title: 1,4-Addition of benzene to a dihydrocyclopent[a]indene diradical: synthesis and DFT study.
abstract: Photochemical cyclization of compound 1, a homoenediyne (-CCC=CCH2CC-) bearing two ethynylanthracene chromophores, yields two isomeric dihydrocyclopent[a]indene ring systems, spiro-fused to the 9-position of a 9,10-dihydroanthracene moiety. Evidence of a photochemically initiated diradical cyclization pathway is proposed on the basis of (i) hydrogen abstraction from reaction with 1,4-cyclohexadiene (1,4-CHD) and (ii) the observation of 1,4-addition of benzene (solvent). The reaction was further analyzed by a complete density functional theory (DFT) study, using an unrestricted approach (UBLYP) with a 6-31G* basis set for the open-shell triplet states of the reactants, products, and diradical intermediates to model the photochemical nature of observed transformation. A mechanism detailing the observed cyclization/addition reaction is proposed.
authors.affiliation: Department of Chemistry, University of California at Riverside, Riverside, California 92506-0403, USA. michael.marsella@ucr.edu
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Marsella
authors.forename: Kunsang
authors.initials: K
authors.lastname: Yoon
authors.forename: Samia
authors.initials: S
authors.lastname: Estassi
authors.forename: Fook S
authors.initials: FS
authors.lastname: Tham
authors.forename: Dan B
authors.initials: DB
authors.lastname: Borchardt
authors.forename: Binh H
authors.initials: BH
authors.lastname: Bui
authors.forename: Peter R
authors.initials: PR
authors.lastname: Schreiner
mesh_terms: D001554:Benzene / Q000138:chemical synthesis / Q000737:chemistry; D005609:Free Radicals / Q000138:chemical synthesis / Q000737:chemistry; D007192:Indenes / Q000138:chemical synthesis / Q000737:chemistry; D008956:Models, Chemical; D015394:Molecular Structure
chemical_list: D005609:Free Radicals; D007192:Indenes; D001554:Benzene