Asymmetric hydrogenation of methyl (<Emphasis Type="Italic">Z</Emphasis>)-2-acetamido-3-(3,4-dimethoxyphenyl)acrylate catalyzed by Rh complexes with available amidophosphite ligands

A convenient express procedure for the preparation of methyl (Z)-2-acetamido-3-(3,4-dimethoxyphenyl)acrylate was developed. Asymmetric hydrogenation of this substrate in the presence of rhodium catalysts involving synthetically available amidophosphite ligands was carried out, which is characterized by high enantioselectivity (to 99.5% ee) and complete conversion. An approach to the selective formation of cationic complexes containing two ligands of different nature in one coordination sphere of rhodium was suggested.     

Topological Transformations in the Acoustic Spectrum of Anisotropic Plate under Asymmetric Perturbations

It is shown how small variations in the conditions for the propagation of waveguide acoustic modes in anisotropic plates lead to a topological transformation of the entire net of acoustic dispersion curves. When both the sagittal plane and midplane of a plate are simultaneously planes of symmetry, the acoustic dispersion curves of the plate form four independent sets with many intersection points. If the symmetry is violated as a result of perturbations, the intersection points disappear and the curves are “repulsed”; thus, the eigenmode spectrum of the plate radically changes its topology. Versions of such changes are revealed. The polarization of waves in the repulsion zones sharply changes at small segments of the corresponding dispersion branches. The field structure of the wave is analyzed for the case where the perturbation is elastic anisotropy or a piezoelectric effect. The features of transformations of the acoustic spectrum of anisotropic plates in all purely elastic and piezoelectric symmetry classes are analyzed.     

Asymmetric metal complex hydrogenation of 1-methyl-3,4-dihydroisoquinoline in the presence of amidophosphite ligand

A number of metal complex precatalysts, solvents, and additives were examined in the asymmetric hydrogenation of 1-methyl-3,4-dihydroisoquinoline in the presence of a chiral amidophosphite ligand. The enantioselectivity of hydrogenation of this substrate increased upon addition of iodine. The best result in the selective hydrogenation was observed when [Ir(COD)₂]BARF was used as the precatalyst (COD is the cycloocta-1,5-diene, BARF is the tetrakis[3,5-bis(trifluoromethyl)phenyl]borate).     

Changes in the product composition during the detonation of an unconfined volume of a combustible mixture

For a model problem the solution to which describes the main features of changes in the parameters of the medium in the detonation of an unconfined gas mixture charge of in the air, direct numerical simulation, without of simplifying assumptions on changes in the composition of the mixture, was performed to study changes in the composition of the detonation products, determine the limits of applicability of the chemical equilibrium mixture model, and verify a previously obtained sufficient condition of applicability of the chemical equilibrium mixture model. The results of determining the limits of applicability of the chemical equilibrium mixture model previously obtained using an approximate method were confirmed.     

The use of an ionic liquid in asymmetric catalytic allylic amination

Asymmetric amination of 1,3-diphenyl-2-propenyl acetate with di-n-propylamine catalysed by palladium/P^∗-chiral diamidophosphites was carried out in ionic liquid, THF and CH₂Cl₂ with up to 90% ee. The catalyst can be reused three times without loss in enantioselectivity.     

Calculation of distribution functions for two-component rigid-sphere molecules of a fluid

Analytical expressions are derived and a computational algorithm and program for calculating distribution functions of rigid spheres g _ij (r) necessary for calculations of the thermodynamic parameters of a binary fluid mixture are developed in the context of perturbation theory using the procedure based on the inversion of the Laplace transform for functions rg _ij (r) obtained from the Percus–Yevick equation.     

Experimental investigation of the shape of a heavy-current air discharge without blowing

The results of investigating experimentally the shape of an are discharge burning between two electrodes in air at atmospheric pressure in the absence of blowing when the currents are less than 100 A are reported. In certain experiments the distance between the electrodes was varied in order to solve special problems. The effect of the electrode material on the shape of the discharge is investigated. It is found that the electrode material does not have a qualitative effect on the shape of the discharge but can lead to a significant variation in the parameter distribution over the discharge gap. The study is a continuation of the research described in [1].     

Dynamics of the intraocular fluid: Mathematical model and its main consequences

The problem of interaction between the intraocular pressure and the hydrodynamic processes in the eye is investigated. A lumped-parameter model taking into account a wide range of physically permissible mechanisms of the inflow and outflow of intraocular fluid is proposed. In the cases of stationary and nonstationary flow regimes, the consequences of various assumptions are analyzed. The flow in the presence of an external load is considered. It is shown that the physical interpretation of measurements used in ophthalmology strongly depends on the hypotheses adopted, the choice between which needs further investigation.     

Radio-frequency Mössbauer spectra of the “easy”-plane type magnetic system (FeBO3)

The theory of formation of the RF Mössbauer spectra for the “easy”-plane type magnetics (FeBO₃) and for various types of RF field polarization is presented. Experiments using both linearly and circularly polarized external RF fields were carried out at different temperatures. At room temperature the experimental spectra for both cases are well described by switching hyperfine (hf) field model. At temperatures close to the Neel temperature (335 K), the spectra in the oscillating and rotating RF field were obtained and their forms are described by models of switching and rotating hf field, respectively.