Syntheses based on dimethylpyrazoles. 9. Synthesis and spectral peculiarities of isomeric pyrazolo[3′,4′-5,6]- and-[5′,4′-5,6]-pyrimido[1,2-b]benzo[d,e]isoquinoline-4,12-diones

2-Methyl-2,4,12,13H-pyrazolo[3,4-5,6]pyrimido[1,2-b]benzo[d,e]isoquinoline-4,12-dione and its 8-nitro- and 8-amino-substituted derivatives were obtained starting from 4-amino-3-carbamoyl-1-methylpyrazole and naphthalic and 4-nitronaphthalic anhydrides. The spectral properties of the synthesized compounds were studied.See [1] for Communication 8.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 237–241, February, 1990.     

Effect of a Nickel Bipyridyl Complex on the Reduction of Organic Halides

Indirect reduction of 1-phenylethylbromide (I) and 1-(4-isobutylphenyl)ethylchloride (II) in a carbon dioxide atmosphere containing tris(2,2-bipyridyl)nickel tetrafluoroborate (BPN) is studied. In the reactions the BPN complex exhibits properties of a one-electron mediator and catalyzes radical generation from aryl halides, which mostly undergo dimerization. Electroreduction of I and II in the presence of -cyclodextrin and BPN yields biaryls with a low enanthioselectivity (1.5%), which may indicate generation of a small amount of inclusion complexes and dimerization of intermediate radicals in the hydrophobic cavity of -cyclodextrin.     

Specifics of Interaction of Acetone Molecules with Quasi-free Electrons: Analysis of Positron Annihilation Characteristics in Aqueous and Alcoholic Acetone Solutions

The yields of formation of radiolytic hydrogen (H₂) and orthopositronium (o-Ps) in aqueous and alcoholic acetone solutions were experimentally determined. A decrease in the o-Ps yield with an increase in the acetone concentration is much weaker than the decline in the yield of solvated electrons (e^– _s) under picosecond pulse radiolysis conditions. In contrast, the decrease in the o-Ps yield is minimal in higher alcohols where the inhibiting action of acetone e^– _s is most pronounced. These findings seem to contradict the conventional concepts of Ps formation via the intratrack reaction of positron recombination with a track electron (e^–), which competes with the reaction of e^– scavenging by dissolved acetone molecules. This contradiction can be eliminated, assuming that the scavenging of e^– by acetone begins from the formation of the weakly bound transient state (CH₃)₂CO···e^– capable of donating e^– to a positron. This opens up an additional pathway for the formation of the Ps atom.     

Fluorenyl-containing sulfonated poly(aryl ether ether ketone ketone)s (SPFEEKK) for fuel cell applications

A series of fluorenyl-containing sulfonated poly(aryl ether ether ketone ketone)s (SPFEEKK) were synthesized via aromatic nucleophilic substitution polymerization. The sulfonation content (SC) was controlled by the feed ratios of sulfonated and nonsulfonated monomers. Flexible and strong membranes in the sulfonic acid form were obtained from cast membranes in the sodium salt forms by treatment with acid. The thermal properties, water uptake, swelling ratio, water state, oxidative stability, proton conductivity and methanol permeability were investigated. All the polymers had proton conductivities greater than 1 × 10⁻² S/cm at room temperature, and the conductivity values of m-SPFEEKK-80 and p-SPFEEKK-80 were up to 1.86 × 10⁻¹ and 1.78 × 10⁻¹ S/cm at 100 °C. This series of polymers also possessed good dimensional stability in water and low methanol crossover.     

Photon echoes in single- and trilayer semiconductor films of different nanosized thicknesses and their properties

A femtosecond stimulated photon echo is detected for the first time in thin semiconductor films with thicknesses of 100, 800, and 2400 nm. It is established that relaxation time T ₁ varies with ZnO film thickness, taking values of 0.96, 2.96, and 4.312 ps at thicknesses of 2400, 800, and 100 nm, respectively. For ZnO/Si⁺/Si^? trilayer films, the relaxation time is T ₁ = 12.73 ps.     

Anodic trifluoromethylation of 10-undecylenic acid

The electrooxidation of a (～3: 1) mixture of trifluoroacetic and 10-undecylenic acids in MeCN with an aqueous KOH addition on different anodic catalysts was studied. The oxidation of trifluoroacetate ions that forms trifluoromethyl radicals is the key stage of the process, while 10-undecylenic acid seems to be merely an acceptor of the electrogenerated radicals, i.e., shows the chemical properties characteristic of olefins. The galvanostatic electrolysis of trifluoroacetic and 10-undecylenic acids led to a mixture of the products of trifluoromethylation of the latter and the products of coupling of the formed radical species. According to a qualitative estimation, the total yield of these products was 74%.     

Synthesis of layered metal dichalcogenides with organic cations by electrochemical reduction in suspensions

Intercalated group IVB-VIB metal disulfides and diselenides MX₂ (M = Ti, Zr, Nb, Mo) can be obtained by electrochemical reduction of the corresponding MX₂ in the presence of tetraalkylammonium salt. An original approach was used, which allowed effective reduction of these insoluble substances in the form of powders suspended in an organic solvent using the standard electrolysis technique in solutions in a one-space electrolyzer with a soluble anode. Using electron transfer mediators in the process afforded intercalated compounds with yields of 60–100%.     

Mild Approach to the Deprotection of Troc from Protected Amines Using Mischmetal and TMSCl

The 2,2,2-trichloroethoxycarbonyl (Troc) protecting group was efficiently removed from Troc-protected aliphatic and aromatic amines and also some Troc, Tos- and Troc, Ac-protected amines using activated mischmetal (MM). All reactions were performed by refluxing in dry tetrahydrofuran under an argon atmosphere and gave moderate to excellent yields. Several new compounds were synthesized, and new data about reactivity of Troc group were obtained.     

Asymptotically optimal pointwise and minimax quickest change-point detection for dependent data

We consider the quickest change-point detection problem in pointwise and minimax settings for general dependent data models. Two new classes of sequential detection procedures associated with the maximal “local” probability of a false alarm within a period of some fixed length are introduced. For these classes of detection procedures, we consider two popular risks: the expected positive part of the delay to detection and the conditional delay to detection. Under very general conditions for the observations, we show that the popular Shiryaev–Roberts procedure is asymptotically optimal, as the local probability of false alarm goes to zero, with respect to both these risks pointwise (uniformly for every possible point of change) and in the minimax sense (with respect to maximal over point of change expected detection delays). The conditions are formulated in terms of the rate of convergence in the strong law of large numbers for the log-likelihood ratios between the “change” and “no-change” hypotheses, specifically as a uniform complete convergence of the normalized log-likelihood ratio to a positive and finite number. We also develop tools and a set of sufficient conditions for verification of the uniform complete convergence for a large class of Markov processes. These tools are based on concentration inequalities for functions of Markov processes and the Meyn–Tweedie geometric ergodic theory. Finally, we check these sufficient conditions for a number of challenging examples (time series) frequently arising in applications, such as autoregression, autoregressive GARCH, etc.