Cu-catalyzed N- and O-arylation of 2-, 3-, and 4-hydroxypyridines and hydroxyquinolines

With use of Cu-based catalysts, 2- and 4-hydroxypyridines were N-arylated in modest to excellent yields. In the case of 2-hydroxypyridine, the use of 4,7-dimethoxy-1,10-phenanthroline, 3, expanded the scope of previous literature reports to include the use of N-containing heteroaryl halides, and 2-substituted aryl halides. In addition, by using a copper catalyst based on 2,2,6,6-tetramethylheptane-3,5-dione, 4, the first N-arylations of 4-hydroxypyridines and O-arylations of 3-hydroxypyridines with aryl bromides and iodides have been accomplished. [reaction: see text].     

IR spectra and structure of 2-aryl-3-hydroxypyridines

The IR spectra of methyl, chloro, and phenyl derivatives of 3-hydroxypyridines in CCl₄ solutions and in the crystalline state were studied. A comparison of the frequencies, half widths, and integral intensities of the bands of the stretching vibrations of the hydroxyl groups in the spectra of solutions of the 3-hydroxypyridine derivatives in CCl₄ with the characteristic OH bands in the spectra of phenols demonstrates that 3-hydroxypyridines exist practically completely in the hydroxy form in dilute CCl₄ solutions. The shift in the OH bands in the spectra of 2-phenyl-3-hydroxypyridine derivatives indicates that the OH group forms a -hydrogen bond with the phenyl ring. The presence also of a band of a free OH group is evidence for the existence of s-cis and s-trans conformers relative to the C-O bond.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 187–190, February, 1972.     

Electronic structure and spectrum of UO2 2+ and UO2Cl4 2-

A theoretical study is presented of the electronic spectra of the UO(2) (2+) and UO(2)Cl(4) (2-) ions, based on multiconfigurational perturbation theory (CASSCF/CASPT2), combined with a recently developed method to treat spin-orbit coupling [P.-A. Malmqvist et al., Chem. Phys. Lett. 357, 230 (2002); B. O. Roos and P.-A. Malmqvist, Phys. Chem. Chem. Phys. 6, 2919 (2004)]. The results are compared to the experimental spectroscopic data obtained for uranyl ions in Cs(2)UO(2)Cl(4) crystals from Denning [Struct. Bonding (Berlin) 79, 215 (1992)] and to previous theoretical calculations performed using a combined configuration-interaction spin-orbit treatment [Z. Zhang and R. M. Pitzer, J. Phys. Chem. A 103, 6880 (1999); S. Matsika and R. M. Pitzer, J. Phys. Chem. A. 105, 637 (2001)]. As opposed to the latter results, the calculations performed in this work point to a significant effect of the weakly bound equatorial chlorine ligands on the excitation energies.     

Electronic structure and optical properties of monoclinic clinobisvanite BiVO4

Monoclinic clinobisvanite bismuth vanadate is an important material with wide applications. However, its electronic structure and optical properties are still not thoroughly understood. Density functional theory calculations were adopted in the present work, to comprehend the band structure, density of states, and projected wave function of BiVO(4). In particular, we put more emphasis upon the intrinsic relationship between its structure and properties. Based on the calculated results, its molecular-orbital bonding structure was proposed. And a significant phenomenon of optical anisotropy was observed in the visible-light region. Furthermore, it was found that its slightly distorted crystal structure enhances the lone-pair impact of Bi 6s states, leading to the special optical properties and excellent photocatalytic activities.     

Electronic structure and stability of AlnPn (n = 2-4) clusters

The geometry, electronic configurations, harmonic vibrational frequencies, and stability of the structural isomers of aluminum phosphide clusters have been investigated using the density functional theory. For dimers and trimers, the lowest energy structures are cyclic (IIs, IIIs) with D(nh) symmetry. The caged structure with Td symmetry (Xs) lie lowest in energy among the tetramers. The Al--P bond dominates the structures for many isomers so that one preferred dissociation channel is loss of the AlP monomer. The hybridization and chemical bonding in the different structures are also discussed. Comparisons with silicon and boron nitride clusters, the ground state structures of Al(n)P(n) clusters are analogous to those of their corresponding Si(2n) counterparts. This similarity follows the isoelectronic principle.     

Synthesis of 2, 4, 6-trialkyl-3-hydroxypyridines

Summary A new method was proposed for the synthesis of 2,4,6-trialky1-3-hydroxypyridines by the reactions of 3,5-dialkyl-2-acylfurans with ammonia.     

Nitration of 2- and 5-benzyl-3-hydroxypyridines and their N-oxides

The nitration of 2- and 5-benzyl-3-hydroxpyridines and their N-oxides takes place in the para position of the phenyl ring. The introduction of an N-oxide group into the Β-pyridol ring does not affect the orientation of substitution.     

Mass spectra of 2- and/or 6-alkyl-3-hydroxypyridines

The mass spectra of 2- and/or 6-aIkyI-3-hydroxypyridines were measured. The fragmentation processes include the loss of 1, 28 and 29 u and RCN from the molecular ions. Among the characteristic ions, the [M – 1]⁺ ions are the base peak for all of the ethyl-containing pyridines. According to a labelling study, the hydrogen on the β-caroon is the major contributor to the formation of [M – 1]⁺.     

Chemistry of 2-aryl-substituted 3-hydroxypyridines

Russian Chemical Bulletin -     

Tautomerism of 6- and 2-(arylazo)-3-hydroxypyridines in aprotic polar solvents

On the basis of calculations of the basicities of possible protonation sites, electronic spectra, and potentiometric titration, it has been shown that 6- and 2-(arylazo)-3-hydroxypyridines exist in nitromethane and acetonitrile in the hydroxyazo-form, and are protonated at the pyridine nitrogen atom.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1656–1661, December, 1984.     

Electronic structure and disorder in NaxCoO2 and SrRh2O4

We discuss the electronic structure of Na_xCoO₂ from the point of view of first principles electronic structure calculations. The band structure contains low spin Co ions, with average charge 5 + x leading to a nearly full Co t_2g manifold. The bands corresponding to this manifold are narrow and separated from the O 2p bands and from the e_g bands, which are also narrow. There are two main sheets of Fermi surface, a large section derived from a_g symmetry states and small hole pockets. We find significant effects due to Na disorder on these small sections, with the result that they should be localized. This is discussed in relation to recent photoemission experiments. For comparison, we present a virtual crystal band structure of beta-SrRh₂O₄. Like Na_xCoO₂ it shows a large crystal field gap between narrow t_2g and e_g manifolds, but because of its stoichiometry is a semiconductor rather than a high carrier density metal.     

Crystal structure and luminescence properties of 4-(4-benzoyloxy-2-hydroxyphenyl)-2,2-difluoro-6-phenyl-1,3,2-dioxaborine

The crystal structure of 4-(4-benzoyloxy-2-hydroxyphenyl)-2,2-difluoro-6-phenyl-1,3,2-dioxaborine (1) was determined by X-ray diffraction analysis. π-π-Stacking interaction between the molecules results in joining the molecules into a three-dimensional layered framework. Luminescence of the aggregates is observed in concentrated solutions of compound 1. Two routes of excimer formation in crystal were revealed by steady-state and time-resolved luminescence spectroscopy: via excitation of single molecules and via excitation of aggregates.     

金属硼烷arachmo—P4M2B8和closo—MB10X2分子结构的键合研究

利用ＤＶ－Ｘα法计算了ａｒａｃｈｎｏ－（ＰＨ３）４Ｍ２Ｂ８Ｈ８（ｕ－Ｈ）２（Ｍ：Ｎｉ,Ｐｄ,Ｐｔ）和ｃｌｏｓｏ－（ＰＨ３）２ＭＢ１０Ｈ８Ｘ２（Ｍ：Ｆｅ,Ｒｕ,Ｏｓ;Ｘ：Ｃｌ,Ｂｒ,Ｉ,ＯＨ,Ｌｉ）系列分子的电子结构。结果表明在２类ａｒａｃｈｎｏ－Ｐ４Ｍ２Ｂ８和ｃｌｏｓｏ－ＭＢ１０Ｘ２主干结构中均有类似的２种Ｍ－－Ｂ键合：一是金属原子ｄ轨道相对配体原子轨道形成了全对称匹配分子轨道（ＭＯｓ）;二是部分