Electrosynthesis of 3,4-diphenylhexane-3,4-diol by the propiophenone reduction in dimethylformamide

Electrosynthesis of 3,4-diphenylhexane-3,4-diol is performed by the propiophenone reduction in a 0.2 M Et₄NBr solution in dimethylformamide under the conditions of diaphragmless galvanostatic electrolysis using Pt (Cu, Ni) cathode and Mg (Zn) anode, at a current of 0.2 A and a temperature of 30°C. The process parameters are optimized, and a preparative method is developed for producing a mixture of meso/dl-isomers of the desired product in a 1/3.3 ratio with an overall yield of 76% as calculated per loaded propiophenone at its 90-% conversion.     

The role of the polarization mechanism for emission of radiation by atoms over a broad photon frequency range

This paper develops an effective method for calculating the bremsstrahlung cross section with allowance for the polarization mechanism. We calculate the cross section of bremsstrahlung produced in the scattering of electrons and positrons by H and Kr atoms. We also demonstrate the important role of polarization bremsstrahlung in the formation of the total emission spectrum over the entire frequency range. Zh. éksp. Teor. Fiz. 114, 458–473 (August 1998)     

Photophysics of the adsorbed bipyridyl complexes of ruthenium(II) with phosphines

Luminescence of the ruthenium(II) complexes cis-Ru(bpy)₂(CN)₂ (I), cis-[Ru(bpy)₂(PPh₃)CN](BF₄) (II), and cis-Ru(bpy)(dppe)(CN)₂ (III)[bpy=2.2′-bipyridyl, PPh₃=triphenylphosphine, dppe=1,2-bis(diphenylphosphino)ethane], adsorbed on silicon oxide (Aerosil) were studied at a temperature of 77 K. The luminescence spectra, decay times, and quantum yields were measured, and the intermolecular rate constants of radiative transitions and nonradiative decay of the excited electronic state with the metal-to-ligand charge transfer (MLCT) were determined. It is found that the adsorption of the complex is accompanied by a decrease in the energy of the radiative MLCT state and by a considerable acceleration of its nonradiative decay. It is concluded that the interaction of the complexes with the surface adsorption centers occurs via formation of a strong hydrogen bond with a hydroxyl-hydrate cover, the interaction of complexes in the ³MLCT state being stronger than in the ground state. The additive (in the number of phosphorus atoms coordinated to the central ruthenium ion), a shift of the absorption and luminescence bands to shorter wavelengths in the sequence of complexes I–III, is retained when the complexes transform from solutions to the absorbed state.     

Electrocatalytic N—N cross-coupling of N-alkyl-3-aminopyrazoles at a nickel anode

Russian Chemical Bulletin -     

Electrosynthesis of 4-chloro derivatives of pyrazole and alkylpyrazoles

Electrosynthesis of 4-chloro-substituted derivatives of pyrazole and its alkyl derivatives is carried out via the chlorination of original pyrazoles on a Pt anode in aqueous NaCl solutions under conditions of galvanostatic diaphragm electrolysis. The efficiency of this process is shown to depend on the structure of starting pyrazoles, particularly, the donor-acceptor properties of substituents, the position of the latter in the pyrazole ring, and the concomitant contribution of side reactions. Thus the yield of 4-chlorosubstituted products at the chlorination of pyrazole, 3,5-dimethylpyrazole, 1,5-dimethylpyrazole, and 3-nitropyrazole is 68, 92, 53, and 79%, respectively. By the example of 1,5-dimethylpyrazole, the possibility of electrochemical chlorination to the side chain of pyrazoles was demonstrated.     

New approach to electrochemical iodination of arenes exemplified by the synthesis of 4-iodopyrazoles of different structures

The two-stage electrosynthesis of 4-iodosubstituted pyrazole derivatives was performed. At the first stage, KIO₃ was obtained at the Ni anode under the undivided galvanostatic conditions of electrolysis of an aqueous alkaline solution of KI (or I₂) at the Ni anode. At the second stage, pyrazole and its derivatives were iodinated in the heterophase (H₂O-CHCl₃ (CCl₄)) medium by the KIO₃-KI (or KIO₃-I₂) system in the presence of H₂SO₄. The yields of iodopyrazoles were 74–92%. The electrochemical iodination of anisole, 2-methylpyrazole, and thiophene was carried out to form 4-iodoanisole (88% yield), 4,5-diiodo-2-methylimidazole (54% yield), and a mixture of 2-iodothiophene (60% yield) and 2,5-diiodothiophene (4% yield).     

Dissociation and fission of small sodium and strontium clusters

Fission of charged small sodium and strontium clusters has been studied by the ab initio density functional theory methods. Dissociation energies and fission barriers have been calculated for all possible fission channels for the Na₁₀²⁺ and Sr₇²⁺ clusters. The dissociation energies and fission barriers have been analyzed as functions of the daughter fragment size.