Recent advances in the synthesis of well-defined glycopolymers

Glycopolymers are receiving increasing interest due to their application in areas, such as glycomics, medicine, biotechnology, sensors, and separation science. Consequently, new methods for their synthesis are constantly being developed, with an increasing emphasis on the preparation of well-defined polymers and on the production of complex macromolecular architectures such as stars. This review covers recent developments in the synthesis of glycopolymers, with a particular emphasis on (i) the use of controlled radical polymerization to prepare well-defined glycopolymers from unprotected monomers and (ii) postpolymerization modification strategies using reactive polymer precursors (including “click” reactions). Recent work on the production of glycosylated polypeptides, which are under investigation as mimics of naturally occurring glycoproteins, is also included. The authors offer some suggestions as to future developments and remaining challenges in this topical area of polymer chemistry. © 2007 Wiley Periodicals, Inc. J Polym Sci PartA: Polym Chem45: 2059–2072, 2007     

Enantioselective synthesis of epoxides by alpha-deprotonation--electrophile trapping of achiral epoxides

Enantioselective alpha-deprotonation of achiral epoxides 1, 21, and 26 using organolithiums in the presence of (-)-sparteine 2 and subsequent electrophile trapping gives access to enantioenriched trisubstituted epoxides 9-17, 22, 23, 27 and 28 (in up to 86% ee).     

Das Reaktionsverhalten von Cp2NbCl2 gegenüber WF6—Struktur von [Cp2NbCl2]4[WF6]2[WCl6]

The oxidation of Cp₂NbCl₂ with pure WF₆ in SO₂ solution yielded the cationic metallocene species [Cp₂NbCl₂]⁺[WF₆]⁻ essentially in quantitative yield. The same reaction carried out in the presence of either equimolar amounts or a two-fold excess of HCN led to the preparation of the new niobocenium salt [Cp₂NbCl₂]₄⁺[WF₆]²⁻ which was studied by single crystal X-ray diffraction. This compound represents the first example of a structurally characterized metallocene-WF₆⁻ complex, and crystallizes in the tetragonal system: space group, P4₁2₁2(No. 92), a = 11.083(8) Å, c = 48.285 (9) Å; Z = 8; R = 0.0759, R_W = 0.0841. ab]Die Oxidation von Cp₂NbCl₂ mit reinem WF₆ führt in SO₂-Lösung zur Synthese von [Cp₂NbCl₂ ]⁺[WF₆]⁻ in nahezu quantitativer Ausbeute. Die analoge Reaktion führt unter Anwesenheit der äquimolaren Menge oder eines zweifachen Überschusses an HCN zur Ausbildung des Niobocenium-Komplexsalzes [Cp₂NbCl₂]₄⁺ [WF₆]₂⁻[WCl₆]²⁻, von dem eine Röntgenstrukturanalyse angefertigt wurde. Diese Verbindung repräsentiert den ersten structurell charakterisierten Vertreter eines Metallocen-WF₆⁻-Komplexes und kristallisiert im tetragonalen System: Raumgruppe P4₁2₁2 (Nr. 92), a = 11.083(8) Å, c = 48.285(9) Å; Z = 8; R = 0.0759, R_W = 0.0841. kw]Niobium; X-ray diffraction; Oxidation; Metallocenes     

Multi‐stage high order semi‐Lagrangian schemes for incompressible flows in Cartesian geometries

Efficient transport algorithms are essential to the numerical resolution of incompressible fluid‐flow problems. Semi‐Lagrangian methods are widely used in grid based methods to achieve this aim. The accuracy of the interpolation strategy then determines the properties of the scheme. We introduce a simple multi‐stage procedure, which can easily be used to increase the order of accuracy of a code based on multilinear interpolations. This approach is an extension of a corrective algorithm introduced by Dupont & Liu (2003, 2007). This multi‐stage procedure can be easily implemented in existing parallel codes using a domain decomposition strategy, as the communication pattern is identical to that of the multilinear scheme. We show how a combination of a forward and backward error correction can provide a third‐order accurate scheme, thus significantly reducing diffusive effects while retaining a non‐dispersive leading error term. Copyright © 2016 John Wiley & Sons, Ltd.     

Thionylimido Complexes

An improved route to d-block and main group NSO complexes is presented including the synthesis of the first antimony(V) complexes, (Ar₃Sb(NSO)₂), and copper examples [CuBipy(PPh₃)NSO]. The structures of eight complexes are reported. The observed variation in M–N–S bond angles is due to the combination of orbital overlap (ligand-to-metal bonding) and the degree of ionicity of the bonding.     

Nitrite reduction by copper through ligand-mediated proton and electron transfer

Nitrite reduction by a copper complex featuring a proton-responsive tripodal ligand is demonstrated. Gaseous nitric oxide was confirmed as the sole NO_X by-product in quantitative yield. DFT calculations predict that nitrite reduction occurs via a proton and electron transfer process mediated by the ligand. The reported mechanism parallels nitrite reduction by copper nitrite reductase.     

Relationships between molecular structure and thermomechanical properties of bio‐based thermosetting polymers

Molecular dynamics simulations are used to study highly cross‐linked epoxy networks comprised of furanyl epoxy monomer, 2,5‐bis[(2‐oxiranylmethoxy)methyl]‐furan (BOF), that is cross‐linked by two furanyl amine hardeners, 5,5'‐methylenedifurfurylamine (DFDA) and 5,5'‐ethylidenedifurfirylamine (CH₃‐DFDA). Important properties of these fully furan‐based systems, including room temperature density, glass transition temperature, and Young's modulus are found to agree with previous experimental results. We also compare the simulated and experimental values of four fully furan‐based thermosetting materials to those using the conventional resin diglycidyl ether of bisphenol A (DGEBA) cured with the two furanyl hardeners. Our simulation results predict a slight decrease in density and Young's modulus, but no impact on the glass transition temperature, upon adding the methyl group in DFDA. Detailed analyses of the MD trajectories reveal the underlying mechanisms responsible for the observed structure/property relations, which center on the lack of collinear covalent bonds in the BOF molecular structure. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 285–292