Synthesis of aromatic pyrazolo[4,5-b]pyridine derivatives

Cyclocondensation of chalcones with 5-amino-3-methyl-1-phenylpyrazole leads to the formation of 2,4-diaryl-5-methyl-7-phenyl-3,4-dihydropyrazolo-[4,5-b]pyridines, which undergo aromatization upon treatment with N-bromosuccinimide.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1247–1251, September, 1987.     

Metrical diophantine approximation for continued fraction like maps of the interval

We study the metrical properties of a class of continued fraction-like mappings of the unit interval, each of which is defined as the fractional part of a Möbius transformation taking the endpoints of the interval to zero and infinity.

     

Extraction of kinetic freeze-out properties and effect of resonance decays

We present STAR results from identified particle spectra measured in $\sqrt {s_{NN} } = 62.4$ GEV Au-Au collisions. Particle production and system dynamics are compared to results at $\sqrt {s_{NN} } = 200$ GeV. We extract kinetic and chemical freeze-out parameters using blast wave model parametrization and statistical model. We discuss the effect of resonance decays on the extracted kinetic freeze-out parameters.     

Metal dilution effects on the spin-crossover properties of the three-dimensional coordination polymer Fe(pyrazine)[Pt(CN)4

The 1A1 left arrow over right arrow 5T2 spin transition has been investigated in the solid solutions of Fe(x)M(1-x)(pyrazine)[Pt(CN)4] (M = Ni or Co, 0 < or = x < or = 1) having a three-dimensional polynuclear structure. Both Ni and Co dilutions tend to decrease the hysteresis width and smooth the transition curves. The enthalpy (entropy) change associated with the spin transition was found to decrease from 26 kJ mol(-1) (84 J K(-1) mol(-1)) for x = 1 to 12 kJ mol(-1) (47 J K(-1) mol(-1)) for 47% Co dilution and to 15 kJ mol(-1) (54 J K(-1) mol(-1)) for 59% Ni dilution. Raman spectroscopy revealed a mixed one- and two-mode behavior in the solid solutions. For the first time, a correlation between vibrational frequencies exhibiting one-mode behavior and the entropy change, which drives the spin crossover, is established.     

Reactions of 4,5-diaminopyrazoles with chalcones and acetylarenes

Reaction of 3-methyl-1-(4-nitrophenyl)-4,5-diaminopyrazole with chalcones and acetylarenes gave 1H-2,3-dihydropyrazolo[4,5-b]-1,5-diazepines. The structure of one of these was confirmed by x-ray analysis. 3,5-Diphenyl- and 3-oxo-4,5-diaminopyrazoles did not take part in this reaction.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 506–510, April, 1992.     

Carbon tether rigidity as a stereochemical tool directing intramolecular radical cyclizations

The phenyl group incorporated into a carbon tether provides for the synthesis of 1,5-cyclodecadiynes with 95-100% d,l-diastereoselectivity due to intrinsic conformational constraints and preorganization of the Co₂(CO)₆-complexed propargyl intermediates.     

IR Transmittance of Si/SiO2/Si3N4/Si Insular Structures Formed by Selective Laser Annealing

Journal of Applied Spectroscopy - Periodic Si/SiO2/Si3N4/Si structures with an insular surface layer were formed by selective laser annealing. A study by Fourier infrared spectrometry in the range...