Selective and tuneable recognition of anions using C(3v)-symmetrical tripodal urea-amide receptor platforms

The synthesis and binding investigations of first generation C(3v)-symmetrical hydrogen bonding urea-amide based tripodal receptors, 1-6, with various anions such as acetate, phosphate, sulfate and chloride in DMSO-d(6) are presented. Analysis of the (1)H NMR titrations of 1-6 showed on all occasions the selective formation of 1?:?1 stoichiometries.     

The Mechanism of CO2 Insertion into Iridium(I) Hydroxide and Alkoxide Bonds: A Kinetics and Computational Study

The facile insertion of CO₂ into iridium(I) hydroxide, alkoxide, and amide bonds was recently reported. In particular, [Ir(cod)(IiPr)(OH)] (IiPr=1,3‐bis(isopropyl)imidazol‐2‐ylidene) reacted with CO₂ in solution and in the solid state in a matter of minutes to give the novel [{Ir(cod)(IiPr)}₂(μ‐κ¹O:κ²O,O‐CO₃)] complex. In the present study, this reaction is probed using kinetics and theoretical studies, which enabled us to analyse its facile nature and to fully elucidate the reaction mechanism with excellent correlation between the two methods.     

Catalytic asymmetric carbon–carbon bond forming reactions catalyzed by tetrahydroisoquinoline (TIQ) N,N′-dioxide ligands

The use of TIQ-N,N′-dioxide ligands in asymmetric C–C bond forming reactions is described. In the Michael addition of cyclohexane-1,3-dione and malonates to β,γ-unsaturated α-ketoesters, excellent yields (up to 93%) and moderate to good enantioselectivities (70–89% ee) were obtained. The catalytic hetero-ene reaction of 2-methoxypropene with phenylglyoxal gave the ene product in excellent yield (95%) with moderate enantioselectivity (77% ee). The catalyst system performed well at temperatures ranging from 0 to 30 °C and relatively low catalyst loading (0.2–5 mol %) with dichloromethane being the preferred solvent for all reactions.     

Cu(OAc)2 promoted Chan–Evans–Lam C–N cross coupling reactions on the N- and N′-nitrogen atoms of sulfonimidamides with aryl boronic acids

We report a highly efficient and mild protocol for Chan–Evans–Lam C–N cross coupling of sulfonimidamides and aryl boronic acids using Cu(OAc)₂ as mediator, triethylamine (TEA) as base and acetonitrile as solvent. The reaction proceeds at room temperature and provides high to excellent yields for a variety of boronic acids, allowing N-arylation of both N-protected (N-amine nitrogen) and N-deprotected (N′-imine nitrogen) sulfonimidamides.     

Synthesis and NMR elucidation of novel pentacycloundecane‐based peptides

The synthesis and NMR elucidation of two novel pentacycloundecane (PCU)‐based peptides are reported. The PCU cage amino acids were synthesised as racemates and the incorporation of the cage amino acid with (S)‐natural amino acids produced diastereomeric peptides. The diastereomeric ‘cage’ peptides were separated using preparative HPLC and the NMR elucidation of these PCU containing peptides are reported for the first time. The ¹H and ¹³C NMR spectra showed series of overlapping signals of the cage skeleton and that of the peptide, making it extremely difficult to resolve the structure using one‐dimensional NMR techniques only. The use of two‐dimensional NMR techniques proved to be a highly effective tool in overcoming this problem. Copyright © 2010 John Wiley & Sons, Ltd.     

NMR elucidation of some ligands derived from the pentacycloundecane skeleton

The complete NMR elucidation of three novel pentacycloundecane (PCU)-derived ligands is reported. 2D NMR techniques are used to overcome the problem of major overlapping of methine signals on the cage skeleton. The compounds were synthesized as potential ligands to be used in asymmetric catalysis. They represent the first instance where aromatic moieties have been attached directly to the cage skeleton using lithiation techniques. The X-ray crystal structure of one of the ligands was obtained. The X-ray structure was helpful in determining the potential NOESY interactions within the set of molecules. For the other ligands a high level Density Functional Theory (DFT) optimization was performed [B3LYP/6-31+g(d)] to visualize possible NOE interactions. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

High pressure X-ray diffraction study of Fe2B

We report the results of a synchrotron based X-ray diffraction study of bct-Fe₂B under quasi-hydrostatic conditions from 0 to 50 GPa. Over this pressure range, no phase change or disproportionation has been observed. A weighted fit of the data to the Birch-Murnaghan equation of state yields a value of the bulk modulus, K, of 164±14 GPa and the first pressure derivative of the bulk modulus, K′, of 4.4±0.5. The compression is found to be anisotropic, with the a-axis being more incompressible than the c-axis.     

Error bounds and metric subregularity

Necessary and sufficient criteria for metric subregularity (or calmness) of set-valued mappings between general metric or Banach spaces are treated in the framework of the theory of error bounds for a special family of extended real-valued functions of two variables. A classification scheme for the general error bound and metric subregularity criteria is presented. The criteria are formulated in terms of several kinds of primal and subdifferential slopes.     

Modulation of Crystal Packing via the Tuning of Peripheral Functionality for a Family of Dinuclear Mesocates

A family of four novel pyrazinyl‐hydrazone based ligands have been synthesized with differing functionality at the 5‐position of the central aromatic ring. Previous work has shown such ligands to form dinuclear triple mesocates which pack to form hexagonal channels capable of gas sorption. The effect of the peripheral functionality of the ligand on the crystal packing was investigated by synthesizing complexes 1 to 4 which feature amino, bromo, iodo and methoxy substituents respectively. Complexes 1 to 3 crystallized in the same hexagonal space group P6₃/m and featured 1D channels. However, on closer inspection while the packing of 1 is mediated by hydrogen bonding interactions, the packing of complexes 2 and 3 are not, due to a subtlety different π–π stacking interaction enforced by the halogen substituent. The more bulky nature of the methoxy substituent of 4 results in the complex crystallizing in the triclinic space group P‐1, featuring an entirely different crystal packing.