title: Dynamic covalent approach to [2]- and [3]roxtanes by utilizing a reversible thiol-disulfide interchange reaction.
abstract: A dynamic covalent approach to disulfide-containing [2]- and [3]rotaxanes is described. Symmetrical dumbbell-shaped compounds with two secondary ammonium centers and a central located disulfide bond were synthesized as components of rotaxanes. The rotaxanes were synthesized from the dumbbell-shaped compounds and dibenzo-[24]crown-8 (DB24C8) with catalysis by benzenethiol. The yields of isolated rotaxanes reached about 90 % under optimized conditions. A kinetic study on the reaction forming [2]rotaxane 2 a and [3]rotaxane 3 a suggested a plausible reaction mechanism comprising several steps, including 1) initiation, 2) [2]rotaxane formation, and 3) [3]rotaxane formation. The whole reaction was found to be reversible in the presence of thiols, and thermodynamic control over product distribution was thus possible by varying the temperature, solvent, initial ratio of substrates, and concentration. The steric bulk of the end-capping groups had almost no influence on rotaxane yields, but the structure of the thiol was crucial for reaction rates. Amines and phosphines were also effective as catalysts. The structural characterization of the rotaxanes included an X-ray crystallographic study on [3]rotaxane 3 a.
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, Sakai, Japan.
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Furusho
authors.forename: Tomoya
authors.initials: T
authors.lastname: Oku
authors.forename: Toshihide
authors.initials: T
authors.lastname: Hasegawa
authors.forename: Akiyoshi
authors.initials: A
authors.lastname: Tsuboi
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Kihara
authors.forename: Toshikazu
authors.initials: T
authors.lastname: Takata
mesh_terms: D018360:Crystallography, X-Ray; D004220:Disulfides / Q000138:chemical synthesis* / Q000737:chemistry; D004988:Ethers, Cyclic / Q000737:chemistry; D006571:Heterocyclic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D011083:Polycyclic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D043862:Rotaxanes; D016339:Spectrometry, Mass, Fast Atom Bombardment; D013438:Sulfhydryl Compounds / Q000737:chemistry*
chemical_list: D004220:Disulfides; D004988:Ethers, Cyclic; D006571:Heterocyclic Compounds; D011083:Polycyclic Compounds; D043862:Rotaxanes; D013438:Sulfhydryl Compounds