Reaction of aroyl- and hetaroyltrifluoroacetones with acylhydrazines: Regioselectivity and tautomerism of the condensation products

Acylhydrazines react with 1,3-diketones of the general formula CF₃COCH₂COR (where R is an aryl or hetaryl group) at both carbonyl groups. The reaction at the trifluoroacetyl group is favored by donor substituents in the aromatic ring of the 1,3-diketone or by the 2-furyl and, especially, 2-thienyl group as a hetaryl substituent, as well as by elevated temperature. The condensation products at the carbonyl group contiguous to the aryl or hetaryl ring have the structure of 5-hydroxy-4,5-dihydropyrazoles and do not undergo tautomeric transformations in solution. The condensation products at the trifluoroacetyl group have either 5-hydroxy-4,5-dihydropyrazole or hydrazone structure and give rise to ring-chain tautomeric equilibrium in solution. Electron-withdrawing substituents in the aromatic ring of the 1,3-dicarbonyl fragment and CDCl₃ as solvent favor formation of the cyclic tautomer. The state of the tautomeric equilibrium is weakly sensitive to structural variations in the hydrazine component.     

Anisotropy of cubic semimagnetic Cd1−x MnxTe solid solutions and excitonic magnetic polaron energy from polarized-luminescence measurements

Polarized photoluminescence of Cd_1−x Mn_xTe crystals in a weak magnetic field has been studied in Faraday and Voigt geometries. A simple method is proposed to determine the exciton mobility edge and excitonic magnetic-polaron energy. “Forbidden” polarization components of the recombination radiation have been experimentally detected. It has been established that the moments of magnetic polarons are oriented predominantly along the {111} axes. Fiz. Tverd. Tela (St. Petersburg) 40, 894–896 (May 1998)     

Systems for the suppression of spectral interferences for inductively coupled plasma mass-spectrometry

This review considers the basics, principles of operation and practical application of spectral interference suppression systems based on multipole gas-filled cells.     

Mn<Superscript>2+</Superscript> 3<Emphasis Type="Italic">d</Emphasis> luminescence kinetics in Zn<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Mn<Subscript>x</Subscript>Se

Intracenter luminescence (IL) of Mn²⁺ in Zn_1?xMn_xSe (x=0.07, 0.02) was studied under pulsed excitation by the neodymium laser second harmonic. At 4 K, the IL saturation originates from the nonlinearity of the system only at the instant of excitation, the IL decay kinetics after the exciting pulse termination depending only weakly on the pumping level. At 77 K, the decay kinetics in Zn_0.93Mn_0.07Se depends substantially on the pumping level, because the migration of intracenter excitation over the manganese ions initiates up-conversion, which is a slow nonlinear process. As shown by IL decay measurements in Zn_0.98Mn_0.02Se (x=0.02), excitation migration over the Mn²⁺ ions is insignificant even at a high temperature and under strong optical pumping.     

Structure of aldose condensation products with 2-hydroxyand 2-sulfanylbenzohydrazides

The structure of the condensation products of 2-hydroxy- and 2-sulfanylbenzohydrazides with a series of aldoses (L-arabinose, D-ribose, L-ramnose, D-galactose, D-glucose, D-mannose) was studied by ¹H and ¹³C NMR spectroscopy. The condensation products of monosaccharides with 2-hydroxybenzohydrazide in DMSO-d ₆ solution exist as equilibrium mixtures of linear hydrazone and cyclic pyranose and furanose forms, the cyclic tautomers being represented by two stereoisomers (α- and β-anomers). The aldose condensation products with 2-sulfanylbenzohydrazide in the crystalline state have cyclic 1,3,4-benzothiadiazepine structure, while in DMSO-d ₆ solution they undergo complete or partial isomerization into cyclic pyranose tautomer.     

Reactions of tri- and hexafluoroacetylacetones and 4-ethoxy-1,1,1-trifluorobut-3-en-2-one with 2-aminobenzohydrazide

Reactions of 1,1,1-trifluoropentane-2,4-dione and 1,1,1,5,5,5-hexafluoropentane-2,4-dione with 2-aminobenzohydrazide afforded (2-aminophenyl)[5-hydroxy-3-methyl-5-(trifluoromethyl)- and (2-aminophenyl)[ 5-hydroxy-3,5-bis(trifluoromethyl)-4,5-dihydropyrazol-1-yl]methanones, respectively. 4-Ethoxy-1,1,1- trifluorobut-3-en-2-one reacted with 2-aminobenzhydrazide to give 2-(trifluoromethyl)-3a,4-dihydropyrazolo-[5,1-{ptb}]quinazolin-9(3{ptH})-one.     

An investigation in the field of the stereochemistry of acetylenic α oxides

In the synthesis of 3-methyl-2,3-epoxypent-4-yne by the action of powdered caustic potash on 4-chloro-3-methylpent-1-yn-3-ol, a mixture of cis and trans oxides is formed with predominance of the isomer to which, on the basis of the PMR spectroscopy of saturated and acetylenic -oxides, the cis configuration of the methyl groups has been ascribed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 19–21, January, 1974.