Asymmetric Allylic Substitution Reactions with a Xylophos-Pd Catalyst

Summary.  The chiral diphosphine ligand xylophos (1) was tested as an auxiliary in palladium catalyzed allylic substitution reactions. Whereas its activity was found to be generally good only in the case of 1,3-diphenylprop-2-en-1-yl acetate, a fair level of asymmetric induction was achieved with sodium dimethyl malonate (83%ee) and benzylamine (66%ee) as nucleophiles. Received June 13, 2000. Accepted July 3, 2000     

1‐Chloro‐1,1‐di­fluoro‐N‐(4‐methoxy­phenyl)‐3‐(pyrrolidin‐2‐yl­idene)­propan‐2‐imine

In the title compound, C₁₄H₁₅ClF₂N₂O, the Z configuration has been confirmed. The molecular structure shows an intramolecular N—H?N hydrogen bond [H?N 2.04 (6), N?N 2.709 (6) Å and N—H?N 124 (5)°]. This interaction could be responsible for the Z configuration.     

The Reaction of Sulfur Dioxide Radical Cation with Hydrogen and its Relevance in Solar Geoengineering Models

SO₂ has been proposed in solar geoengineering as a precursor of H₂SO₄ aerosol, a cooling agent active in the stratosphere to contrast climate change. Atmospheric ionization sources can ionize SO₂ into excited states of , which quickly reacts with trace gases in the stratosphere. In this work we explore the reaction of with excited by tunable synchrotron radiation, leading to ( ), where H contributes to O₃ depletion and OH formation. Density Functional Theory and Variational Transition State Theory have been used to investigate the dynamics of the title barrierless and exothermic reaction. The present results suggest that solar geoengineering models should test the reactivity of with major trace gases in the stratosphere, such as H₂ since this is a relevant channel for the OH formation during the nighttime when there is not OH production by sunlight. OH oxides SO₂, triggering the chemical reactions leading to H₂SO₄ aerosol.     

Experimental and Numerical Study of Polypropylene/Polyethylene Thin Foil in Biaxial Tension

The material under consideration is a thermoplastic copolymer blend of polypropylene and polyethylene (PP/PE), constituting the core layer of a steel/polymer/steel composite material. A biaxial loading machine was developed for studying the behavior of the copolymer subjected to in-plane complex stress states. A study on the shape of the specimen by means of numerical finite element simulations and preliminary experimental tests are carried out, in order to obtain a maximization of the strain distribution in the middle region of the cruciform specimen. Afterwards, the sensitivity of the mechanical response under both equibiaxial and non-equibiaxial conditions is addressed. All the experiments are monitored by means of a digital image correlation (DIC) system, providing full-field measurements of the displacements, and, consequently, of the strain distribution. The presented experimental results will be used for validating the material model developed for the PP/PE layer material. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Carbon capture and storage and transboundary pollution: A differential game approach

We study the strategic behavior of two countries facing transboundary CO₂ pollution under a differential game setting. In our model, the reduction of CO₂ concentration occurs through the carbon capture and storage process, rather than through the adoption of cleaner technologies. Furthermore, we first provide the explicit short-run dynamics for this dynamic game with symmetric open-loop and a special Markovian Nash strategy. Then, we compare these strategies at the games’ steady states and along some balanced growth paths. Our results show that if the initial level of CO₂ is relatively high, state dependent emissions reductions can lead to higher overall environmental quality, hence, feedback strategy leads to less social waste.     

First direct fluorescence polarization assay for the detection and quantification of spirolides in mussel samples

In 2009, we achieve the first inhibition FP assay to detect imine cyclic toxins. In the present paper we propose a new FP assay for direct quantify spirolides. This new method has resulted in significant improvement of sensitivity, rapidity and accessibility. In the method design, nicotinic acetylcholine receptor from Torpedo marmorata membranes labelled with a derivative of fluorescein was used. Spirolides, 13-desmethyl spirolide C (13-desMeC) and 13,19-didesmethyl spirolide C (13,19-didesMeC) were extracted and purified from cultures of the Alexandrium ostenfeldii dinoflagellate. Data showed the decrease of FP when toxin concentration was increased. Thus, a relationship between the FP units and the spirolides amount present in a sample was obtained. This direct assay is a reproducible, simple and very sensitive method with a detection limit about 25 nM for 13-desMeC and 150 nM for 13,19-didesMeC. The procedure was used to measure spirolides in mussel samples using an extraction and clean up protocol suitable for the FP assay. Results obtained show that this method is able to quantify 13-desMeC in the range of 50–350 μg kg⁻¹ meat. Other liposoluble toxins did not interfere with the assay, proving a specific method. Moreover, the matrix do not affect in the range of toxin concentrations that involving risk of spirolides intoxication.     

Studies on the synthesis of a hindered analogue of the antitumour agent CC-1065

Studies on the synthesis of a sterically congested analogue of CC-1065 (2) are described. Interesting steric effects in the reactivity of intermediates and the rare predominance of keto tautomers in some phenols were observed.     

Ionic liquid–water mixtures as solvents for poly(N-vinylimidazole)

Ionic liquids extend the Hofmeister series and create a wide range of new possibilities for processes involving salt effects on both soluble and crosslinked systems. This work reports on some mixtures of water with NaCl or an ionic liquid, either 1-ethyl-3-methylimidazolium tosylate or 1-hexyl-3-methylimidazolium chloride, which are better solvents for linear poly(N-vinylimidazole) (L-PVI) than water, i.e., that exhibit a salting-in effect. The intensity of the salt effects was measured on the basis of the polymer solubility, the decrease in polymer–solvent interaction parameter (measured by light scattering), and the increase of coil size (measured through the intrinsic viscosity). It was thus found that the intensity of the salting-in effect of either NaCl or 1-hexyl-3-methylimidazolium chloride on L-PVI is different (larger for the ionic liquid), which denotes that salt effects are not under anion control, and the mechanisms operating in the linear and crosslinked polymers are different. These results are discussed after accounting for the role of ion–polymer interactions.     

Engineering the Biosynthesis of the Polyketide-Nonribosomal Peptide Collismycin A for Generation of Analogs with Neuroprotective Activity

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