title: Conformation analyses, dynamic behavior, and amide bond distortions of medium-sized heterocycles. 2. Partially and fully reduced 1-benzazocines, benzazonines, and benzazecines.
abstract: Partially and fully reduced forms of benzo-fused eight- to ten-membered nitrogen heterocycles (1-benzazecines, 1-benzazonines and 1-benzazecines) have been prepared. Conformational features, transannular distances and dynamic behavior were studied using X-ray crystallography and VT NMR spectroscopy. The amide moiety in the nine-membered benzazonine ring 5b favors N-pyramidization, whereas the ten-membered benzazecine 5c adopts an amide twist. Molecular mechanics calculations reveals a correlation between the amide twist (tau) and ring stability. The dynamic behavior of the heterocycles in solution were also found to be dependent on the extent and nature of the amide distortion. We thus conclude that ring strain of these medium-sized heterocyclic rings is relieved through amide distortion, which leads to a more stable structure.
authors.affiliation: Department of Chermistry, King's College London, Strand WC2R 2LS, UK.
authors.forename: Maryiam
authors.initials: M
authors.lastname: Qadir
authors.forename: Jonathan
authors.initials: J
authors.lastname: Cobb
authors.forename: Peter W
authors.initials: PW
authors.lastname: Sheldrake
authors.forename: Neil
authors.initials: N
authors.lastname: Whittall
authors.forename: Andrew J P
authors.initials: AJ
authors.lastname: White
authors.forename: King Kuok Mimi
authors.initials: KK
authors.lastname: Hii
authors.forename: Peter N
authors.initials: PN
authors.lastname: Horton
authors.forename: Michael B
authors.initials: MB
authors.lastname: Hursthouse
mesh_terms: D000577:Amides / Q000737:chemistry*; D001391:Azo Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D001392:Azocines / Q000138:chemical synthesis* / Q000737:chemistry*; D018360:Crystallography, X-Ray; D003500:Cyclization; D006574:Heterocyclic Compounds, 2-Ring / Q000138:chemical synthesis / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D013329:Structure-Activity Relationship; D013696:Temperature
chemical_list: D000577:Amides; D001391:Azo Compounds; D001392:Azocines; D006574:Heterocyclic Compounds, 2-Ring