Periodic solutions of difference Runge-Kutta schemes

Translated from Matematicheskie Zametki, Vol. 49, No. 6, pp. 92–97, June, 1991.     

Anodic oxidation of olefins in presence of fluorine anion

Russian Chemical Bulletin -     

Luminescent Zn and Pd tetranaphthaloporphyrins

Zn and Pd complexes of meso-tetraphenyltetranaphthaloporphyrins (Ph(4)TNP) exhibit strong infrared absorption bands and luminesce in solutions at room temperature. S1 --> S0 fluorescence (lambda(max) = 732 nm, phi = 5.3%) is the predominant emission in the case of ZnPh(4)TNP (1). This emission is in part due to the delayed fluorescence (phi = 1.1%). Phosphorescence (T1 --> S0) of 1 (lambda(max) = 973 nm) is very weak (phi = 0.04%) and occurs with lifetime of about 440 micros in deoxygenated DMF. In the case of PdPh(4)TNP (2), almost no S1 --> S0 fluorescence could be observed, while the main emission detected was T1 --> S0 phosphorescence (lambda(max) = 938 nm). The phosphorescence of 2 occurs with lifetime of about 65 micros and (phi=6.5%) in deoxygenated DMF solution. Metalloporphyrins 1 and 2 are promising near infrared dyes biomedical applications.     

Reductive coupling of fluorolefines

Perfluorolefines at cathodic reduction or with one- electron donor reagent (C₁₀H₈Na) in aprotic solvents undergo to the defluorination with formation of new double bonds. Such defluorination in the case of perfluoro-2-methylpentene- 2 (I) is accompanied by the dimerization and cyclization producing cyclo-butene C₁₂F₂₂ (II) and diene C_l2F₂₀ (III) in 40 to 70% yields. The proposed reaction scheme includes the next steps: (a) - the successive two- electron transfer on olefine with elimination of F^? and formation of the anion (IV); (b) - the nucleophilic attack of the double bond by IV and the following cyclization giving olefine (V);

(c) - the isomerization of V into the more stable butene II and/of (d) - the furthur reduction and defluorination of V.

The nucleophilic isomerization of V is a main process at electrolysis of I in the presence of fluoride ion at low current density (II:III = 10:1). The furthur defluorination becomes preferable pathway when electrolysis of I is carried out at high current density and with Et₄NBF₄ as a supporting electrolyte (II:III = 1:9).I undergoes similar defluorination and coupling reactions with some three-valent phosphorus compounds.

However, the structure of VI occurs to be different from II and so the coupling reaction via nucleophilic addition (e) leads to another products as compared with the electron-transfer reactions.     

Synthesis of N,N′-bis[4-(1H-1,2,3-triazol-1-yl)furazan-3-yl]-methylenediamine derivatives

[3+2] Cycloaddition of azide groups of N,N′-bis(4-azidofurazan-3-yl)methylenediamine to 1,3-dicarbonyl compounds and malonodinitrile was shown to proceed regioselectively with the formation of the corresponding N,N′-bis[4-(1H-1,2,3-triazol-1-yl)furazan-3-yl]methylenediamine derivatives. The reactions of N,N′-bis(4-azidofurazan-3-yl)methylenediamine with cyanoacetic acid ethyl ester and amide led to the formation of the product of transformation of the azide group in the starting compound to the amino groups.     

Static and switching characteristics of field-controlled integrated thyristor

The static parameters of and switching transients in an advanced high-voltage high-speed switching device—a MOSFET-controlled integrated thyristor—and their dependences on the geometry and electrophysical properties of base layers in the n ⁺ pnn’p ⁺ device structure are studied experimentally. It is shown that the residual resistance of the high-voltage (∼2.5 kV) microthyristor chip in the on-state is much smaller than that of the high-voltage IGBT with the speed of the former kept at a sufficiently high level. The new device is multifunctional and can operate under different operating conditions. Specifically, it can be turned off by shunting the n ⁺ p emitter by an add-on MOSFET, by applying a gate current pulse, and in the cascode turn-off regime. In these regimes, the ultimate value of the turn-off current noticeably grows.     

Synthesis of dihydrofurocoumarins via palladium-catalyzed annulation of 1,3-dienes by o-iodoacetoxycoumarins

[reaction: see text] A variety of biologically interesting dihydrofurocoumarins have been synthesized in high yields by the palladium-catalyzed annulation of 1,3-dienes by o-iodoacetoxycoumarins. This reaction is very general and regioselective, and a wide variety of terminal, cyclic, and internal 1,3-dienes can be utilized.