Elektrophile Substitution und nucleophile Addition an 3,4-Dihydro-5(1H)-pyrromethenonen

3,4-Dihydro-5(1H)-pyrromethenones are easier attacked at themeso-position by electrophiles than 5(1H)-pyrromethenones. This is demonstrated both by aMannich-type-substitution or deuterium-exchange-experiments and by the addition of O-, S-, and N-Nucleophiles to the exocyclic double bond of the model-dihydropyrromethenone (Z)-1 under very mild reaction conditions. Applying these results to the chemistry of 2,3-dihydro-bilatrienes-abc, their chemical characteristics—especially their tautomeric behavior and their dominant C-5-selectivity towards electrophiles—become better understandable.

     

Short Te …︁ Te bonding contacts in a new layered ternary telluride: Synthesis and crystal structure of 2D Nb3GexTe6 (x ≃ 0.9)

The new layered ternary compound Nb₃Ge_xTe₆ (x ? 0.90) was prepared by direct combination of the elements taken in the stoichiometric proportions 3 : 1 : 6, heated at 1 000 °C for 10 days in silica tubes and quenched to room temperature. The phase crystallizes in the orthorhombic symmetry, space group Pnma (#62), with the following single crystal refined parameters: a = 643.18(5) pm, b = 1391.98(11)pm and c = 1 154.07(5) pm, with Z = 4. The structure was refined to an R of 3.4% (R_w = 4.6%), with 1969 independent reflexions and 49 parameters. The structure is based on the close stacking of trigonal prismatic (TP) slabs in the AA/BB mode. The slabs can be seen as built up from face sharing biprisms, which are filled either by one or by two niobium cations situated in the middle of the trigonal prisms. The germanium is located in the middle of the common face of two prisms, leading to a rather unusual anionic square coordination. The refinements showed that this latter cation does not fill completely its square site. No cation was found in the van der Waals gap between the slabs. The mean d_{Ge? Te} distance (276.5 pm) is in agreement with Ge^II cations, while some Te …? Te distances (from 333.84 to 361.65pm) are too short for anions in a simple contact. These bonding distances, already mentionned in some MTe₂ compounds, are to be ascribed to charge transfer in the structure, with a partial oxidation state for the tellurium anions. Short Nb? Nb and Nb? Ge distances (292.0 and 281.3 pm, respectively) imply intercationic bonding within the slabs.     

Effect of arrangement of the styryl fragment on the optical properties and complexation of mono-and bis(styryl)-substituted <Emphasis Type="Italic">N</Emphasis>-methylpyridinium perchlorates containing benzo-15-crown-5 ether moieties

Using ¹H NMR spectroscopy and steady-state and time-resolved electronic spectroscopy, the optical properties of mono-and bis(styryl)pyridinium perchlorates and their complexes with Mg²⁺, Ba²⁺ cations were studied. The stability constants of the complexes were determined using spectrophotometric titration. The formation of inclusion complexes for Mg²⁺ and sandwich type complexes for Ba²⁺ results in fluorescence enhancement and increases the lifetimes of the excited states of the initial bis-styryl ligands. The variation of position of the styryl fragment in the pyridinium aromatic ring gives rise to photochromic crown ethers with different optical and photophysical characteristics and is also an easy route to bis(crown-ethers) of symmetrical and unsymmetrical structure. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2092–2100, November, 2007.     

Synthesis and biological activity of novel 2-(3-trifluoromethylphenoxy)-4-trifluoromethylthiazole-5-carboxamide derivatives

Novel 2-(3-trifluoromethylphenoxy)-4-trifluoromethylthiazole-5-carboxamides were designed and synthesized utilizing ethyl 3-amino-4,4,4-trifluoro-2-butenoate as a starting material via six steps. Subsequently, their biological activities were evaluated in the greenhouse. Results indicated that several compounds have some insecticidal or fungicidal activity at 600 g ai/ha and 300 g ai/ha, respectively.     

Reactions of regioisomeric fluoroalkyl-containing β-aminovinyl ketones with hydrazines

Fluoroalkyl -alkyl--aminovinyl ketones react with hydrazine hydrate to give the respective razoles and with phenylhydrazine they form a mixture of pyrazoles and 5 hydroxy-²-pyrazolines. Alkyl(aryl) -fluoroalkyl--aminovinylketones do not react with the hydrazines mentioned above. With 2,4-dinitrophenylhydrazine, both types of fluoroalkyl-containing -aminovinyl ketones give only hydrazones of the corresponding methyl alkyl(aryl) ketones.     

Ab initio and DFT studies on tautomerism of indazole in gaseous and aqueous phases

Electronic structure of optimized Ge₅, Ge₁₇, Ge₅–O and Ge₅ embedded in SiO₂ nanoparticles have been studied by density functional theory to find out the effect of cluster size and Ge–O bond(s) on the optical energy gap between LUMO and HOMO. It was found that the optical energy gap depends on both cluster size and the number of Ge–O bonds nonlinearly. The optical energy gap was found to be in visible light range when the Ge₅ nanoparticle has been embedded in SiO₂ matrix.     

Novel chemical modifications at the 4-position of chromones. Synthesis and reactivity of 4H-chromene-4-spiro-5′-isoxazolines and related compounds

Reactions of chromones with dilithiooximes proceed via nucleophilic 1,2-addition to give, on acidification, 4H-chromene-4-spiro-5′-isoxazoline derivatives in high yields. On treatment with concentrated H₂SO₄ the isoxazoline ring of this novel spiroannulated heterocyclic system opens to give α,β-unsaturated oximes, which undergo nitrosation, bromination, and the Beckmann rearrangement to the corresponding spiroisoxazolines and α,β-unsaturated amides, respectively. The latter can be obtained directly by the Beckmann rearrangement of 4H-chromene-4-spiro-5′-isoxazolines.     

Carboxylic Acids from <Emphasis Type="Italic">Phyllanthus urinaria</Emphasis>

Five compounds, terephthalic acid mono-[2-(4-carboxy-phenoxycarbonyl)-vinyl] ester (1), (E)-3-(5′-hydroperoxy-2,2′-dihydroxy[1,1′-biphenyl]-4-yl)-2-propenoic acid (2), 3,4,5-trihydroxybenzoic acid (3), succinic acid (or butanedioic acid) (4), and 2,3,4,5,6-pentahydroxybenzoic acid (5), were isolated from Phyllanthus urinaria. The structures of these compounds were elucidated by means of spectral techniques including IR, MS, and 1D/2D NMR. 1 and 2 are new compounds.__________Published in Khimiya Prirodnykh Soedinenii, No. 1, pp. 14–17, January–February, 2005.     

5-氟尿嘧啶-1-乙酸合铜(Ⅱ)的合成及其与DNA的作用

The 5-fluorouracil-1-acetic acid (5FuAA) and its Cu(Ⅱ) complex (5FuAACu) were synthesized and the date for the crystal complex was obtained. The interaction of 5-fluorouracil-1-acetic acid (5FuAA) and its Cu(Ⅱ) complex (5FuAACu) with DNA was also investigated by using spectral, viscometric, electrochemical and agarose gel electrophoresis methods. The results of interaction with DNA suggest that both 5FuAA and 5FuAACu can bind to DNA in a static electricity attraction mode. But the attraction of 5FuAACu is greater than that of 5FuAA.     

A new synthesis of trifluorinated compounds via 1,1-dichloro-1-alkenes in superacid

A two step process for converting ketone or aldehyde via 1,1-dichloro-1-alkenes to the corresponding 1,1,1-trifluoroderivatives is described, based on HF addition and chlorine-fluorine exchange under superacidic conditions.