Diels-Alder reaction using a dendritic copper(II) triflate-catalyst: a positive dendritic effect on the chemical yield

A series of dendritic ligands with a 2,2′-bipyridine core was synthesized through the coupling of 4,4′-dihydroxy-2,2′-bipyridine with poly(arylether) dendron in fair yields. The corresponding copper(II) trifluoromethanesulfonate (triflate) dendrimers were applied as a Lewis acid catalyst to the Diels-Alder reaction. A positive dendritic effect on the chemical yields of adducts was observed.     

Epoxy polymer coating to prevent the corrosion of aluminum nanoparticles

Aluminum nanoparticles were coated by epoxy polymer in order to prevent the corrosion reaction. The coverage of the epoxy polymer film was controlled from 0% to 100%, which changed the corrosion rate of nanoparticles quantitatively. The surface of the polymer coating was investigated by transmission electron microscopy (TEM) and atomic force microscopy (AFM), and the corrosion resistance of these nanoparticles was estimated by the wet/dry corrosion test on platinum (Pt) plate with a NaCl solution. From a TEM analysis, 10 mass% polymer‐coated Al particles in the synthesis were almost 100% covered on the surface by a polymer film of 10 nm thick. On the other hand, 3 mass% polymer‐coated Al was partially covered by a film. In the AFM–Kelvin force microscopy, the potential around the Al particles had a relatively low value by the polymer coating, which indicated that the conductivity of the Al was isolated from Pt plate by the polymer. Both the corrosion and H₂ evolution reaction rates were quantitatively reduced by the mass% of polymer coating. In the case of 10 mass% coated sample, there was very little corrosion of Al nanoparticles. This fact suggested that the electrochemical reaction was suppressed by the polymer coating. Thus, it was found that the corrosion reaction rate of Al nanoparticles could be quantitatively suppressed by the mass% of epoxy coating. Copyright © 2015 John Wiley & Sons, Ltd.     

Comparative studies of spectrochemical characteristics between axial and radial observations in inductively coupled plasma optical emission spectrometry.

By using an ICP optical emission spectrometer having two different observation modes, the authors compared the spectrochemical characteristics of various emission lines as viewed from the axial direction and the direction radial to the long axis of the plasma. The excitation temperature, the emission intensity, and the degree of ionization were investigated when iron and chromium were employed as the test sample and further potassium was added as an interfering element. These observations could lead to a similar conclusion that the emission intensities from the axial direction were more easily affected by the potassium addition. The reason for this effect is probably because the portion of the plasma observed from the axial direction includes the tail zone which is apart from the induction zone and thus has lower temperatures. On the other hand, in the radial observation, one can observe the emission intensities from a narrow portion of the plasma just above the load coil. The axial observation mode gave better analytical performance, including a lower detection limit as well as a better signal-to-background ratio, compared to the radial observation mode. However, interferences from co-existing elements should be noted if the axial observation is employed in practical applications.     

Ligand‐Controlled Synthesis of [3]‐ and [4]Cyclo‐9,9‐dimethyl‐2,7‐fluorenes through Triangle‐ and Square‐Shaped Platinum Intermediates

The syntheses of [3]‐ and [4]cyclo‐9,9‐dimethyl‐2,7‐fluorenes ([3] and [4]CFRs), cyclic trimer, and tetramers of 9,9‐dimethyl‐2,7‐fluorene (FR), respectively, were achieved by the platinum‐mediated assembly of FR units and subsequent reductive elimination of platinum. A triangle‐shaped tris‐platinum complex and a square‐shaped tetra‐platinum complex were obtained by changing the platinum ligand. The structure of the triangle complex was unambiguously determined by X‐ray crystallographic analysis. Reductive elimination of each complex gave [3] and [4]CFRs. Two rotamers of [3]CFR were sufficiently stable at room temperature and were separated by chromatography. The physical properties of the CFRs were also investigated theoretically and experimentally.     

Synthesis of ketimines via palladium complex-catalyzed cross-coupling of imidoyl chlorides with organotin compounds

Imidoyl chlorides were successfully transformed into ketimines when treated with organotin compounds in the presence of palladium complex catalysts.     

Dehydrogenative condensation of monohydrosilanes yielding disilanes in the presence of platinum complex catalysts

Dimethylphenylsilane was catalytically dehydrogenated and condensed in the presence of platinum complexes to give 1,1,2,2-tetramethyl-1,2-diphenyl-disilane.     

Dilatometric studies of reaction volumes for the formation of metal complexes in several solvents

A convenient technique is described to determine reaction volumes by means of direct dilatometry. Reaction volumes were determined for the following complexation reactions: formation of monoamminenickel(II) in water (–0.1±0.5 cm³-mol^–1); formation of the 1:1 nickel(II) complex with isoquinoline in methanol and ethanol (3.2±0.1 and 1.1±0.1 cm³-mol^–1, respectively); formation of the 1:1 isothiocyanatoiron(III) complex in water, Me₂SO, and DMF (8.9±0.2, 12.4±0.7, and 25.1±0.3 cm³-mol^–1, respectively); formation of the 18-crown-6 potassium complex in water (10.9±0.2 cm³-mol^–1). We discussed these values in terms of electrostriction and molecular size.     

Stability of phosphines under hydroformylation conditions

Phosphorus-carbon bonds of p-substituted triphenylphosphines were found to be cleaved under hydroformylation conditions in the presence of a rhodium, ruthenium, or cobalt carbonyl. Only p-isomers of the decomposition products (substituted benzaldehyde, benzyl alcohol, and/or biphenyl) were formed. The ability of metal carbonyls to cleave the PC bonds was Rh > Co > Ru. Tributylphosphine was stable under the conditions. The stability of metal carbonyl-phosphine catalyst systems was also examined and compared with the extent of PC bond cleavage.     

Multi-step application of immobilized reagents and scavengers: a total synthesis of epothilone C

The total synthesis of the cytotoxic antitumour natural product epothilone C has provided a stage for the exploitation and further development of immobilized reagent methods. A stereoselective convergent synthetic strategy was applied, incorporating polymer-supported reagents, catalysts, scavengers and catch-and-release techniques to avoid frequent aqueous work-up and chromatographic purification.