Double amination of 2-fluoroallylic acetates by palladium catalysts

We accomplished the palladium-catalyzed double substitution of 2-haloallylic acetates with nitrogen nucleophiles. During the Pd₂(dba)₃/DPPE-catalyzed reaction of 2-fluoroallylic acetates with N-substituted-p-toluenesulfonamide, two equivalents of nitrogen nucleophiles were introduced to the allyl unit with a Z-selectivity through the carbon–fluorine bond cleavage. We further demonstrated the reaction of 2-chloroallylic acetates, and succeeded in obtaining the same doubly-substituted products in good yields with a high Z-selectivity.     

Reaction of salts of nitroaminotetrazoles with alkyl iodides

The reaction of salts of 5-nitroaminotetrazole, 1- and 2-methyl-5-nitroaminotetrazole, and 2-ethyl-5-nitroaminotetrazole with alkyl iodides is studied. It is established that salts of 2-methyl- and 2-ethyl-5-nitroaminotetrazole are alkylated at the nitroamine group while salts of 1-methyl-5-nitroaminotetrazole are alkylated at the second nitrogen atom of the tetrazole fragment with the subsequent splitting off of the methyl group at the 1-position of the tetrazole ring and further alkylation of the nitroamine group. It is shown that salts of 5-nitroaminotetrazole are initally alkylated at the second nitrogen atom of the tetrazole fragment and then at the nitroamine group. It is hypothesized that the initial alkylation of salts of 1-methyl-5-nitroaminotetrazole and 5-nitroaminotetrazole at the second nitrogen atom of the tetrazole fragment results from their nitroimino tautomeric form.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1090–1093, August, 1986.     

Effect of Heavy Atoms on the Doublet Components of the Phosphorescence Spectrum of Triphenylene in Carbon Tetrachloride

Optics and Spectroscopy - Intensity distribution and kinetics of the doublet components of the phosphorescence spectrum of triphenylene in a frozen solution of carbon tetrachloride are analyzed. It...     

Electrical properties, structure, and surface morphology of poly(p-xylylene)–silver nanocomposites synthesized by low-temperature vapor deposition polymerization

The crystalline structure, surface morphology, electrical, and optical properties of thin films of nanocomposites consisting of silver nanoparticles embedded in poly(p-xylylene) matrix prepared by low-temperature vapor deposition polymerization were studied. Depending on the filler content, the average size of silver nanoparticles varied from 2 to 5 nm for nanocomposites with 2 and 12 vol.% of silver, correspondingly. The optical adsorption in the visible region due to surface plasmon resonance also exhibited a clear correlation from silver content, revealing a red shift of the adsorption peak with the increase of the metal concentration. The temperature dependences of the dc resistance of pure p-xylylene condensate and p-xylylene–silver cocondensates during polymerization as well as temperature dependences of the formed poly(p-xylylene)–silver nanocomposites were examined. The observed variation of the temperature dependences of electrical resistance as a function of silver concentration are attributed to different conduction mechanisms and correlated with the structure of the composites. The wide-angle X-ray scattering and AFM measurements consistently show a strong effect of silver content on the nanocomposite structure. The evolution of the size of silver nanoparticles by thermal annealing was demonstrated.     

Ruthenium-catalyzed regioselective [2 + 2 + 2] cyclotrimerization of trifluoromethyl group substituted internal alkynes

It found that the Ru(3)(CO)(12) coordinated with 2-(diphenylphosphino)benzonitrile (2-DPPBN) to effectively catalyze the [2 + 2 + 2] cyclotrimerization of the trifluoromethyl group substituted internal alkynes in high yields with up to >98% regioselectivity. Isolation of a ruthenacyclopentadiene was successful and confirmed that the complex is a reaction intermediate.     

Flow of a single magnetic vortex in a submicron-size superconducting Al disk controlled by radio-frequency currents

We report the first observation of a single-vortex flow in a mesoscopic superconductor. A flow of a single vortex is successfully controlled by an rf current superimposed on a dc current, evidence of which is provided by voltage steps in current-voltage (I-V) characteristics. Irrespective of the number of vortices confined to the disk, we unambiguously observe that when a single vortex inside the disk is driven out of the disk, another vortex enters the disk similarly to two balls colliding in billiards: only one vortex passes through the Al disk at the same time in mesoscopic systems.     

Retention of regiochemistry and chirality in the ruthenium catalyzed allylic alkylation of disubstituted allylic esters

The regiospecific nucleophilic substitution during the ruthenium catalyzed allylic alkylation of 1,3-unsymmetrical disubstituted allylic esters was demonstrated. The nucleophile was selectively introduced at the position originally substituted with leaving group in the 2-DPPBA or ip-pybox ligated [RuCl(2)(p-cymene)](2) catalyzed allylic alkylation of 1,3-unsymmetrical disubstituted allylic esters. The chirality of the optically active allylic esters was also transferred to the alkylated products.     

Microstructural and metal-support interactions of the Pt-CeO2/C catalysts for direct methanol fuel cell application

To understand the ceria promotion effect of Pt-CeO(2)/C catalysts on methanol oxidation, microstructural and metal-oxide interactions of Pt-CeO(2)/C catalysts with an atomic ratio of Pt/Ce between 0.14 and 1.4 were systematically examined using high-resolution transmission electron microscopy and electron energy loss spectroscopy (EELS). With an increasing Pt content in the catalysts, Pt particles gradually invaded into the ceria supports and decoration on Pt particles was observed. Simultaneously, the morphology of the supports was dramatically modified with nanocrystalline and amorphous ceria formed between and/or around the Pt particles. It reveals that the Pt-ceria interaction could take place in the catalysts and the influence of the interaction was enhanced with an increasing Pt/Ce ratio. The EELS study demonstrated that the strong Pt-ceria interaction was related to the redox reaction between Pt and ceria. Experimental results also suggested that the strong interaction between Pt and ceria could contribute to the promotion effect of ceria on the oxidation of methanol.     

In situ 18F-γ-ray-induced Ag nanoparticle formation in the presence of SiO2 nanoparticles under air

The in situ ¹⁸F-γ-ray irradiation of SiO₂ nanoparticles in an aqueous solution containing Ag⁺ led to the reduction of Ag⁺ to Ag⁰ aggregates or Ag⁰ nanoparticles in a small volume (0.1 ml) under air. ¹⁸F was used in the form of ¹⁸F-fluorodeoxyglucose, produced by a cyclotron at our University hospital. The in situ average absorbed dose at the distance of 1 µm in the solution volume (0.1 ml) was calculated to be 12.2 kGy equivalent to a point source of 20 MBq. The SiO₂ nanoparticles had two effects; they enhanced the reduction of Ag⁺ to Ag⁰ aggregates and they acted as reaction sites to prevent aggregation. When Ag⁺ adsorbed on the surface of the SiO₂ nanoparticles, Ag nanoparticles were formed by ¹⁸F γ-rays. The absorption spectra of Ag nanoparticles and Ag⁰ aggregates were markedly different.