Catalysts for enantioselective Biginelli reaction based on the composite silica-zirconia xerogels prepared using different zirconium sources

The composite silica-zirconia xerogels have been prepared via sol–gel method using zirconium oxychloride, oxynitrate, acetate and sodium silicate as the precursors. The prepared materials have been characterized using FTIR, TG/DTA, EDX and surface area analyses. It has been established that surface area of silica-zirconia xerogels significantly depends on the zirconium source, but phase transitions and structural features of the xerogels seem to be unaffected by the choice of the zirconia precursor. Prepared xerogels increase the activity of chiral inductor in the asymmetric Biginelli reaction. The anion of the zirconium salt adsorbed on the surface of the synthesized material and the presence of Si–O–Zr heterolinkages determines the reaction yield. The highest chemo- and enantioselectivity towards formation of ee isomer have been provided by the catalyst prepared from zirconium oxychloride.     

Signal dynamics of the photothermal response in three-level media

In this paper, we consider the process of optical recording and decay of transient spatial structures in a system with a nonlinear response caused by incoherent saturation of three-level centers. The main attention is devoted to the thermal mechanism of phase recording in media with a temperature-independent heat conductivity. The relaxation of an inhomogeneous temperature field and the diffraction of a probe beam from the transient structure are studied. The designed theoretical model satisfactorily describes the obtained experimental results and allows the evolution of a temperature field to be viewed.     

tert-Butyldiazene oxide as a leaving group

Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, p. 995, July, 1990.     

Reaction of ethyl 9-thioacridonyl-10-acetate with hydrazine

The reaction of ethyl 9-thioacridonyl-10-acetate with hydrazine hydrate gives the corresponding ethyl hydrazonoacridonyl-10-acetate, which readily undergoes a reaction with aldehydes and on heating in DMF reacts with hydrazine hydrate to form 9-ylidenehydrazonoacridonyl-10-acetic acid hydrazide. The latter undergoes a condensation reaction with aldehydes to form ylidenehydrazides of acridonyl-10-acetic acid 9-ylidenehydrazones. The structures of these compounds have been confirmed by UV, IR, PMR, and mass spectrometry.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 525–527, April, 1989.     

A new approach to the synthesis of lamotrigine and other 3,5-diamino-1,2,4-triazine derivatives

A new in principle method for the synthesis of 6-aryl(hetaryl)-3,5-diamino-1,2,4-triazines by decomposition of pre-synthesized tetrazolo[1,5-b][1,2,4]triazines was developed. The advantages of this method over traditional methods were demonstrated using the synthesis of a modern antiepileptic preparation lamotrigine, as an example.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 713–719, March, 2005.     

Synthesis and study of the covalent solvation of 6-nitroazalopyrimidines

The corresponding 6-nitroazolo[1,5-a]pyrimidines were obtained by the reaction of the sodium salt of nitromalondialdehyde with 3(5)-aminotriazoles and 3(5)-aminopyrazoles. The covalent solvation of the synthesized compounds was investigated by PMR spectroscopy.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1554–1556, November, 1981.     

Investigation of the thermolysis of 5-methyl-1-phenyltetrazole by combined derivatography and mass spectrometry

The thermolysis of 5-methyl-1-phenyltetrazole was studied at 20–350°C by derivatography and mass spectrometry, and it was shown that thermal decomposition proceeds with the elimination of a molecule of nitrogen and is accompanied by skeletal rearrangement of the intermediately formed nitrene to 2-methylbenzimidazole or migration of the methyl group to the nitrogen atom with the formation of methylphenylcarbodiimide (MPCD). In addition, symmetrical dimethyl- and diphenylcarbodiimides, methylphenylguanidines, and aniline are formed. It is assumed that the formation of these compounds in the pyrolyzate is due to polymerization of MPCD and subsequent thermal destruction of the polymerization products. A scheme for the thermolysis of 5-methyl-1-phenyltetrazole is proposed. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 265–271, February, 1980.