Highly regioselective synthesis of trifluoromethyl derivatives of pyrazolo[1,5-a]pyrimidines bearing fused cycloalkane rings using (2-ethoxycycloalkenyl)-2,2,2-trifluoroethanones

8-Trifluoromethyl-6,7-dihydro-5H-1,4,8a-triaza-s-indacene and 9-trifluoromethyl-5,6,7,8-tetrahydropyrazolo[5,1-b]quinazolines were efficiently generated by condensation of 5(3)-aminopyrazoles with (2-ethoxycycloalkenyl)-2,2,2-trifluoroethanones and isolated in excellent yields. The regiochemistry of the prepared compounds was established by ¹H, ¹³C and ¹⁹F NMR spectroscopy and X-ray diffraction analysis.     

α-aminoazoles in the Synthesis of heterocycles: V. Synthesis of azolo[1,5-a]pyrimidines from 2-ethoxyvinyl trifluoromethyl ketones and 2,2-diethoxyvinyl trifluoromethyl ketone

A procedure was proposed for the synthesis of 7-trifluoromethylazolo[1,5-a]pyrimidines by reactions of 2-ethoxyvinyl trifluoromethyl ketones and 2,2-diethoxyvinyl trifluoromethyl ketone with 5(3)-aminoazoles. The reactions occurred under mild conditions, and the products were formed with high yield and regioselectivity.     

Study of regioselectivity of reactions between 3(5)-aminopyrazoles and 2-acetylcycloalkanones

Regioselectivity was examined of reactions between nine 3(5)-aminopyrazoles and 2-acetylcyclopentanone and 2-acetylcyclohexanone under various conditions. A series of cyclopenta[e]pyrazolo-[1,5-a]pyrimidines was obtained. The highest regioselectivity of the reaction was observed in alcohol at 20°C in the presence of a catalytic quantity of trifl uoroacetic acid. The regiostructure of compounds was established by ¹H and ¹³C NMR spectroscopy.     

α-Amino azoles in the synthesis of heterocycles: VI. Synthesis and structure of cycloalkane-annulated pyrazolo[1,5-<Emphasis Type="Italic">a</Emphasis>]pyrimidines

Reactions of 4-aryl-1H-pyrazol-5(3)-amines with 2-acylcycloakanones and 2-acyl-5,5-dimethylcyclohexane-1,3-diones led to the formation of regioisomeric 6,7,8,9-tetrahydropyrazolo[1,5-a]quinazoline, 5,6,7,8-tetrahydropyrazolo[5,1-b]quinazoline, and 7,8-dihydro-6H-cyclopenta[e]pyrazolo[1,5-a]pyrimidine derivatives. The product structure was determined by X-ray analysis and ¹H and ¹³C NMR spectroscopy.     

Analysis of Atmospheric Aerosols by Atomic Emission Spectrometry with Electrical Discharge Sampling

A procedure has been developed for the determination of the concentration of heavy metals (Pb, Mn, Cu, Ni, Zn, and Cd) in atmospheric air by atomic emission spectrometry with gas-discharge sampling onto the end of a standard carbon electrode. A design of a two-section sampler is proposed; the sampler provides the rapid determination of deposition factors for heavy metals contained in aerosol particles deposited onto the end of a carbon electrode. Examples of determining metal concentrations in a model sample of air and in atmospheric air and determination limits of metals deposited onto the end of a carbon electrode are given.     

The formation of nalidixic acid dimers and excimers in aqueous solutions

The influence of optical excitation on the formation of nalidixic acid dimers and excimers in aqueous media in the ground and excited states was studied. Quantum-chemical calculations of the total energy of monomers and dimers were performed. The spectral-luminescent characteristics of pairs of nlqH molecules were measured, and changes in charges on atoms in the ground and excited states were estimated.     

α-aminoazoles in synthesis of heterocycles: IV. Regiodirection of 3(5)-amino-5(3)-methylpyrazole reaction with hexafluoroacetylacetone

The reaction of 3(5)-amino-5(3)-methylpyrazole with hexafluoroacetylacetone depending on the process conditions led to the formation either of pyrazolo[1,5-a]pyrimidine or pyrazolo[3,4-b]-pyridine. By means of 2D NMR spectroscopy the structure was established of a stable intermediate product, 2-methyl-5,7-bis(trifluoromethyl)-4,5,6,7-tetrahydropyrazolo[1,5-a]-pyrimidine-5,7-diol, whose dehydration yielded the above compounds.