Nitroazines. 19. Prototropic tautomerism in 6-nitro-7-oxo-4,7-dihydro-1,2,4-triazolo[5,1-c][1,2,4]triazines

Prototropic reactions of 6-nitro-7-oxo-4,7-dihydro-1,2,4-triazolo[5,1-c][1,2,4]triazines is tautomeric as established from photoionization results. The ratios of the tautomers in the gas phase and in solution have been determined by mass and ¹³C NMR spectroscopy.For Communication 18 see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1555–1559, November, 1992.     

Maps of intragranular precipitation strengthening

Maps of strengthening by small (semi)coherent precipitates homogeneously dispersed in the grains have been constructed. They can show the most probable dislocation-particle interaction mechanism and the strengthening effect of a given dispersion of particles. As an application, the effect of-Ni₃(Al, Ti) and M₂₃C₆ precipitation in austenitic steels is discussed.     

Cyclocondensation of 2-Aminobenzimidazole with Dimedone and Its Arylidene Derivatives

The reactions of 2-aminobenzimidazole with substituted benzaldehydes and dimedone, 2-arylidene derivatives of dimedone, 9-arylhexahydro-1H-xanthene-1,8(2H)-diones and also with dimedone and DMF have been studied. The direction of formation of the pyrimidine ring has been established and discussed. An X-ray structural investigation of 2,2-dimethyl-2,3-dihydrobenzimidazo[1,2-a]quinazolin-4(1H)-one has been carried out.     

Infrared absorption and electron paramagnetic resonance studies of vinyl radical in noble-gas matrices

Vinyl radicals produced by annealing-induced reaction of mobilized hydrogen atoms with acetylene molecules in solid noble-gas matrices (Ar, Kr, and Xe) were characterized by Fourier transform infrared and electron paramagnetic resonance (EPR) spectroscopies. The hydrogen atoms were generated from acetylene by UV photolysis or fast electron irradiation. Two vibrational modes of the vinyl radical (nu7 and nu5) were assigned in IR absorption studies. The assignment is based on data for various isotopic substitutions (D and 13C) and confirmed by comparison with the EPR measurements and density-functional theory calculations. The data on the nu7 mode is in agreement with previous experimental and theoretical results whereas the nu5 frequency agrees well with the computational data but conflicts with the gas-phase IR emission results.     

Kinetic equations with a complex balanced stationary point

A class of ordinary differential equations including nonideal nonisothermal kinetics is introduced. The behavior of their solutions for the system with a positive complex-balanced stationary point is studied. Sufficient conditions for this point to exist are described.

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Electrophilic substitution in n-aryl-2-pyrazolines: Reactions with 1,3-dithioles

Dyes that absorb at 525–580 nm were obtained by the reaction of derivatives of 1,3-dithiolium iodide (or perchlorate) with 1-phenyl-3,5-di-R-2-pyrazolines, N,N-dimethylaniline, and benzaldehyde N-methylphenylhydrazone. It was demonstrated by alternative synthesis that the reaction takes place in the para position of the N-phenyl group. Dyes can be obtained in two steps from 2-dimethylamino-1,3-dithioles and activated aromatic compounds with subsequent oxidation of the intermediate leuco compounds with air oxygen.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1245–1250, September, 1981.     

Reaction of 1,2-Diamino-4,5-diphenylimidazole with 1,3-Diarylpropenones and Their Dibromo Derivatives

The reaction of 1,2-diamino-4,5-diphenylimidazole with 1,3-diarylpropenones and 1,3-diaryl-2,3-dibromopropenones gives dihydro- and heteroaromatic derivatives of 6-hydroxyimidazopyrimidines and also imidazopyrimidines which do not contain the 6-hydroxy group. It was found that the structure of the products depended on the conditions for carrying it the reaction.     

Conformational analysis of 5,6-dihydropyrimidine and its derivatives

The equilibrium geometry and inversion barriers of 5,6-dihydropyrimidine, 6,7-dihydroazolopyrimidines with node nitrogen atoms and their alkyl (Me, Et, Prⁱ, Bu^t) and phenyl derivatives were calculated using a molecular mechanics approach. Annelation with azole cycles and the introduction of substituents have a slight effect on the equilibrium conformation of the dihydrocycle (distorted sofa). Alkyl substutuents at saturated carbons have an essentially equatorial orientation in 5,6-dihydropyridimine derivatives and are axial in the annelated analogs. On the other hand, the equatorial conformers are more stable in phenyl derivatives of dihydroazolopyrimidines. Factors determining the relative stability of conformers were analyzed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 487–491, March, 1995.     

Oxidation of 1-aminobenzimidazoles. Synthesis and properties of 1,1′-azobenzimidazoles

1-Amino-2-R-benzimidazoles are oxidized by lead tetraacetate to give, depending on the substituent in the 2-position, either to 1,1-azobenzimidazoles (R=H, CH₃, C₆H₅, Cl, N(CH₃)₂) or 3-R-benzo-1,2,4-triazines (R=NH₂, NHCH₃, NHC₆H₅, OH). The factors affecting the course of the reaction are discussed. The physicochemical properties of the 1,1-azobenzimidiazoles obtained have been examined.For preliminary communication, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1486–1499, November, 1989.