldehyde Oxime Ethers under Photoinduced Electron Transfer Conditions.
abstract: A series of 2'-arylbenzaldehyde oxime ethers were synthesized and shown to generate the corresponding phenanthridines upon irradiation in the presence of 9,10-dicyanoanthracene in acetonitrile. Mechanistic studies suggest that the oxidative cyclization reaction sequence is initiated by an electron transfer step followed by nucleophilic attack of the aryl ring onto the nitrogen of the oxime ether. A concave downward Hammett plot is presumably the result of a change in charge distribution in the radical cation species with strongly electron-donating substituents that yields a less electrophilic nitrogen atom and a decreased amount of cyclized product. The reaction is selective (no nitrile byproduct is formed unlike other photochemical reactions involving aldoxime ethers) as well as regiospecific when using 2'-aryl groups with meta-substituents, making this reaction a useful alternative for preparing substituted phenanthridines.
authors.affiliation: Department of Chemistry and Biochemistry, California State University, Fullerton, California 92834-6866, United States.
authors.forename: Julie L
authors.initials: JL
authors.lastname: Hofstra
authors.affiliation: Department of Chemistry and Biochemistry, California State University, Fullerton, California 92834-6866, United States.
authors.forename: Brittany R
authors.initials: BR
authors.lastname: Grassbaugh
authors.affiliation: Department of Chemistry and Biochemistry, California State University, Fullerton, California 92834-6866, United States.
authors.forename: Quan M
authors.initials: QM
authors.lastname: Tran
authors.affiliation: Department of Chemistry and Biochemistry, California State University, Fullerton, California 92834-6866, United States.
authors.forename: Nicholas R
authors.initials: NR
authors.lastname: Armada
authors.affiliation: Department of Chemistry and Biochemistry, California State University, Fullerton, California 92834-6866, United States.
authors.forename: H J Peter
authors.initials: HJ
authors.lastname: de Lijser