New synthesis of 7-bromo-1, 3-dihydro-3-hydroxy-5-(2′-pyridyl)-2H-1,4-benzodiazepin-2-one

A new synthesis of 7-bromo-1,3-dihydro-3-hydroxy-5-(2′-pyridyl)-2H-1,4-benzodiazepin-2-one ( 5 ) is described. Starting from bromazepam ( 3 ), C(3) acylation with lead tetraacetate/potassium iodide in acetic acid affords 4 , while its mild hydrolysis according to our recently described method (5) gives 5 . Improved hexamine cyclization of 1 into 3 , via quaternary hexaminium salt 2 , is discussed, and identification of the intermediates 7 and 8 is performed. Compound 5 undergoes on melting, or on brief heating in glacial acetic acid, the thermal rearrangement into quinazolin-2-aldehyde ( 13 ), the structure of which is confirmed by oxidation into the ester 14 , which in turn was hydrolyzed to the acid 15 . The same compound ( 5 ) rearranges on heating with manganese(III) acetate in acetic acid into the 3-amino-2-quinolone derivative 6 . On heating in glacial acetic acid in the presence of lead tetraacetate/potassium iodide (or iodine), compound 4 , in addition to giving the aldehyde 13 , ester 14 and acid 15 rearrangement products, affords 1,2-dihydroquinazolin-2-carboxylic acid 16 .     

Synthesis and crystal structure determination of the new ternary intermetallic phase Na17Cu6Ga46.5 (Na102Cu36Ga279)

Na₁₇Cu₆Ga_46.5 crystallizes in the trigonal system, space group with a = B = 16.183(6), C = 35.190(9) Å; Z = 6. Diffraction data were collected on a Nonius CAD 3 diffractometer within the octants hkl and of the corresponding A-centered monoclinic cell (a = 14.993(6), B = 16.184(7), C = 25.254(8) Å; β = 119.75(5)°). The 5091 reflections were transformed and averaged into 1216 observed (I> 3σ(I)) in the space group. The structure was solved by direct methods and refined by full-matrix least-squares to a final R(F) = 0.056. The structure of Na₁₀₂Cu₃₆Ga₂₇₉ contains icosahedra displaying two types of symmetry and a triply fused icosahedron which forms a very unusual polyhedral complex with a copper atom (M₂₈CuM₂₈). Clusters are linked to each other to form an intricated three-dimensional anionic lattice. Sodium cations lie inside 12-vertex (Friauf), 15-vertex, and 16-vertex polyhedral cavities. This stoichiometric phase has been interpreted in terms of electron-deficient bonding within clusters and localized (2c-2e) bonding between clusters. In association with the extended Hückel molecular orbital (EHMO) calculation, the Wade-Mingos electron counting procedure applies successfully.     

Synthesis and Crystal Structure of M11X10 Compounds, M=Sr, Ba and X=Bi, Sb. Electronic Requirements and Chemical Bonding

The intermetallic compounds Sr₁₁Bi₁₀, Ba₁₁Bi₁₀, and (Sr₅Ba₆)Sb₁₀ have been obtained from melts of mixtures of the elements. They crystallize in the tetragonal system, space group I4/mmm, Ho₁₁Ge₁₀ structure type, tI84 Pearson symbol, Z=4, with cell parameters a=12.765(3), 13.230(3), 12.748(2) Å and c=18.407(3), 19.365(3), 18.761(2) Å, respectively. The structures were solved from single-crystal X-ray data and refined by full-matrix least-squares to R1=6.71, 5.44, and 5.73%. The structure of M₁₁X₁₀ contains three discrete anionic moieties: square rings X⁴⁻₄, dumbbells X⁴⁻₂, and isolated X³⁻. Using formal charges the unit cell of M₁₁X₁₀ may be described as containing 44 M²⁺, 2X⁴⁻₄, 8X⁴⁻₂, and 16X³⁻ ions. This structure is discussed in comparison with other Bi or Sb pnictide compounds. Bonding is analyzed therein using molecular orbital (EHMO) calculations for the anions (dumbbell and square units) and also the periodic tight-binding method. Lone pair repulsions inside and between the anionic units are evidenced; they are compensated by strong bonding cation-to-anion interactions. Interatomic distances along the series appear to be more dependent on packing than on electronic effects.     

Grafted self-assembled monolayers derived from naturally occurring phenolic lipids

Self-assembled monolayers grafted onto silicon surfaces were obtained from the hydrosilylation products by trialcoxysilanes of naturally occurring phenolic lipid allyl ethers. The as-obtained materials were characterized by various physical and physicochemical methods. Thus, contact angles of water drops showed that they possess very high hydrophobicity. Their excellent regularity was corroborated by AFM microscopy. The frequencies of the stretching CH2 infrared modes indicate the presence of alkyl chains mainly in the trans/trans conformation. Additionally, optical ellipsometry and quartz microbalance measurements enabled us to estimate the thickness of the films. The results, as a whole, are in good agreement with the formation of densely packed monolayers.     

Time-resolved study of the oxidation of ethanol by cerium(IV) using combined quick-XANES, UV-vis, and Raman spectroscopies

Time-resolved X-ray absorption spectroscopy (Quick-XANES) has been combined with UV-vis and Raman spectroscopies to study the in situ reduction of Ce4+ to Ce3+ in ethanolic solution with a time resolution of ca. 4-5 s. For this purpose, a cam-driven oscillating double-crystal monochromator with a channel-cut crystal was combined with two spectrometers for UV-vis and Raman spectroscopies in a specialized cell which allows one to fit the optical pathways for all three spectroscopies individually. The results show that high-quality results can be obtained simultaneously, thus giving a detailed insight into the mechanisms of the investigated chemical reaction. The continuous release of nitrate and ethanol ligands from the initial Ce4+ into the solution finally leads to a trivalent cerium species which is only coordinated with water molecules after about 1800 s of reaction time.