Base-catalyzed cross coupling of secondary alcohols and aryl-aldehydes with concomitant oxidation of alcohols to ketones: An alternative route for synthesis of the Claisen-Schmidt condensation products

Base-catalyzed C–C cross coupling of secondary alcohols and aryl-aldehydes was achieved, when an alcoholic solution of an aryl-aldehyde was stirred under reflux for 45 h in the presence of a catalytic (20 mol%) amount of K₂CO₃. The consistent formation of α,α′-bis-(benzylidene) alkanones was obtained in moderate to good yields using various secondary alcohols and substituted aryl-aldehydes. Herein, α,α′-bis-(benzylidene)alkanones, which are the classical products of Claisen-Schmidt (cross aldol) condensation, have been synthesized via an alternative strategy using secondary alcohols. Bis-(benzylidene) alkanones are an integral part of various drug regimes and the production of bis-(benzylidene) alkanones without using any precious metal is a major outcome of the present reaction.     

On the risk-based steam generator lifetime optimisation

A probabilistic fracture mechanics model is employed to estimate the failure probability of axially cracked steam generator tubes. The model estimates the failure probability from the random changes of the influencing parameters such as tube and crack geometry, material properties and non-destructive examination results, reliability and sizing accuracy and stable crack propagation. The performance of the model is illustrated by a numerical example. A steam generator tubing severely affected by the stress corrosion cracking is studied during most unfavourable accidental conditions. Two different plugging approaches are analyzed and the quality is compared, showing the superior performance of crack length oriented approach over tube wall thickness reduction both in terms of SG failure probability and extent of plugging. Thus, apart from setting the acceptable SG failure probability, all elements for the risk-based SG lifetime optimisation are provided on the example of stress corrosion cracking in the tube expansion transition zone.     

Light at the interface: the potential of attenuated total reflection infrared spectroscopy for understanding heterogeneous catalysis in water

IR spectroscopy has been an important tool for studying detailed interactions of reactants and reaction-intermediates with catalyst surfaces. Studying reactions in water is, however, far from trivial, due to the excessive absorption of infrared light by water. One way to deal with this is the use of Attenuated Total Reflection spectroscopy (ATR-IR) minimizing the path length of infrared light through the water. Moreover, ATR-IR allows for a direct comparison of reactions in gas and water on the same sample, which bridges the gap between separate catalyst investigations in gas and liquid phase. This tutorial review describes recent progress in using ATR-IR for studying heterogeneous catalysts in water. An overview is given of the important aspects to be taken into account when using ATR-IR to study heterogeneous catalysts in liquid phase, like the procedure to prepare stable catalyst layers on the internal reflection element. As a case study, CO adsorption and oxidation on noble metal catalysts is investigated with ATR-IR in gas and water. The results show a large effect of water and pH on the adsorption and oxidation of CO on Pt/Al(2)O(3) and Pd/Al(2)O(3). From the results it is concluded that water affects the metal particle potential as well as the adsorbed CO molecule directly, resulting in higher oxidation rates in water compared to gas phase. Moreover, also pH influences the metal particle potential with a clear effect on the observed oxidation rates. Finally, the future outlook illustrates that ATR-IR spectroscopy holds great promise in the field of liquid phase heterogeneous catalysis.     

Synthesis and characterization of [MCl2(nPr-N(Ph2P)2] (M?=?Pt, Pd) complexes and hydroformylation of 1-octene using [PtCl2(R-N(Ph2P)2)] (R?=?benzyl, 2-picolyl, nPr) complexes

The synthesis and characterization of platinum(II) and palladium(II) complexes of the type [PtX₂( ⁿ Pr-N(Ph₂P)₂)] (X = Cl, I) and [PdCl₂(R-N(Ph₂P)₂)] {R =  ⁿ Pr, p-OMe(C₆H₄)} containing aminodiphosphine P,P-bidentate ligands is described. Complexes of the type [PtCl₂(R-N(Ph₂P)₂)] (where R = benzyl, 2-picolyl and ⁿ Pr) catalyzed the hydroformylation of 1-octene, albeit at low activities and slightly elevated regioselectivities toward the linear aldehyde, when compared with analogous compounds containing small bite angles.     

A 93Nb Solid‐State NMR and Density Functional Theory Study of Four‐ and Six‐Coordinate Niobate Systems

A variable B₀ field static (broadline) NMR study of a large suite of niobate materials has enabled the elucidation of high‐precision measurement of ⁹³Nb NMR interaction parameters such as the isotropic chemical shift (δ_iso), quadrupole coupling constant and asymmetry parameter (C_Q and η_Q), chemical shift span/anisotropy and skew/asymmetry (Ω/Δδ and κ/η_δ) and Euler angles (α, β, γ) describing the relative orientation of the quadrupolar and chemical shift tensorial frames. These measurements have been augmented with ab initio DFT calculations by using WIEN2k and NMR‐CASTEP codes, which corroborate these reported values. Unlike previous assertions made about the inability to detect CSA (chemical shift anisotropy) contributions from Nb^V in most oxo environments, this study emphasises that a thorough variable B₀ approach coupled with the VOCS (variable offset cumulative spectroscopy) technique for the acquisition of undistorted broad (?1/2?+1/2) central transition resonances facilitates the unambiguous observation of both quadrupolar and CSA contributions within these ⁹³Nb broadline data. These measurements reveal that the ⁹³Nb electric field gradient tensor is a particularly sensitive measure of the immediate and extended environments of the Nb^V positions, with C_Q values in the 0 to >80 MHz range being measured; similarly, the δ_iso (covering an approximately 250 ppm range) and Ω values (covering a 0 to approximately 800 ppm range) characteristic of these niobate systems are also sensitive to structural disposition. However, their systematic rationalisation in terms of the Nb? O bond angles and distances defining the immediate Nb^V oxo environment is complicated by longer‐range influences that usually involve other heavy elements comprising the structure. It has also been established in this study that the best computational method(s) of analysis for the ⁹³Nb NMR interaction parameters generated here are the all‐electron WIEN2k and the gauge included projector augmented wave (GIPAW) NMR‐CASTEP DFT approaches, which account for the short‐ and long‐range symmetries, periodicities and interaction‐potential characteristics for all elements (and particularly the heavy elements) in comparison with Gaussian 03 methods, which focus on terminated portions of the total structure.     

Enhanced Anion Binding from Unusual Coordination Modes of Bis(thiourea) Ligands in Platinum Group Metal Complexes

Treatment of a range of bis(thiourea) ligands with inert organometallic transition‐metal ions gives a number of novel complexes that exhibit unusual ligand binding modes and significantly enhanced anion binding ability. The ruthenium(II) complex [Ru(η⁶‐p‐cymene)(κS,S′,N‐ L³ ?H)]⁺ ( 2 b ) possesses juxtaposed four‐ and seven‐membered chelate rings and binds anions as both 1:1 and 2:1 host guest complexes. The pyridyl bis(thiourea) complex [Ru(η⁶‐p‐cymeme)(κS,S′,N_py‐ L⁴ )]²⁺ ( 4 ) binds anions in both 1:1 and 1:2 species, whereas the free ligand is ineffective because of intramolecular NH???N hydrogen bonding. Novel palladium(II) complexes with nine‐ and ten‐membered chelate rings are also reported.     

The stereochemical assignment of acyclic polyols: a computational study of the NMR data of a library of stereopentad sequences from polyketide natural products

The reliable stereochemical assignment of flexible molecules, such as acyclic polypropionates is an enormously challenging task. This is illustrated by the NMR chemical shifts for a complete set of sixteen diastereomeric stereopentads whose experimental data is reported here for the first time. Although the experimental spectra are very similar to each other, analysis of the similarity between the shifts of different diastereoisomers reveals that some diastereoisomers are much more distinctive than others. In addition, the NMR shifts of the sixteen compounds have also been calculated using DFT GIAO calculations, and the use of our recently developed CP3 parameter for structure assignment is illustrated for these molecules. Even in cases where the experimental spectra are very similar, our CP3 parameter makes possible the correct assignment of pairs of diastereoisomers with high confidence.     

Synthesis and bioactivity of (±)-tetrahydrohaliclonacyclamine A

The total synthesis of tetrahydrohaliclonacyclamine A (5) is described. A key step involves the hydrogenation of an unsaturated bis-piperidine incorporated into a 17-membered macrocycle to provide the cis-syn-cis stereochemistry common to haliclonacyclamines A-D. The hydrogenation product is advanced to the title compound following a five-step reaction sequence. Tetrahydrohaliclonacyclamine A is shown to bind to a variety of ion channels/GPCRs and act as a muscarinic M₁ antagonist.     

Evaluation of Raman probe for oesophageal cancer diagnostics

Early detection of (pre-)cancerous changes improves prognosis, therefore in the UK patients at high risk of developing gastrointestinal cancers are enrolled on endoscopic surveillance programmes or the Bowel Cancer Screening Programme. The current gold standard technique for the detection of pre-cancerous changes in the gastrointestinal tract is histopathological analysis of biopsy tissue collected at endoscopy. This relies upon subjective assessment of morphological changes within the excised tissue samples and poor targeting of pre-malignant lesions. Raman spectroscopy offers a number of potential advantages for in vivo assessment of tissue at endoscopy. The performance of a custom built Raman probe as a biopsy targeting tool has been evaluated using excised biopsy material. Multivariate classification models have been used to demonstrate the likely ability of a miniature, confocal, fibre optic Raman probe to be used as an optical biopsy tool at endoscopy to provide spectral information in clinically practicable timescales. This technique could facilitate improved targeting of excisional biopsy with associated clinical benefits.     

Novel bismuth and lead coordination polymers synthesized with pyridine-2,5-dicarboxylates: two single component "white" light emitting phosphors

New two-dimensional (2D) bismuth and three-dimensional (3D) lead based coordination polymers containing pyridine-2,5-dicarboxylate ligands (H(2)pydc) have been synthesized hydrothermally and characterized by single crystal X-ray diffraction. Bi(3)(μ(3)-O)(2)(pydc)(2)(Hpydc)(H(2)O)(2) (1), which crystallizes in the space group P1? (a = 8.7256(5) ?, b = 11.1217(7) ?, c = 14.0933(9) ?, α = 85.239(1)°, β = 98.582(1)°, γ = 71.106(1)°), has a 3D structure that contains Bi(6)O(4) clusters that connect into 2D sheets via linking ligands. The sheets form a 3D supramolecular structure via hydrogen bonding along the z-axis. Pb(pydc)(H(2)O) (2), which crystallizes in the space group P2(1)/c (a = 10.8343(14) ?, b = 11.2099(15) ?, c = 6.6573(9) ?, β = 90.697(2)°), contains 1D chains of corner-sharing distorted face capped trigonal prisms that are connected into a 3D framework via the pydc ligand. In addition, the ligands are hydrogen bonded to each other. Both 1 and 2 are single component "white" light emitting phosphors and are shown to exhibit "white" luminescence that covers a much wider spectral range than is observed for the as received H(2)pydc ligand.