title: Hairpin Furans and Giant Biaryls.
abstract: The thermal reaction of two cyclopentadienones with 5,5'-binaphthoquinone or 6,6'-dimethoxy-5,5'-binaphthoquinone in refluxing nitrobenzene (210 °C) gives, in a single synthetic step that includes two Diels-Alder additions, two decarbonylations, and two dehydrogenations, giant biaryl bisquinones (compounds 13, 14, 15, 18, and 21). However, when two cyclopentadienones react with 6,6'-dimethoxy-5,5'-binaphthoquinone in nitrobenzene at higher temperatures (250-260 °C), the resulting products are molecular ribbons composed of two twisted aromatic systems fused to a heteropentahelicene (19, 20, and 22). These molecules are representatives of a new class of chiral polycyclic aromatic compounds, the "hairpin furans". Interestingly, reheating a dimethoxy-substituted giant biaryl (e.g., 21) in nitrobenzene at 260 °C does not yield the corresponding hairpin furan (22), and mechanistic studies indicate that some intermediate or byproduct of the synthesis of the giant biaryls is a reagent or catalyst necessary for the conversion of the dimethoxybiaryl to the furan.
authors.affiliation: Department of Chemistry, Tulane University , New Orleans, Louisiana 70118, United States.
authors.forename: Xin
authors.initials: X
authors.lastname: Geng
authors.affiliation: Department of Chemistry, Tulane University , New Orleans, Louisiana 70118, United States.
authors.forename: Joel T
authors.initials: JT
authors.lastname: Mague
authors.affiliation: Department of Chemistry, Tulane University , New Orleans, Louisiana 70118, United States.
authors.forename: James P
authors.initials: JP
authors.lastname: Donahue
authors.affiliation: Department of Chemistry, Tulane University , New Orleans, Louisiana 70118, United States.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Pascal