118457-61-7Relevant articles and documents
Chiral Lewis Acid Catalysed Asymmetric Nucleophilic Ring Opening of Cyclohexene Oxide
Adolfsson, Hans,Moberg, Christina
, p. 2023 - 2032 (1995)
Titanium and zirconium complexes of bispicolinic amides catalyze the ring opening of cyclohexene oxide with trimethylsilyl azide as nucleophile.The product, 1-azido-2-trimethylsilyloxycyclohexane, was obtained in up to 71percent enantioselectivity when a catalyst prepared from (S,S)-N,N'-bis(2-pyridinecarboxamide)-1,2-diphenylethane and zirconium tetra-t-butoxide was employed under optimum conditions, which included the addition of a small amount of diethylamine in the catalyst preparation step.The nature of the catalyst is still unknown, but it seems probable that oligomeric metal species are involved.
Mechanistic Studies of the Zirconium-Triisopropanolamine-Catalyzed Enantioselective Addition of Azide to Cyclohexene Oxide
McCleland, Brent W.,Nugent, William A.,Finn
, p. 6656 - 6666 (1998)
The mechanism of the enantioselective ring-opening of cyclohexene oxide by Me3SiN3, catalyzed by zirconium complexes of the C3-symmetric ligand (+)-(S,S,S)-triisopropanolamine, has been investigated. Measurements of molecu
Chiral Chromium Salen@rGO as Multipurpose and Recyclable Heterogeneous Catalyst
Abd El Sater, Mariam,Mellah, Mohamed,Dragoe, Diana,Kolodziej, Emilie,Jaber, Nada,Schulz, Emmanuelle
supporting information, p. 9454 - 9460 (2021/05/26)
The first immobilization of a pyrene-tagged chromium salen complex through π-π noncovalent interactions on reduced graphene oxide (rGO) is described. A very robust supported catalytic system is obtained to promote asymmetric catalysis in repeated cycles, without loss of activity or enantioselectivity. This specific behavior was demonstrated in two different catalytic reactions (up to ten reuses) promoted by chromium salen complexes, the cyclohexene oxide ring-opening reaction and the hetero-Diels-Alder cycloaddition between various aldehydes and Danishefsky's diene. Furthermore, the chiral chromium salen@rGO has been found to be compatible with a multi-substrate type use, in which the structure of the substrate involved is modified each time the catalyst is reused.
Helix-forming propensity of aliphatic urea oligomers incorporating noncanonical residue substitution patterns
Pendem, Nagendar,Douat, Celine,Claudon, Paul,Laguerre, Michel,Castano, Sabine,Desbat, Bernard,Cavagnat, Dominique,Ennifar, Eric,Kauffmann, Brice,Guichard, Gilles
supporting information, p. 4884 - 4892 (2013/05/09)
Aliphatic N,N′-linked oligoureas are peptidomimetic foldamers that adopt a well-defined helical secondary structure stabilized by a collection of remote three-center H-bonds closing 12- and 14-membered pseudorings. Delineating the rules that govern helix formation depending on the nature of constituent units is of practical utility if one aims to utilize this helical fold to place side chains in a given arrangement and elaborate functional helices. In this work, we tested whether the helix geometry is compatible with alternative substitution patterns. The central -NH-CH(R)-CH2-NH-CO- residue in a model oligourea pentamer sequence was replaced by guest units bearing various substitution patterns [e.g., -NH-CH2-CH2-NH-CO-, -NH-CH2-CH(R)-NH-CO-, and -NH-CH(R1)-CH(R 2)-NH-CO-], levels of preorganization (cyclic vs acyclic residues), and stereochemistries, and the helix formation was systematically assessed. The extent of helix perturbation or stabilization was primarily monitored in solution by Fourier transform IR, NMR, and electronic circular dichroism spectroscopies. Our results indicate that although three new substitution patterns were accommodated in the 2.5-helix, the helical urea backbone in short oligomers is particularly sensitive to variations in the residue substitution pattern (position and stereochemistry). For example, the trans-1,2- diaminocyclohexane unit was experimentally found to break the helix nucleation, but the corresponding cis unit did not. Theoretical calculations helped to rationalize these results. The conformational preferences in this series of oligoureas were also studied at high resolution by X-ray structure analyses of a representative set of modified oligomers.
New chiral calixsalen chromium complexes: Recyclable asymmetric catalysts
Zulauf, Anais,Mellah, Mohamed,Schulz, Emmanuelle
experimental part, p. 11108 - 11114 (2010/11/16)
A chiral N,N'-bis(salicylidene)ethylenediamine (salen) polymer has been prepared by a condensation reaction between a thio-phenedisalicyladehyde derivative and (S,S)-cyclohexane-1,2-diamine. This polymeric compound was demonstrated to possess a cyclic structure with two to five repetitive units. The addition of chromium(II) salts led to the generation of a chiral catalyst that could be recovered as an insoluble powder. The performance of this new calixsalen-type catalyst was examined in various transformations, particularly in its ability to promote nucleophilic epoxide ring opening under heterogeneous conditions. The target products were obtained in high yields and with improved selectivity compared with those obtained by using analogous linear polymers. The arrangement of the catalytic sites in the cyclic structure is probably more suitable for the necessary cooperative bimetallic pathway of this demanding reaction. The catalyst could be successfully recycled. This approach represents the first use of calixsalen complexes under heterogeneous catalytic conditions.
