N-alkylation of 4-chloro-5-cyano-1,2,3-triazole with orthoformic acid derivatives

The N-alkylation of 4-chloro-5-cyano-1,2,3-triazole with methyl and ethyl orthoformate, and the dimethyl, diethyl and ethylene acetals of DMF has been examined. Methylation gives all three N-methyl isomers, whereas ethylation and hydroxyethylation gives the 2-N-alkyl derivatives only. It has been shown for the first time that it is possible to use DMF ethylene acetal to obtain N-hydroxyethylazoles. The structures of the products were established by¹³C NMR spectroscopy.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 920–924, July, 1988.     

Crytal and molecular structure of hydrido(trichlorostannyl)bis-cyclopentadienyl molybdenum(η5-C5H5)2Mo(H)SnCl3

On the basis of X-ray analysis the crystal and molecular structures of (η₅-C₅H₅)₂Mo(H)SnCl₃ have been determined. The compound crystallizes in the monoclinic system with parameters: a = 8.313(3), b = 13.109(4), c = 6.384(2) Å, β = 106.52(2)°, space group P2₁/m, R = 0.028. The conformation occurring in Cp₂Mo(H)SnCl₃ is that with the maximum repulsion between the chloride atoms and the cyclopentadienyl rings. The hydride H atom is shielded by the cyclopentadienyl groups and chlorine atoms, which accounts for the compound's stability to oxygen and hydrolysis.     

Reduction of copper (II) chloride by molybdenum and rhenium biscyclopentadienyl hydrides. Investigation of the crystal and molecular structure of [(η5-C5H5)2Re]+[CuCl2]−

The reduction of copper (II) chloride by molybdenum and rhenium biscyclopentadienyl hydrides upon their interaction in donor-type solvents has been studied by NMR, X-ray diffraction, and magnetic methods. It is established that the ionic complex [(η⁵-C₅H₅)₂Re]⁺[CuCl₂]^? forms ortho rhombic crystals with a - 13.696(2) Å, b = 7.317(1) Å, c = 5.969(1) Å, space group Pm2₁n, Z = 2. The cyclopentadienyl rings make a bent-sandwich with an angle between the ring centres and Re atom of 150.1°; the ClCuCl angle being 174.8° and the ReCu minimum distance 4.346(29) Å. The solution of [(η⁵-C⁵H₅)²Re]⁺ [CuCl₂]^? seems to activate the CH bond of the C₅H₅ rings, which results in the addition of the [(C₅H₅)(C₅H₄)ReH]⁺ hydride ion.     

Bis(di-tert-butylcyclopentadienyl)ytterbium(ii). Synthesis and catalytic properties

Polymeric (Cp₂Yb·THF) _n (1), ionicate-complex Cp₃YbNa (2), and mono-adduct (Bu^t ₂C₅H₃)₂Yb·THF (3) were prepared through a reaction of CpNa (Cp = C₅H₅ or C₅H₃Bu^t ₂) with Ybl₂ in THF. Cooling complex (3) in THF at –100 °C gives a bis-adduct, which reversibly dissociates to give the mono-adduct, The (Bu^t ₂C H , Yb·THF complex shows catalytic activity in the homogeneous hydrogenation of hex-l-ene and in the polymerization of styrene.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No, 7, pp. 1833–1837, July, 1996.     

Metal complexes as phase transfer catalysts in the synthesis of O-acetylmandelonitrile

The asymmetric synthesis of O-acetylated mandelonitrile derivative was accomplished from PhCHO, KCN, and Ac₂O in a toluene--water system in the presence of transition metal complexes of Schiff"s bases as phase transfer catalysts.     

Modulation of photosystem II chlorophyll fluorescence by electrogenic events generated by photosystem I.

In an attempt to uncover electric field interactions between PS I and PS II during their functioning, fluorescence induction curves were measured on hydroxylamine-treated thylakoids of Chenopodium album under conditions ensuring low and high levels of photogenerated membrane potentials. In parallel experiments with Peperomia metallica chloroplasts, the photocurrents were measured with patch-clamp electrodes and served as indicator of electrogenic activity of thylakoid membranes in continuous light. Inhibition of linear electron flow at PS II donor side by hydroxylamine (0.1 mM) eliminated a slow rise of chlorophyll fluorescence to a peak level and suppressed photoelectrogenesis. Activation of PS I-dependent electron transport using cofactors of either cyclic (phenazine methosulfate) or noncyclic electron transport (reduced TMPD or DCPIP in combination with methyl viologen) restored photoelectrogenesis in hydroxylamine-treated chloroplasts and led to reappearance of slow components in the fluorescence induction curve. Exposure of thylakoids to valinomycin reduced the peak fluorescence in the presence of KCl but not in the absence of KCl. Combined application of valinomycin and nigericin in the presence of KCl exerted stronger suppression of fluorescence than valinomycin alone but was ineffective in the absence of KCl. In samples treated with hydroxylamine and PS I cofactors (DCPIP/ascorbate and methyl viologen), preillumination with a single-turnover flash or a multiturnover pulse shifted the induction curves of both membrane potential and chlorophyll fluorescence to shorter times, which confirms the supposed influence of PS I-generated electrical field on PS II fluorescence. A model is presented that describes modulating effect of the membrane potential on chlorophyll fluorescence and roughly simulates the fluorescence induction curves measured at low and high membrane potentials.     

The stiffness problem for stochastic systems and a method of solving it

Using exact or approximate first integrals of the so-called truncated system of differential equations, it is shown that it is possible to improve the stability of the numerical analysis of dynamical systems described by stiff stochastic differential equations. A numerical example is given.     

Synthesis of derivatives of pyrazolo[3,4-d]pyrimidin-3-ylacetic acid and their nucleosides

3-Cyanomethyl-4,6-dimethylmercaptopyrazolo[3,4-d]pyrimidine was synthesized on the basis of 3-cyanomethyl-4-cyano-5-aminopyrazole. Ribosylation of this product gave 1-(2,3,5-tri-O-acetyl--D-ribofuranosyl)-3-cyanomethyl-4,6-dimethylmercaptopyrazolo[3,4-d]pyrimidine in 63% yield and small amounts of the 1- and 2- isomers. A number of derivatives of 6-methylmercaptopyrazolo[3,4-d]pyrimidin-3-ylacetic acid and their 1-ribosides were synthesized. The 4-methylmercapto group was replaced by amino, hydrazino, oxo, N-piperidino, and N-morpholino groups. The nitrile group was saponified in an alkaline medium to carbamoyl and carboxy groups. The corresponding 4-morpholino and 4-piperidino derivatives were obtained by the reaction of 3-cyano-4,6-dimethylmercaptopyrazolo[3,4-d]pyrimidine per-O-acetylated 1--D-ribofuranoside with secondary cyclic amines. The high resistance of the 6-methylmercapto group to the action of nucleophilic agents and the higher reactivity of the 4-methylmercapto group as compared with the nitrile group are discussed. Data on the cytotoxic activity of the synthesized compounds were obtained.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 536–545, April, 1981.     

Light fragments in (C + Be) interaction at an energy of 300 MeV/nucleon

Spectra of light fragments from carbon ion fragmentation at an energy of 0.3 GeV/nucleon on a beryllium target were measured at an angle of 3.5°. The fragment spectra covered both the evaporation and cumulative regions to higher energies than in previous experiments. The spectrum slope parameters characterizing the temperature of expanding matter in these regions were determined for protons and deuterons.