Use of azolium ylides in the synthesis of con-densed heterocyclic systems from 2-quinox-alylacetonitriles

The reaction of -substituted 2-quinoxalylacetonitriles with 1-alkyl(aryl)imidazoles, -benzimidazoles, -1,2,4-triazoles and 5,6-dihydroimidazo[i,j]quinoline was studied. It was found that during the course of the reaction an unusually easy dealkylation of the azole ring takes place, while the aryl substituent is not split off. A reaction mechanism has been proposed including the formation of an ylide intermediate, followed by subsequent electrophilic attack on the C₍₂₎ position of the azolium ring. The applicability boundaries of the reaction studied and the spectral characteristics of the synthesized compounds were investigated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 224–229, February, 1993.     

Isomerisation in the chemistry of platinacyclobutane complexes

The platinacyclobutane complexes PtCl₂L₂(C₃H₅Me)], L  pyridine, CD₃CN, or tetrahydrofuran, exist as mixtures of isomers containing P$\text{tCH}{}_2\text{CHMeC}$H₂ or P$\text{tCHMeCH}{}_2\text{CH}{}_2$ groups in rapid equilibrium. Decomposition occurs in some cases to give [PtCl₂L(CH₃CH₂CHCH₂)]. Stereospecific skeletal isomerisation also occurs in metallocyclobutanes containing the groups P$\text{tCHRCHRC}$H₂  P$\text{tCHRCH}{}_2\text{C}$HR, when R  aryl further decomposition gives ν-allylplatinum complexes.     

Isothermal degradation of poly-2,2′-(m-phenylene)-5,5′-bibenzimidazole

The isothermal degradation of poly-2,2′-(m-phenylene)-5,5′-bibenzimidazole in vacuo has been studied. Measurement of the increase in pressure with time, coupled with infrared analysis, was used to determine the distribution of the degradation products. Processes A and B with different second-order rate laws were determined to be significant in the temperature range of 550–700°C. Process A leads to the formation of equimolar quantities of hydrogen and ammonia and has an activation energy of 68 kcal/mole. Process B leads to the production of HCN, NH₃, and H₂ in the ratio of 1:1:2.5 and has an activation energy of 77 kcal/mole. The activation energies and the rate laws are consistent with a mechanism in which the initial degradation step is the bimolecular reaction of two aromatic rings.     

Synthesis, tautomeric states and crystal structure of (Z)-ethyl 2-cyano-2-(3H-quinazoline-4-ylidene) acetate and (Z)-ethyl 2-cyano-2-(2-methyl-3H-quinazoline-4-ylidene) acetate

The new compounds (Z)-ethyl 2-cyano-2-(3H- and 2-methyl-3H-quinazoline-4-ylidene) acetate (1 and 2, respectively) were synthesized by multi-step reactions. The structures in a solution have been determined by (1)H-NMR spectroscopy and in the crystal form by X-ray analysis. Molecule 1 crystallized in a primitive monoclinic cell, space group capital ER, P2(1/c). The cell dimensions are a=7.970(6) A, b=7.061(2) A, c=20.537(7) A, beta=97.69(5) degrees , V=1145.3(10) A(3). Molecule 2 crystallized in a triclinic cell, space group P-1, the cell dimensions are a=8.196(5) A, b=8.997(6) A, c=9.435(4) A, alpha=74.22(4) degrees, beta=89.75(4) degrees , gamma=74.07(5) degrees , V=641.9(6) A(3). In both compounds the presence of intra-molecular NH---O=C hydrogen bonding between the nitrogen atom in position 3 of the quinazoline ring and a carbonyl group of the ethyl cyanoacetate residue was proven by quantum-chemical, (1)H-NMR and X-ray methods.     

Overlapping spheres multiple scattering Xα calculations of the ionization potentials and electron affinities of nitrogen oxides

The ionization potentials and electron affinities of a series of nitrogen oxygen compounds have been calculated by the overlapping spheres MS Xα method to assess its applicability on a series for which good experimental data is available. The results for the ionization potentials were satisfactory although a straightforward matching of calculated and experimental IP's without consideration of other criterion would have led to some misassignments. The results for the electron affinities are in excellent agreement with experiment.     

On the synthesis of the N2F+5 cation. A critical comment on the paper by Toy and Stringham.

Toy and Stringham recently reported [1] the synthesis of N₂F⁺₅ (CF₃)₃CO^-, a salt containing the novel pentafluorohydrazinium cation. This cation would be of significant academic and practical interest [2] since it would constitute the first known example of a substituted NF⁺₄ cation, i.e. an NF⁺₄ cation in which a fluorine ligand is replaced by an NF₂ group. According to the authors of [1], N₂F⁺₅(CF₃)₃CO^- was formed in a very unusual reaction involving the transfer of a fluorine cation from (CF₃)₃COF to N₂F₄ according to:

     

Synthese und Röntgenstrukturanalyse des 8π-Elektronenringsystems S4N4O2Sn2(CH3)6 und des magnetische Verhalten von S4N4O2 und S8N8O4

Synthesis and X-Ray Structure Analysis of the 8π-Electron-Ring-System S₄N₄O₂Sn₂(CH₃)₆ and the Magnetic Properties of S₄N₄O₂ and S₈N₈O₄ S₄N₄O₂ reacts with N[Sn(CH₃)₃]₃ in a molar ratio of 1:1 to an eight-membered trimethyltin-substituted 8π-electron skeleton, S₄N₄O₂Sn₂(CH₃)₆. In contrast to known 6π-electronsystems this compound has tin atoms which are tetracoordinated. This was demonstrated on the basis of an x-ray analysis. S₄N₄O₂Sn₂(CH₃)₆ · 1/2 C₆H₆ crystallizes in the space group P2₁/c with a = 1396.0(4), b = 1190.3(4), c = 1256.7(3) pm, and β = 103.46(2)°. It was shown that the ability of coordination at the tin atom depends on the electron density. The magnetic properties of S₄N₄O₂ and S₈N₈O₄ were investigated by the Faraday method. The high diamagnetism in these ring compounds is caused by the π-electrons.     

Direct detection of the biradicals generated in the Norrish type II reaction

The biradicals generated in the Norrish type II reaction from the triplet manifold have been observed using laser flash photolysis techniques. The spectra and extinction coefficients closely resemble those of typical ketyl radicals. Typical lifetimes are in the 40–100 ns range depending on the solvent. Their interaction with oxygen is essentially diffusion controlled.     

Zum thermischen Verhalten von Li3MnO4. II [1, 2]. Über α- und β- Li2MnO3

Thermal Behaviour of Li₃MnO₄. II. α- and β-Li₂MnO₃ By thermal decomposition of Li₃MnO₄ we obtained two new forms of Li₂MnO₃: α-Li₂MnO₃ crystallizes due to Guinier-Simon photographs cubic face-centered with a = 4.09₂ Å, β-Li₂MnO₃ hexagonal with a = 4,93, c = 14.24 Å, c/a = 2.89. α-Li₂MnO₃ is paramagnetic with μ = 3,82 B.M. Below the Neel temperature (≈? 50 K) β-Li₂MnO₃ is antiferromagnetic. Effective Coordination Numbers, ECoN, are calculated and discussed.