Convenient and Scalable Process for the Preparation of Indole via Raney Nickel–Catalyzed Hydrogenation and Ring Closure

An efficient and practical method for the synthesis of indole as a key starting material for many useful chemicals is described. Using 2-nitrotoluene as starting material, hydroxymethylation with formaldehyde under alkaline conditions gave 2-(2-nitrophenyl)ethanol on a large scale. Raney Ni catalyst was used for both reduction of the nitro group as well as for the indole formation. The overall yield was 78% from 2-nitrotoluene.     

Improving the Catalytic Performance of the Hydrogen Evolution Reaction of α-MoB2 via Rational Doping by Transition Metal Elements

Abundant transition metal borides are emerging as promising electrochemical hydrogen evolution reaction (HER) catalysts which have a potential to substitute noble metals. Those containing graphene-like (flat) boron layers, such as α-MoB2, are particularly promising and their performance can be further enhanced via doping by the second metal. In order to understand intrinsic effect of doping and rationalize selection of dopants, we employ density functional theory (DFT) calculations to study substitutional doping of α-MoB₂ by transition metals as a route towards systematic improvement of intrinsic catalytic activity towards HER. We calculated thermodynamic stability of various transition metal elements to select metals which form a stable ternary phase with α-MoB₂. We inspected surface stability of dopants and assessed catalytic activity of doped surface through hydrogen binding free energy at various hydrogen coverages. We calculated the reaction barriers and pathways for the Tafel step of HER for the most promising dopants. The results highlight iron as the best dopant, simultaneously lowering the reaction barrier of the Tafel step while having suitable thermodynamic stability within MoB₂ lattice.     

Circular Dichroism of Transition Metal Complexes and Sugar Derivatives Having a Free 1,3-Diol System or “Isolated” Hydroxyl Group

Abstract

Heptofuranose derivatives 1–6 having free 1, 3-diol systems form in situ complexes with Mo₂(OAc)₄ whose CD spectra permit the assignment of absolute configuration at C-5 using a sector rule proposed by G. Snatzke.^2–6 The interpretation of CD spectra of analogous complexes formed from derivatives 7–12 was more complicated and did not lead to direct configuralional conclusions. CD spectra of complexes formed from Rh₂(CF₃COO)₄ and sugar derivatives 13–21, containing an “isolated” hydroxyl group, permit the assignment of absolute configuration. Conclusions were corroborated by the investigation of CD spectra of rhodium complexes with compounds 22–27.     

X—ray Study on the Ring—substituted Phthalocyanines：Crystal Structure of Metal Free,1,4,8,11,15,18,22,25—Octa—butyloxyphthalocyanine

<正>The crystal structure of 1,4,8,11,15,18,22,25-octa-butyloxyphthalocyanine was determined by X-ray diffraction methods. The crystal is of triclinic, space group P 1 with a = 14.0780(3), b = 14.3480(4), c = 17.0090(2) A, α = 72.156(2), β = 86.193(2), r= 73.655(2)°, C64H82N8O8, Mr = 1091.38, Z = 2, V = 3137.5(1) A3, Dc= 1.155 g/cm3, F(000) = 1172, μ(MoKα) = 0.077 mm-1, the final R = 0.0787 and wR = 0.2240 for 5795 observed reflections with I ≥ 2σ(I). The steric congestion between the neighboring butyloxy groups distorts the core of phthalocyanine into a saddle shape conformation. In the crystal lattice, molecules overlap to each other with π-π interaction but the extent of overlap is different along the three axial directions.     

Optical response of a nematic liquid crystal cell at the splay – bend transition: a model and dynamic simulation

We study the dynamical optical response of a nematic liquid crystal cell that undergoes the splay–bend transition after applying a voltage across the cell. We formulate a simplified model that takes into account both the flexoelectric coupling and the surface rotational viscosity. The dynamic equations of the model are solved numerically to calculate the temporal evolution of the director profile and of the transmittance. We evaluate the response time as a function of a number of parameters, such as dielectric and elastic anisotropies, asymmetry of the surface pretilt angles, anchoring energy, surface rotational viscosity and flexoelectricity.     

Kinetics of the Dissociation of Transition Metal Complexes with α,α-Dipyrrolylmethene in Acetic Acid–Benzene as a Binary Proton-Donating Solvent

The kinetics of the dissociation of Co(II), Ni(II), and Zn(II) complexes with 4,4-dibutyl-3,3,5,5-tetramethyldipyrrol-2,2-ylmethene was studied in acetic acid–benzene as a binary proton-donating solvent. The metal nature was found to affect the kinetic parameters of the process. Assumptions were made about the limiting step of the process and the effectiveness of d metal ions in the template synthesis of porphyrins from dipyrrolylmethenes.     

Cyclopenta[b]thienyl Ligand in Organometallic Chemistry. Synthesis of Cyclopenta[b]thiophene η5-Complexes with Metal Coordination at the Thiophene Ring

Unlike isoelectronic ⁶-indenyl ruthenium, manganese, and chromium complexes, heating of Mn(CO)₅OTf, [Ru(Cp^*)Cl₄], and Cr(C₁₀H₈)(CO)₃ with isomeric 2-ethyl-5-methylcyclopenta[b]thiophenes leads to the corresponding ⁵-complexes where the metal is coordinated at the C₅-carbocycle. The structure of the complex Mn(Th)(CO)₃ (Th = 2-ethyl-5-methylcyclopenta[b]thienyl) was proved by X-ray analysis.     

Synthesis of a protected ribonucleoside phosphoramidite-linked spin label via an alkynyl chain at the 5′ position of uridine

New, spin-labeled nucleosides, and an efficient synthetic route for a modified uridine amidite, were developed. The spin-labeled part was the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) group, which was linked via an alkynyl chain at the 5 position of uridine. Three typical protecting groups, the t-butyldimethylsilyl (TBDMS) group at 2′, the dimethoxytrityl (DMTr) group at 5′, and the phosphoramidite group at 3′, were introduced to produce an automated nucleic acid synthesizer. The TEMPO group at the 5 position in the uridine structure affected introduction of bulky protecting groups, such as the DMTr group at the 5′ position and the TBDMS group at the 2′ position. The electron paramagnetic resonance (EPR) data revealed a nitroxyl radical in the structure of synthetic nucleoside compounds; however, RNA produced by automated synthesis using a TEMPO-linked uridine phosphoramidite building block was EPR silent.     

Free radical intervention,deamination and decarboxylation in the ruthenium(III)-catalysed oxidation of L-arginine by alkaline permanganate – a kinetic study

The kinetics of the Ru^III catalysed oxidation of L-arginine by alkaline permanganate was studied spectrophotometrically using a rapid kinetic accessory. The reaction follows a two stage process. In both the stages the reaction is first order with respect to [oxidant] and [catalyst] with an apparent less than unit order in [substrate] and [alkali]. The data suggest that oxidation proceeds via formation of a complex between the active Ru^III species and L-arginine, which then reacts with one mole of permanganate in a slow step to yield a L-arginine free radical, followed by a fast step to form the products. The reaction constants involved in the mechanism were evaluated. There is a good agreement between observed and calculated rate constants under different experimental conditions for both stages of reaction. The activation parameters for the slow step were calculated and are discussed.     

Synthesis of the Aliphatic Subunit of the Macrolide LL‐Z 1640‐2 via Vasella Ring Opening of a 6‐Iodo‐4‐deoxy‐D‐mannose

The synthesis of the aliphatic subunit 9 of the macrolide LL‐Z1640‐2 (I), starting from a 4‐deoxy‐D‐mannose derivative 2a, is described. The procedure includes the first successful application of a Vasella ring opening reaction for a 4‐deoxypyranoside. Nucleophilic addition of an alkynyllithium reagent to the aldehyde 4 led to the propargylic alcohol 7, which was converted to the advanced building block 9 in two further steps.     

Electron transfer – ion insertion electrochemistry at an immobilised droplet: probing the three-phase electrode-reaction zone with a Pt disk microelectrode

A four-electrode setup was used to study the following system: a nitrobenzene (NB) drop containing no added supporting electrolyte and either ferrocene or decamethylferrocene was placed on a glassy carbon disk and surrounded by an aqueous solution of supporting electrolyte. The glassy carbon electrode was polarised appropriately to generate either the ferrocenium or the decamethylferrocenium cations. A very thin conical-body Pt microdisk electrode was placed inside the NB drop to detect the product cations. The relation between the time of appearance of the reduction current at the microelectrode and the distance from the three-phase junction indicates that the electrode reaction starts at this junction where both the electron transfer and the ion transfer can take place.     

Taphonomy of prehistoric bark in a salt environment at the archaeological site in Hallstatt,Upper Austria – An analytical approach based on FTIR spectroscopy

Taphonomy of subfossil bark was assessed in Hallstatt, Upper Austria. Samples from the Bronze Age were compared with recent corresponding material from the same site. Preservation of the prehistoric samples was caused by storage in a salt and clay mixture. FTIR spectroscopy was used to determine differences in material chemistry. Principal Component Analysis was applied to display the segregation of the data set according to the different factors and to display the strength of the effects. Results revealed that deacetylation processes dominated aging processes. Focusing on two band regions at around 1730 and 1230 cm⁻¹ a clear separation was achieved. Additionally some samples were selected for further analyses to investigate the influence of the inorganic matrix. Thermal analyses demonstrated an ash content of more than 15%_mass. X-ray diffractometry revealed the presence of salt (dominant), gypsum, pyrite, quartz, and calcite minerals.     

Adhesive-Strength Evaluation via the <Emphasis Type="Italic">Pull-Out</Emphasis> Method in a Binder—Elementary-Filament System at Various Treatments of Filaments

The adhesive strength of binders with elementary filaments that have been used for the production of LUP carbon tape covered by different types of coatings is evaluated via the pull-out method. Two types of single-layer coatings are considered, one of which is based on titanium of the VT1-0 brand while the other is made of 12Kh18N10T steel, as well as a bilayer coating composed of a titanium layer coated by a stainlesssteel layer. The adhesive strength is determined for thermoreactive (epoxy with amine hardener) and thermoplastic (polyamide) types of binders. The best adhesive strength (more than 30%) of binders is achieved when the LUP carbon tape is covered with stainless steel.