title: Regiospecifically Fluorinated Polycyclic Aromatic Hydrocarbons via Julia-Kocienski Olefination and Oxidative Photocyclization. Effect of Fluorine Atom Substitution on Molecular Shape.
abstract: A modular synthesis of regiospecifically fluorinated polycyclic aromatic hydrocarbons (PAHs) is described. 1,2-Diarylfluoroalkenes, synthesized via Julia-Kocienski olefination (70-99% yields), were converted to isomeric 5- and 6-fluorobenzo[c]phenanthrene, 5-and 6-fluorochrysene, and 9- and 10-benzo[g]chrysene (66-83% yields) by oxidative photocyclization. Photocyclization to 6-fluorochrysene proceeded more slowly than conversion of 1-styrylnaphthalene to chrysene. Higher fluoroalkene dilution led to a more rapid cyclization. Therefore, photocyclizations were performed at higher dilutions. To evaluate the effect of fluorine atom on molecular shapes, X-ray data for 5- and 6-fluorobenzo[c]phenanthrene, 6-fluorochrysene, 9- and 10-fluorobenzo[g]chrysene, and unfluorinated chrysene as well as benzo[g]chrysene were obtained and compared. The fluorine atom caused a small deviation from planarity in the chrysene series and decreased nonplanarity in the benzo[c]phenanthrene derivatives, but its influence was most pronounced in the benzo[g]chrysene series. A remarkable flattening of the molecule was observed in 9-fluorobenzo[g]chrysene, where the short 2.055 Å interatomic distance between bay-region F-9 and H-8, downfield shift of H-8, and a 26.1 Hz coupling between F-9 and C-8 indicate a possible F-9···H-8 hydrogen bond. In addition, in 9-fluorobenzo[g]chrysene, the stacking distance is short at 3.365 Å and there is an additional interaction between the C-11-H and C-10a of a nearby molecule that is almost perpendicular.
authors.affiliation: Department of Chemistry, The City College of New York , 160 Convent Avenue, New York, New York 10031, United States.
authors.forename: Shaibal
authors.initials: S
authors.lastname: Banerjee
authors.affiliation: Department of Chemistry, The City College of New York , 160 Convent Avenue, New York, New York 10031, United States.
authors.forename: Saikat
authors.initials: S
authors.lastname: Sinha
authors.affiliation: Department of Chemistry, The City College of New York , 160 Convent Avenue, New York, New York 10031, United States.
authors.forename: Padmanava
authors.initials: P
authors.lastname: Pradhan
authors.affiliation: Department of Chemistry, Vassar College , Poughkeepsie, New York 12604, United States.
authors.forename: Alessio
authors.initials: A
authors.lastname: Caruso
authors.affiliation: Department of Chemistry, Vassar College , Poughkeepsie, New York 12604, United States.
authors.forename: Daniel
authors.initials: D
authors.lastname: Liebowitz
authors.affiliation: Naval Research Laboratory, Code 6030, 4555 Overlook Avenue, Washington, DC 20375, United States.
authors.forename: Damon
authors.initials: D
authors.lastname: Parrish
authors.affiliation: Department of Chemistry, Vassar College , Poughkeepsie, New York 12604, United States.
authors.forename: Miriam
authors.initials: M
authors.lastname: Rossi
authors.affiliation: Department of Chemistry, The City College of New York , 160 Convent Avenue, New York, New York 10031, United States.|The Ph.D. Program in Chemistry, The Graduate Center of The City University of New York , New York, New York 10016, United States.
authors.forename: Barbara
authors.initials: B
authors.lastname: Zajc
mesh_terms: D000475:Alkenes / Q000138:chemical synthesis; D003500:Cyclization; D005461:Fluorine / Q000737:chemistry*; D005466:Fluorocarbons / Q000138:chemical synthesis*; D008958:Models, Molecular; D008968:Molecular Conformation; D010084:Oxidation-Reduction; D010777:Photochemistry; D011084:Polycyclic Aromatic Hydrocarbons / Q000138:chemical synthesis*; D014961:X-Ray Diffraction
chemical_list: D000475:Alkenes; D005466:Fluorocarbons; D011084:Polycyclic Aromatic Hydrocarbons; D005461:Fluorine