A facile synthesis of 4-acylamino-tetrahydroindazoles via the Ritter reaction

A new route toward 4-acylamino- and 4-amino-substituted tetrahydroindazoles is disclosed. The title compounds are obtained in good to excellent yields in the Ritter reaction between 4-hydroxy-tetrahydroindazoles and various nitriles. The reactivity of the tetrahydroindazole-derived carbenium ion is both sufficiently high to react with trichloroacetonitrile and sufficiently selective to resist the azide functionality within its structure. The present approach adds a method to the toolbox of tetrahydroindazole chemistry and facilitates the structural modifications of the scaffold, which has found important applications in medicinal chemistry.     

Heating of a Compressible Liquid by a Constant Heat Flux

Several variants of the problem of heating a compressible liquid by a timeindependent heat flux are numerically studied. It is shown that, after a certain time, the pressure everywhere behind the shock wave differs only little from some constant value. Approximate analytical formulas are obtained, which demonstrate independence of pressure of thermal conductivity and some other features of the relation between the pressure and the heatflux intensity. Several examples are given, which confirm the adequacy of formulas to numerical solutions of the problem.     

Quantum-chemical study of silacyclohexanes C5H10SiHCN, C5H10SiH(t-Bu), C5H10Si(t-Bu)CN, and C5H10SiHF

By quantum-chemical calculations at the M06-2X/aug-cc-pVTZ level of theory geometrical parameters, dipole moments, polarizabilities, first hyperpolarizabilities and relative energies of the axial and equatorial conformers in gaseous phase were determined for 1-cyano-1-silacyclohexane, 1-tert-butyl-1-silacyclohexane, 1-tert-butyl-1-cyano-1-silacyclohexane, and 1-fluoro-1-silacyclohexane. For the cyano group and fluorine atom the axial position is more preferable whereas for tert-butyl group, equatorial one. Polarizabilities of conformers are similar but optical anisotropy of equatorial conformers of C₅H₁₀SiHCN and C₅H₁₀SiH(t-Bu) molecules is much larger than that of axial conformers. Upon substitution in nitriles of C¹ atom by Si atom the hyperpolarizability is many times increased.     

Synthesis and crystal structure of benzyltrimethylammonium dicitratoborate monohydrate

Benzyltrimethylammonium dicitratoborate [C₆H₅CH₂N(CH₃)₃][(C₆H₆O₇)₂B] · H₂O (I) has been synthesized and separated out in the form of single crystals for the first time. Its crystal structure has been studied by X-ray diffraction. Crystals are triclinic with a = 10.0832(2) Å, b = 11.1232(3) Å, c = 11.9617(3) Å, α = 84.874(1)°, β = 73.520(1)°, γ = 85.550(1)°, Z = 2, space group P-1. The structure has been solved by direct methods and refined by the full-matrix least-squares technique in the anisotropic approximation up to R = 0.0485 (Bruker-Nonius KappaCCD automatic diffractometer, λMoK _α). The crystal structure of compound I is based on centrosymmetric dimers that consist of complex anions and water molecules and linked by the system of hydrogen bonds into a three-dimensional framework. The crystals of compound I contains five asymmetric O-H...O hydrogen bonds. A specific feature of the structure is the formation of -COO...H...H₂O hydrogen bonds, in which the carboxyl proton is considerably shifted towards the water molecule.     

Synthesis,structure and cytotoxic activity of 2‐acetyl‐5‐trimethylsilylthiophene(furan) and their oximes

5‐Trimethylsilylderivatives of 2‐acetylthiophene and ‐furan have been regioselectively prepared by a one‐pot procedure from the corresponding 2‐acetylfuran or 2‐acetylthiophene using lithium N‐methylpiperazide (LNMP)–butyllithium–trimethylchlorosilane–water as the sequence of reagents. The ketones obtained were converted to the corresponding oximes. The structure of 2‐acetyl‐5‐trimethylsilylthiophene oxime (E‐isomer) has been studied by X‐ray diffraction. Formation of centrosymmetric dimers by means of H‐bonds has been observed. The intermolecular hydrogen bond O9? H…N8 length is 2.842(5) Å [H…N8 = 1.87 (6) Å, O9? H…N8 = 157(4)°]. Copyright © 2006 John Wiley & Sons, Ltd.     

Kinetics of Oxy-chemiluminescence and Its Use in the Analysis of Antioxidants

The influence of the antioxidant (chroman C₁, a synthetic analog of tocopherol) on the chemiluminescence kinetics during diphenylmethane and cumene oxidation is studied. Principles are considered for choosing a standard oxidized mixture in which the concentration and reactivity of an antioxidant are determined most reliably. The results of exact computer simulations and analytical calculations assuming quasi-stationarity with respect to different types of radicals are compared. A strategy is proposed to interpret the results and choose the experimental conditions (model oxidation system, type of hydrocarbon, interval of initiation rates) under which the antioxidant concentration and reactivity can be determined most reliably. The chemiluminescence method is used to study natural antioxidants in sunflower and corn oil.     

Charged and neutral particle multiplicity in π−p and π−n interactions at 40 GeV/c

Data on the multiplicity of charged particles and π⁰ mesons in π^?p and π^?n interactions are presented and compared to various models. The average π⁰ multiplicity tends to increase with increasing number of charged particles.     

Quantum-chemical investigation of some oligomeric heteroaromatic compounds

The results of calculations by the Pariser-Parr-Pople method and the expanded Hückel method of oligomeric compounds and fragments from which aromatic polyimide macromolecules are constructed are presented and discussed. In connection with the controversial character of the problem of the structures of the intermediates in the destruction of polyimides and the use, in this case, of the concept of imide-isoimide rearrangement, the relative advantageousness of the tautomeric forms of imides is evaluated, the participation of the imide ring in one or another form in conjugation is discussed, the spectral differences in the forms are established, etc. The strength characteristics of the bonds in polyimides were estimated in connection with the possibility of homolytic and hydrolytic cleavage of polyimides at these bonds.See [1] for communication II.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No.8, pp. 1048–1056, August, 1972.