Enthalpies of formation of 3,4- and 3,5-dinitro-1-trimethyl-1<Emphasis Type="Italic">Н</Emphasis>-pyrazoles

The standard enthalpies of combustion and formation for isomeric polynitropyrazoles, viz., 3,4- and 3,5-dinitro-1-trinitromethyl-1Н-pyrazoles, were measured by combustion calorimetry in an oxygen atmosphere. The enthalpies of formation for the 3,4-dinitro isomer by 19.7 kJ mol^–1 exceeds the corresponding parameter for the 3,5-isomer.     

Synthesis and van Alphen–Hüttel rearrangement of substituted 3<Emphasis Type="Italic">H</Emphasis>-pyrazoles,adducts of 1,3-dipolar cycloaddition of 9-diazofluorene and diphenyldiazomethane to trimethyl(tosylethynyl)silane

Trimethyl(tosylethynyl)silane reacted in ethyl ether at 20°С with diphenyldiazomethane affording 3Н-pyrazole, a product of 1,3-dipolar cycloaddition against Auwers rule. The reaction with 9-diazofluorene is less selective, but its regioselectivity is also governed by the steric effect of the bulky trimethylsilyl substituent at the triple bond С≡С. The adduct with diphenyldiazomethane at boiling in methanol or keeping in glacial acetic acid in the presence of a catalytic quantity of conc. H₂SO₄ undergoes the Van Alphen–Hüttel rearrangement by the migration of the phenyl substituent to the atom N² in the 1Н-pyrazole. The same 1Н-pyrazole together with a product of nitrogen elimination, trimethylsilyl substituted cyclopropane, is formed in the 2: 1 ratio at boiling in benzene. A similar behavior is observed in the glacial acetic acid for the anti-Auwers adduct of 9-diazofluorene. It suffers nitrogen elimination at boiling in benzene converting in spirocyclic cyclopropene. The Auwers adduct of 9-diazofluorene at boiling in methanol transforms due to the van Alphen–Hüttel rearrangement into the corresponding 4Н-pyrazole that undergoes a hydrodesilylation to give a derivative of 1Н-pyrazole, 3-tosyl-1(2)H-dibenzo[e,g]indazole.     

Thermochemical analysis of intermolecular interactions between <Emphasis Type="Italic">N</Emphasis>-acetylglycine and polyols in aqueous solutions

The integral enthalpies of dissolution Δ_sol H _m for N-acetylglycine in aqueous solutions of glycerol, ethylene glycol and 1,2-propylene glycol are measured via solution calorimetry. The standard enthalpies of dissolution (Δ_sol Н ⁰) and transfer (Δ_tr Н ⁰) for N-acetylglycine from water to aqueous solutions of polyhydric alcohols are calculated from experimental data. Positive values of enthalpy coefficients of pair interactions h _xy for amino acids and polyol molecules are calculated using the McMillan–Mayer theory. The results are discussed using an approach for evaluating different types of interactions in ternary systems and the effect the structural features of interacting biomolecules have on the thermochemical characteristics of N-acetylglycine dissolution.     

Thermodynamics of hexadecyltrimethylammonium bromide micelle formation

The thermodynamic parameters for CTAB micelle formation (ΔН, ΔG, ΔS) are calculated at different temperatures. Critical micelle concentrations CMC1 are determined. The possibility of determining CMC2 is demonstrated.     

Dehydrogenation of 1-aryl(hetaryl)-1,2,3,4-tetrahydro-9<Emphasis Type="Italic">H</Emphasis>-β-carboline-3-carboxylic acids and their esters with dimethyl sulfoxide

Oxidative dehydrogenation of 1-aryl(hetaryl)-1,2,3,4-tetrahydro-9Н-β-carboline-3-carboxylic acids derivatives with dimethyl sulfoxide leads to the formation of 1-aryl(hetaryl)-9Н-β-carbolines. Simultaneously with the dehydrogenation decarboxylation occurs. At the oxidation with dimethyl sulfoxide of methyl 1-aryl (hetaryl)-1,2,3,4-tetrahydro-9Н-β-carboline-3-carboxylicates methyl 1-aryl(hetaryl)-9Н-β-carboline-3-carboxylates formed whose hydrolysis afforded the corresponding 1-aryl(hetaryl)-9Н-β-carboline-3-carboxylic acids.     

Reaction 5-(Arylmethylidene)pyrimidine-2,4,6(1<Emphasis Type="Italic">H</Emphasis>,3<Emphasis Type="Italic">H</Emphasis>,5<Emphasis Type="Italic">H</Emphasis>)-triones with L-Proline and Aldehydes

Boiling in toluene of 5-(arylmethylidene)pyrimidine-2,4,6(1H,3H,5H)-triones with L-proline and aldehyde led to the formation of previously unknown substituted 1′-arylhexahydro-1H-spiro[pyrimidine-5,2′-pyrrolysine]-2,4,6(1H,3Н,5Н)-triones.     

Rearrangements of 3<Emphasis Type="Italic">H</Emphasis>-Pyrazoles—Adducts of Dimethyl Acetylenedicarboxylate with Diphenyldiazomethane and 9-Diazofluorene

Structurally related 3H-pyrazoles resulting from 1,3-dipolar cycloaddition of diphenyldiazomethane and 9-diazofluorene to dimethyl acetylenedicarboxylate undergo van Alphen–Hüttel rearrangement on heating in a polar solvent (methanol, ethanol, acetic acid). In the first case, the rearrangement involves strictly regioselective 1,5-phenyl migration toward the carbon atom with the formation of relatively stable 4H-pyrazole. Post-rearrangement of the product on heating at 180°C in toluene gives a mixture of methyl 1H-pyrazole-1-carboxylates via successive migrations of the CO₂Me group. In the second case, the aryl substituent concurrently migrates both to nitrogen atom with the formation of 1H-pyrazole structure (phenanthridine derivative) and to carbon atom with subsequent rearrangement of unstable 4H-pyrazole to 3H-pyrazole fused to phenanthrene fragment. Heating of dimethyl acetylenedicarboxylate adducts (3H-pyrazoles) in an aprotic solvent (benzene, toluene) leads to the corresponding denitrogenation products. This process is especially facile for the spirocyclic 3H-pyrazole derived from 9-diazofluorene, and it yields cyclopropene derivative. Some previous errors in the structure determination of the rearrangement products have been corrected.     

1-Alkylpyrazoles and 1-alkyl-5-chloropyrazoles from halovinyl ketones and 1,1-dialkylhydrazines

Regioselective heterocyclization of alkyl 2-chloro-and 2,2-dichlorovinyl ketones with 1,1-dialkyl-hydrazines to 1,3-dialkyl-1H-pyrazoles and 1,3-dialkyl-5-chloro-1H-pyrazoles involves intermediate formation of the corresponding dialkylhydrazones. Fragmentation pattern of chlorine-containing pyrazoles, 3-chloromethyl-1-methyl-1H-pyrazole and 5-chloro-1-methyl-3-propyl-1H-pyrazole, depends on the position of the halogen atom.     

Oxidative Addition of <Emphasis Type="Italic">N</Emphasis>-Aminophthalimide to Alkenyl-4,5-dihydropyrazoles and Alkenylpyrazoles. Synthesis of Aziridinylpyrazoles

Oxidation of N-aminophthalimide with lead tetraacetate in the presence of 1,5-diaryl-3-[(E)-2-arylethenyl]-1H-pyrazoles, as well as of 1,3-diphenyl-5-[(E)-2-phenylethenyl]-1H-pyrazole, gives adducts at the exocyclic C=C bond, the corresponding phthalimidoaziridinylpyrazoles. From 1,5-diphenyl-3-[(1E,3E)-4-phenyl-1,3-butadienyl]-1H-pyrazole, only product of addition at both exocyclic C=C bonds was obtained. In the reaction with 1-phenyl-3-[(1E, 3E)-4-phenyl-1,3-butadienyl]-5-[(E)-2-phenylethenyl]-1H-pyrazole, the adduct at the styryl C=C bond was isolated. Analogous 4,5-dihydropyrazoles, 1,5-diphenyl-3-[(1E, 3E)-4-phenyl-1,3-butadienyl]-4,5-dihydro-1H-pyrazole and 1-phenyl-3-[(1E, 3E)-4-phenyl-1,3-butadienyl]-5-[(E)-2-phenylethenyl]-4,5-dihydro-1H-pyrazole, turned out to be inert in oxidative addition of N-aminophthalimide.     

Alkenyl derivatives of 5-nitro-2-pyridone: Synthesis and halocyclization

Alkylation of 5-nitro-2-pyridone by alkenyl halides in acetone in the presence of K₂СО₃ proceeds with generation of a mixture of N- and О-derivatives with N-isomer prevailing. 1-Allyl- and 1-methylallyl-5-nitro-2-pyridone react with halogens with the formation of 2-halomethyl-6-nitro-2,3-dihydrooxazolo[3,2-a]-pyridinium halides. 1-Prenyl-5-nitro-2-pyridone reacts with bromine with the formation of 3-bromine-2,2-dimethyl-7-nitro-3,4-dihydro-2Н-pyrido[2,1-b][1,3]oxazinium bromide, and with iodine giving 2,2-dimethyl-7-nitro-3,4-dihydro-2Н-pyrido[2,1-b][1,3]oxazinium triiodide.     

The Schiff bases of pyridoxal-5-phosphate and hydrazides of certain pyrazoles: Stability,kinetics of formation,and synthesis

The interaction of pyridoxal-5-phosphate with 3-methyl-1Н-pyrazole-5-carbohydrazide, 2-(3,5-dimethyl-1Н-pyrazol-4-yl)acetohydrazide, and 1Н-pyrazole-3-carbohydrazide has yielded Schiff bases; the products have been characterized by ¹Н NMR and IR spectra. The binding ability of these pyrazoles with respect to pyridoxal-5-phosphate under conditions modeling the living tissues has been evaluated. Rate constants of the formation of the Schiff bases have been determined.     

Fused pyrimidine systems: XVI. Electrophilic intramolecular cyclization of 2-(alkenylsulfanyl)pteridin-4(3<Emphasis Type="Italic">H</Emphasis>)-ones

2-[Allyl(but-3-en-1-yl, pent-4-en-1-yl)sulfanyl]pteridin-4(3Н)-ones at heating in polyphosphoric acid undergo an intramolecular cyclization affording respectively 9-methyl-8,9-dihydro-5H-[1,3]thiazolo[3,2-a] pteridin-5-one and 10-methyl(ethyl)-9,10-dihydro-5Н,8Н-[1,3]thiazino[3,2-a]pteridin-5-ones of angular structure. The cyclization of 2-(alkenylsulfanyl)pteridin-4(3Н)-ones under the action of iodine or arylsulfenyl chlorides afforded iodo(arylsulfanyl) derivatives of angularly fuzed thiazolo- and thiazinopteridines.     

Oxidation of reaction products of <Emphasis Type="Italic">p</Emphasis>-aryl-<Emphasis Type="Italic">С</Emphasis>,<Emphasis Type="Italic">С</Emphasis>-disubstituted nitrones and dimethyl 3-methylenecyclopropane-1,2-dicarboxylate

Oxidation with 2,3-dichloro-4,5-dicyanobenzoquinone of 2,4-dihydro-1Н-azeto[1,2-a]quinoline-3,4 -dicarboxylates obtained in the reaction of N-aryl-С,С-disubstituted nitrones with Feist’s acid ester resulted in the formation of 2-vinylquinoline-3,4-dicarboxylates in good yields.     

Interaction of 1,5,6,8-tetrahydropyrazolo[3,4-<Emphasis Type="Italic">е</Emphasis>][1,4]diazepine-4,7-diones with some electrophilic reagents

1,5,6,8-Tetrahydropyrazolo[3,4-e][1,4]diazepine-4,7-diones undergo acylation with acetic anhydride and carbamoylation with p-toluensulfonyl isocyanate at the atom N⁵. Interaction with Vilsmeier- Haack reagent occurs at the atom N⁸, it is followed with the opening of the diazepine cycle and leads to the formation of 2-(1Н-pyrazol-4-yl)-1,3-oxazol-5(4Н)-one derivatives.     

Nitro derivatives of 1,3-dihydrobenzimidazol-2-one: I. Synthesis of <Emphasis Type="Italic">N</Emphasis>-nitrobenzimidazol-2-ones

1,3,5,6-Tetranitro-2,3-dihydro-1H-benzimidazol-2-one, 1,5,6-trinitro-2,3-dihydro-1H-benzimidazol-2-one, and 1,4,5,6-tetranitro-2,3-dihydro-1H-benzimidazol-2-one were synthesized for the first time by nitration of 5,6-di- and 4,5,6-trinitro-2,3-dihydro-1H-benzimidazol-2-ones with concentrated nitric acid in acetic anhydride.     

Spatial Structure of Tetrasubstituted Thiacalix[4]arenes Containing L-Tryptophan Fragments in Solution

The steric structure of the cone and 1,3-alternate stereoisomers of p-tert-butylthiacalix[4]arenes bearing in the lower rim four substituents containing amide and ammonium groups as well as L-tryptophan residues was studied by ¹Н, ¹³С, ¹Н–¹Н NOESY, and ¹Н–¹³С HSQC NMR spectroscopy. The mutual repulsion of the charged ammonium groups and the presence of intramolecular hydrogen bonds in the synthesized compounds can make the peptide bond with the tryptophan residue sterically accessible for enzymes.     

Synthesis and thermal conversions of unsaturated nickel(II) dicarboxylates as precursors of metallopolymer nanocomposites

Nickel(II) dicarboxylates of unsaturated carboxylic acids (maleic (MalA), itaconic (ItA), acetylenedicarboxylic (ADCA), allylmalonic (AlMalA), glutaconic (GlutA), cis,cis-muconic (MucA) acids) were synthesized and characterized by thermal analysis and IR spectroscopy. The synthesized dicarboxylates were subjected to thermolysis, and the obtained nanocomposites were studied by transmission and scanning electron microscopy and X-ray diffraction. The synthesized metallopolymer nanocomposites were NiO and metallic Ni nanoparticles distributed over a stabilizing matrix. The formation enthalpy of dicarboxylates (ΔН_r^°) was calculated by the PM3 semi-empirical quantum-chemical method. The nanoparticle size was determined, and a relationship between the average nanoparticle diameter (d_avg) and ΔН_r^° was established. The microstructure and magnetic characteristics of the obtained nanocomposites, namely, the maximum and residual magnetization and the coercive force, were studied.     

<Emphasis Type="Italic">N</Emphasis>-acylimino-substituted 2-oxa-7-azaspiro[4.4]nona-3,6,8-trienes in the synthesis of 3-(1<Emphasis Type="Italic">H</Emphasis>-1,2,4-triazol-3-yl)-3<Emphasis Type="Italic">H</Emphasis>-pyrrole-4-carbonitriles

Reaction with phenylhydrazine of 3Н-pyrroles spirobound to a furan ring, N-acylimino-substituted 2-oxa-7-azaspiro[4.4]nona-3,6,8-trienes, occurs with a diasteroselective formation of previously unknown derivatives of 1,2,4-triazole: 5-amino-3-(5-alkyl-1-phenyl-1H-1,2,4-triazol-3-yl)-2-morpholin-4-yl-3H-pyrrole-4-carbonitriles.     

Cyclizations of monocyclic 5-nitropyridin-2(1<Emphasis Type="Italic">H</Emphasis>)-ones

Reactions of 5-nitropyridin-2(1H)-one and its N-methyl derivative with hydrazine hydrate led to the formation of (1H-pyrazol-3-yl) acetohydrazide. Under analogous conditions, 1,3-dimethyl-5-nitropyridin2(1H)-one gave rise to 2-(1H-pyrazol-3-yl)propionohydrazide, while 6-methyl-5-nitropyridin-2(1H)-one was converted into (5-methyl-1H-pyrazol-3-yl)acetohydrazide. Hydrazinolysis of 4-methyl-5-nitropyridin-2(1H)-one resulted in the formation of 3-methyl-4-nitro-1H-pyrazole. The mechanism of recyclization of nitropyridine derivatives by the action of hydrazine hydrate was studied using 5-nitropyridin-2(1H)-one and 1-methyl-5-nitropyridin-2(1H)-one as examples.     

Reaction of S-allyl and propargyl derivatives of 2-thiouracils with hydrobromic acid

Hydrobromic acid reacts with 2-methallylthio- and 2-prenylthio-4(3Н)-pyrimidinones with participation of the double bond to give the products of heterocyclization, and with 2-allylthio- and 2-propargylthio-6-methyl-4(3Н)-pyrimidinones, with the retention of the double bond and the formation of hydrobromides.