title: Diazadithia[7]helicenes: Synthetic Exploration, Solid-State Structure, and Properties.
abstract: Diazadithia[7]helicenes were synthesized from the readily available building block ethyl 7-chloro-8-formylthieno[3,2-f]quinoline-2-carboxylate by a Wittig reaction-photocyclization strategy. The helicene core was functionalized by nucleophilic aromatic substitution with a variety of nucleophiles (e.g., O-, N-, and C-centered) and palladium-catalyzed reactions such as Suzuki coupling and Buchwald-Hartwig amination. Racemization studies confirmed that the enantiopure forms of these [7]helicenes are conformationally stable compared to their lower analogues. The solid-state structures of the novel diazadithia[7]helicenes were determined by single-crystal X-ray diffraction. The crystal structures of these azathia[7]helicenes show columnar stacking in antiparallel fashion. The HOMO-LUMO gaps of the new compounds were determined on the basis of electrochemical and optical measurements.
authors.affiliation: Molecular Design and Synthesis, Department of Chemistry, KU Leuven, Celestijnenlaan 200F, 3001 Leuven (Belgium), Fax: (+32) 16327990.
authors.forename: Deepali
authors.initials: D
authors.lastname: Waghray
authors.forename: Arvid
authors.initials: A
authors.lastname: Cloet
authors.forename: Kristof
authors.initials: K
authors.lastname: Van Hecke
authors.forename: Stijn F L
authors.initials: SF
authors.lastname: Mertens
authors.forename: Steven
authors.initials: S
authors.lastname: De Feyter
authors.forename: Luc
authors.initials: L
authors.lastname: Van Meervelt
authors.forename: Mark
authors.initials: M
authors.lastname: Van der Auweraer
authors.forename: Wim
authors.initials: W
authors.lastname: Dehaen
mesh_terms: D000586:Amination; D001372:Aza Compounds / Q000737:chemistry*; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D008968:Molecular Conformation; D010165:Palladium / Q000737:chemistry; D011083:Polycyclic Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D011804:Quinolines / Q000737:chemistry*; D060327:Solid-Phase Synthesis Techniques; D013237:Stereoisomerism
chemical_list: D001372:Aza Compounds; D011083:Polycyclic Compounds; D011804:Quinolines; C000600411:ethyl 7-chloro-8-formylthieno(3,2-f)quinoline-2-carboxylate; C031660:helicenes; D010165:Palladium
keywords: Wittig reactions; chiral resolution; cyclization; helical structures; helicenes