Palladium(0)-catalyzed cascade one-pot synthesis of isoxazolidines

A highly diastereoselective cascade reaction protocol has been developed for the synthesis of isoxazolidine derivatives utilizing aryl halides, O-homoallyl hydroxylamine and palladium(0) in a one-pot reaction.     

Effects of traditional processing methods of linseed oil on the composition of its triacylglycerols

Different oil processing methods were performed, which included washing with water and treatment with lead-based driers, with and without heating to different temperatures, giving a set of 7 oils to be investigated. The effects of the traditional processing methods of linseed oil on its triacylglycerol (TAG) composition were studied, using the following analytical methods: high performance size exclusion chromatography (HPSEC), Fourier transform infrared spectroscopy (FTIR), high-performance liquid chromatography-atmospheric pressure chemical ionisation-mass spectrometry (HPLC-APCI-MS), direct temperature resolved mass spectrometry (DTMS), matrix assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF-MS), and electrospray ionisation Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS). A decrease of the initial cis-double bonds and the formation of trans-double bonds upon heating of the oils was observed. Heating a lead and oil mixture to 150 degrees C, or heating the oil alone to 300 degrees C led to the highest degree of oxidation. A difference was observed for the oxidation patterns for oils with and without the addition of lead. Furthermore, levels of oxygen incorporation were higher when lead was added to the oil. High temperature treatment of the oils resulted in an increased average molecular weight. The changes in the initial conformation of the double bond systems observed with FTIR were supported by HPLC-APCI-MS measurements that showed the formation of a number of new isomeric TAGs in the heated oil compared to freshly pressed, untreated oil. Oligomerisation up to hexamers was observed with HPSEC, and MALDI-TOF-MS. The formation of oligomers up to trimers only, however, was observed with ESI-FTICR-MS. Incorporation of oxygen was mainly observed with MALDI-TOF-MS and ESI-FTICR-MS whereas with DTMS and FTIR hardly any evidence was found for this.     

Sacrificial-Template-Assisted Syntheses of Aluminate and Titanate Nanonets via Interfacial Reaction Growth

Crystalline FeAlO₃/FeAl₂O₄ nanonets were synthesized by a modified template-assisted approach using anodic aluminum oxide (AAO) as a reactive and sacrificial template to direct and promote interfacial reaction growth (IRG). The as-prepared nanonets replicate the morphology of the porous AAO template and contain mixed FeAlO₃ and FeAl₂O₄. To extend the applicability of the sacrificial-template-assisted IRG approach, porous anodic titanium oxide (ATO) was used as template in place of AAO, giving rise to Zn₂TiO₄ nanonet/nanotube and PbTiO₃ nanonet/nanotube. These latter products are polycrystalline due to the polycrystalline nature of the ATO template. Growth mechanism for the formation of the Zn₂TiO₄ and PbTiO₃ nanostructures is proposed. The present study shows that the IRG approach can be extended to fabricate patterned complex oxide nanomaterials that may find applications in a wide range of nanotechnologies such as electronics, photonics and spintronics.     

Structural and electrical properties of nickel–iron thin film on copper substrate for dynamic random access memory applications

Using pulse electrodeposition technique, nano crystalline NiFe films were deposited on conductive copper substrates, under galvanostatic mode in an ultrasonic field at different conditions such as pulse current magnitude, deposition time and ultrasonic bath temperature. As-prepared NiFe/Cu thin films were characterized for phase analysis, surface morphology, surface roughness and resistivity measurements. The results show that the use of ultrasonic bath at room temperature has reduced the surface roughness, resistivity, average grain size and crystallite size of NiFe/Cu thin films. The resistivity is reduced with increasing deposition current from 44.2 µΩ cm at 40 mA to 33.0 µΩ cm at 100 mA. On the other hand, a significant drop of the resistivity from 35.7 to 9.4 µΩ cm is observed if the deposition time was reduced from 5 to 3 min.     

Diversification of Glycosyl Compounds via Glycosyl Radicals

Glycosyl radical functionalization is one of the central topics in synthetic carbohydrate chemistry. Recent advances in metal-catalyzed cross-coupling chemistry and metallaphotoredox catalysis provided powerful platforms for glycosyl radical diversification. In particular, the discovery of new glycosyl radical precursors in conjunction with these advanced reaction technologies have significantly expanded the space for glycosyl compound synthesis. In this Review, we highlight the most recent progress in this area starting from 2021, and the reports included will be categorized based on different reaction types for better clarity.     

Stereoselective C-Aryl Glycosylation by Catalytic Cross-Coupling of Heteroaryl Glycosyl Sulfones

Stereoselective C-glycosylation reactions are increasingly gaining attention in carbohydrate chemistry because they enable glycosyl precursors, readily accessible as anomeric mixtures, to converge to a single diastereomeric product. However, controlling the stereochemical outcome through transition-metal catalysis remains challenging, and methods that leverage bench-stable heteroaryl glycosyl sulfone donors to facilitate glycosylation are rare. Herein, we show two complementary nonprecious metal catalytic systems, based on iron or nickel, which are capable of promoting efficient C−C coupling between heteroaryl glycosyl sulfones and aromatic nucleophiles or electrophiles through distinct mechanisms and modes of activation. Diverse C-aryl glycosides were secured with excellent selectivity, scope, and functional-group compatibility, and reliable access to both α and β isomers was possible for key sugar residues.     

Surface Water as an Initial Proton Source for the Electrochemical CO Reduction Reaction on Copper Surfaces

We have employed in situ electrochemical shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) and density functional theory (DFT) calculations to study the CO reduction reaction (CORR) on Cu single-crystal surfaces under various conditions. Coadsorbed and structure-/potential-dependent surface species, including *CO, Cu−O_ad, and Cu−OH_ad, were identified using electrochemical spectroscopy and isotope labeling. The relative abundance of *OH follows a “volcano” trend with applied potentials in aqueous solutions, which is yet absent in absolute alcoholic solutions. Combined with DFT calculations, we propose that the surface H₂O can serve as a strong proton donor for the first protonation step in both the C₁ and C₂ pathways of CORR at various applied potentials in alkaline electrolytes, leaving adsorbed *OH on the surface. This work provides fresh insights into the initial protonation steps and identity of key interfacial intermediates formed during CORR on Cu surfaces.     

Environmental research for art conservation (ERA)

The basic concept of this project is to identify and then use the changes which occur in the chemical and physical properties of traditional paint media both to indicate and integrate the effects of environmental conditions on paintings. To achieve this aim, test paint films are being prepared in accordance with traditional artists' recipes. Changes in material properties are monitored using a combination of non-invasive spectroscopy (Bacci), microsensors, thermoanalytical techniques (Odlyha), and microscale analytical mass spectrometry for molecular structure analysis (Boon). The test strips are calibrated by exposure to controlled environments (light, temperature, relative humidity and noxious gases) and alterations in their properties are quantified. This provides information on the nature and rate of change at the molecular level and a data base for evaluating the molecular monitoring strips after their exposure in the field. Field sites have been selected and include various locations in the Tate Gallery (UK), Sandham Chapel (Burghclere, UK), the Uffizi Gallery (It) and the Rijksmuseum (NL). Environmental conditions of some of these locations are being evaluated at present using the glass sensors described in project EV5VCT92 0144. Small piezoelectric quartz crystal humidity sensors will be installed to determine localised variations in relative humidity and temperature on [1] Stanley Spencer paintings in Sandham Chapel and [2] Giotto's Madonna di Ognissanti in the Uffizi Gallery. In addition novel coatings using picture varnishes are being applied to similar piezoelectric quartz crystal sensors to evaluate the effects of environmental impact on the chemistry of varnishes on paintings. Data are also being collected on the nature of chemical and physical changes in varnishes and paint media in actual paintings at the molecular level.Paper presented at the European Commission Workshop in Würzburg (December, 1995) on the project EV5VCT94 0548.     

Ultrafiltration and Pyrolysis Gas Chromatography Mass Spectrometry of Chlorolignins in Pulp Mill Effluent

Abstract

Investigations on the effluent of a German pulp mill on the river Rhine using ultrafiltration and pyrolysis gas chromatography mass spectrometry have shown the presence of several chlorinated 2-methoxyphenols, which probably originate from chlorinated lignin or lignosulfic acid. Chlorinated phenolic pyrolysis products identified were 2-methoxy-6-chlorophenol, 2-methoxy-4-methyl-6-chlorophenol, 2-methoxy-dichlorophenol, 2-methoxy-4-vinyl-6-chlorophenol, 2-methoxy-4-(chloropropyl)phenol, 2-methoxy-4-(prop-2-enyl)-6-chlorophenol, 2-methoxy-4-(propan-2-one)-6-chlorophenol, 2-methoxy-3, 5, 6-trichlorophenol, 2-methoxy-4-vinyl-3, 5, 6-trichlorophenol. Monochlorinated 2-methoxyphenols were the dominant chlorinated pyrolysis products, smaller amounts of di- and trichloromethoxyphenols were also detected. 2-Methoxyphenols (guaiacols) were the dominant lignin pyrolysis products, only small amounts of 2, 6-dimethoxyphenols (syringols) were detected. This indicates the origin from soft wood. A Py-(GC)-(MS)-TIC-chromatogram of reference spruce milled wood lignin is comparable with the TIC-chromatogram of pulp mill effluent MW-fraction > 10,000, showing many similar compounds. The ultrafiltration fraction 1000 < MW < 10,000 showed a remarkably empty TIC-chromatogram, with 2-methoxyphenol and 2-methoxy-6-chlorophenol as the only significant phenolic peaks. This may indicate a high degree of oxidation/chlorination of lignin in this fraction.