Synthesis of new antimicrobial 4-aminosubstituted 3-nitrocoumarins

A series of new coumarin derivatives has been synthesized by condensation of 4-chloro-3-nitrocoumarin and the appropriate arylamine and sulfonamide in ethyl acetate in the presence of triethylamine. The synthesized compounds were screened for their in vitro antimicrobial activity against thirteen strains of bacteria and three fungal/yeast strains using disk diffusion assays. They were shown to possess a wide range of activities from almost completely inactive compounds to medium active ones. (4-[(5-Chloropyridin-2-yl)amino]-3-nitro-2H-chromen-2-one) showed similar activity against Klebsiella pneumoniae as tetracycline.     

Ring contraction synthesis of 2,5-disubstituted-3-arylamino-4-cyanopyrroles from 2,6-disubstituted-4-arylamino-5-cyanopyrimidines

A method for synthesis of 2,5-disubstituted-3-arylamino-4-cyanopyrroles from newly synthesised 2,6-disubstituted-4-arylamino-5-cyanopyrimidines by treatment with zinc and acetic acid, the yields being up to 80%, is developed.     

Investigations in the 4-aryl-5-arylamino-1,2,4-triazoline-3-thione series

Cyanoethylation of 4-aryl-5-arylamino-1,2,4-triazoline-3-thiones proceeds at the nitrogen atom of the thioamide group. Alkylation of 4-aryl-5-arylamino-1,2,3-triazoline-3-thiones with chloroacetonitrile, monochloroacetic acid and its ester, -chloropropionic acid, and methyl iodide proceeds at the sulfur atom. The acidity constants of substituted 4-phenyl-5-phenylamino-1,2,4-triazoline-3-thiones differ by two orders of magnitude from the acidity constants of the more acidic substituted 4-phenyl-1,2,4-triazoline-3-thiones.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 129–132, January, 1971.     

The effect of orientation of the lateral methyl substituent on the mesophase behaviour of 4-alkoxyphenylazo aryl benzoates

Two homologous series of 4-alkoxyphenylazo 4?-(2?- (and 3?-) methyl-) 4?-substituted benzoates (IIn_a–f and IIIn_a–f, six series each) were prepared and investigated. Within each series, the length of the terminal alkoxy group varies among 6, 8, 10 and 12 carbons, while the other terminal substituent, X, is a polar group that alternatively changes between the electron-donating CH₃O, CH₃, and the electron-withdrawing Br, NO₂ and CN groups, in addition to the un-substituted analogue, X = H, aiming to investigate the effect of the different orientations of the methyl groups substituted on the central benzene ring, on the mesophase behaviour. The mesomorphic properties were discussed in terms of steric and polarisability effects. The mesophase stability was correlated with the polarisability anisotropy of bonds to the terminal substituent X. Comparative studies were made between the prepared isomers with each other and with the previously investigated laterally neat analogues 4-(4?-alkoxyphenylazo) phenyl 4?-substituted benzoates (In_a–f).     

Structural effects on thermal rearrangement of fulleroids to methanofullerenes. The prominent role of cyclopropyl vs aryl substituent

The kinetics of the thermal rearrangement of a series of novel cyclopropyl-substituted [5,6] open fulleroids to the [6,6] closed methanofullerenes have been investigated in comparison with the aryl-substituted homologues. The cyclopropyl group markedly accelerated the rates due to the stereoelectronically favorable pi-conjugative effects in the radical-like [1,5] shift of the transient [5,6] closed isomers, overriding the geometrically constrained aryl group.     

Influence of aryl substituents on the thermal and solubility behavior of poly(p-phenylene terephthalate) and poly(p-phenylene terephthalamide)

The substitution of poly(p-phenylene terephthalate) and poly(p-phenylene terephthalamide) with phenyl and biphenylyl substituents (4-biphenylyl and 2-biphenylyl) in the terephthalic acid unit lowers the melting temperatures and crystallization tendency and increases the solubility. The melting temperatures of the polyesters are in the range of 285–350°C. Melting of the polyamides occurs between 440–490°C. The polyamides begin to decompose in the same temperature range. In polyesters as well as in polyamides the 2-biphenylyl substituent was found to be more effective in decreasing the crystallinity, lowering the melt transition temperatures and increasing the solubility.     

Influence of an equatorial substituent at C4 in 3-ketopiperidines on the stereochemistry of the reduction of the keto functional group

Conclusions In 3-ketopiperidines an e-methyl at C⁴ specifically shields the axial region of the carbonyl only with respect to reduction by aluminum isopropoxide and, to a lesser degree, to reduction over platinum.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2352–2356, October, 1983.     

Effect of position of the lateral fluoro substituent on the mesophase behaviour of aryl 4-alkoxyphenylazo benzoates in pure and binary mixtures

Five groups of 4-substituted phenyl 4?-(2?- (or 3″-) substituted-4?-alkoxyphenylazo) benzoates (In_a-c to Vn_a-c) were investigated in which, within each group, the length of the terminal alkoxy group varies between 8 and 16 carbons, while the other terminal substituent, X, is a polar group that alternatively changed between the electron-donating CH₃O and the electron-withdrawing Br group, in addition to the un-substituted analogue (X = H). The lateral substituent (Y) in the five groups I–V varies, respectively, between H, 3-CH₃, 2-CH₃, 3-F and 2-F. Their mesophase stabilities were determined by differential scanning calorimetry and phases identified by polarised light microscopy. The two newly prepared groups of compounds (IVn_a-c and Vn_a-c) are structurally characterised by infrared, ¹H-NMR, mass spectroscopy, thermogravimetric and elemental analyses. Binary phase diagrams were constructed for each pair of isomers from groups IV and V bearing the same wing substituents but the lateral F is attached to different positions (2? or 3″).     

Evaluation of substituent effects on activity and enantioselectivity in the enzymatic reduction of aryl ketones

The enzymatic reduction of a series of substituted aryl ketones catalyzed by 24 isolated recombinant ketoreductases was studied and the substituent effects on activity and enantioselectivity were evaluated. When comparing p- and m-substituted acetophenones, the substituent significantly affects the activity of some of the tested ketoreductases, while it has little effect on the activity of other ketoreductases. Most of the tested ketoreductases were highly enantioselective in the reduction of these aryl ketones. The electronic properties, steric factors, and the ability to form a hydrogen bond to the substituents at the ortho-position play a significant role in determining both the activity and enantioselectivity of the ketoreductase-catalyzed reductions. From an applicability point of view, both enantiomers of the product aryl alcohols could be prepared via reduction catalyzed by one or more of the ketoreductases in most cases.     

Synthesis of 3,5-ditert-butyl-4-hydroxybenzoates and their thermal antioxidation behavior for polypropylene

Butyl 3,5-ditert-butyl-4-hydroxybenzoate (BB), octyl 3,5-ditert-butyl-4-hydroxybenzoate (OB), and dodecyl 3,5-ditert-butyl-4-hydroxybenzoate (DB) were synthesized and characterized, and their performance as antioxidant for polypropylene (PP) were also investigated. The thermooxidative stability of PP with different antioxidants were assessed by the measurements of long-term accelerated aging, differential scanning calorimetery, and thermogravimetric analysis. The results showed that 3,5-ditert-butyl-4-hydroxybenzoates could effectively inhibit the oxidation degradation of PP. And it was also found that the antioxidant efficiency of BB, OB, and DB for PP was in the order of DB > OB > BB.     

Influence of some lime-containing additives on the thermal behavior of urea

Urea is one of the main nitrogen fertilizers used in agriculture. But being well soluble in water, hardly 50% of its nitrogen is assimilated by plants. One possibility to eliminate this disadvantage is to use coating agents for modification of urea to obtain a controlled-realized fertilizer. The aim of this research was to study the influence of different lime-containing additives on the thermal behavior and decomposition kinetics of urea in oxidizing atmosphere. Commercial fertilizer-grade urea (46.4% N) and analytical-grade CaO, MgO, CaCO₃, MgCO₃ were used in the experiments. In addition, one Estonian limestone and one dolomite sample were used as additive or coating material. The experiments with a Setaram Setsys 1750 thermoanalyzer coupled to a Nicolet 380 FTIR Spectrometer by a heated transfer line were carried out under non-isothermal conditions up to 900 °C at the heating rate of 5 °C min^?1 and to calculate kinetic parameters, additionally, at 1, 2, and 10 °C min^?1 in the atmosphere containing 80% of Ar and 20% of O₂. The differential isoconversional method of Friedman was used to calculate the kinetic parameters. The results obtained indicate that thermooxidative decomposition of urea as well as the blends of urea with lime-containing materials and urea prills coated with limestone or dolomite powder follows a complex reaction mechanism.     

Synthesis of 2-(2-arylamino-3-alkyloxazolidynyl-4)- and 2-(2-arylamino-3-alkylthiazolidynyl-4-N-alkylacetamides from 2(5H)-furanone

Aminolysis of 2(5H)-furanone leads to 3-alkylamino-4-hydroxy-N-alkylbutyramides which easily form hydroxy derivatives of thiourea. The latter, depending on the protonation or quaternization site, easily undergo cyclization to thiazolidine and oxazolidine derivatives.Translated from Khimiya Geterotsiklicheskilch Soedinenii No. 12, pp. 1629–1632, December, 1985.     

Photochemical and thermal rearrangements of 2-arylamino-1-(4-tert-butylphenoxy)-9,10-anthraquinones

Photochemical transformations of 2-arylamino-1-(4-tert-butylphenoxy)-9,10-anthraquinones involve migration of thetert-butylphenyl group either to theperi-located carbonyl oxygen to give 2-arylamino-9-(4-tert-butylphenoxy)-1,10-anthraquinones or to the nitrogen atom to give 2-aryl(4-tert-butylphenyl)amino-1-hydroxy-9,10-anthraquinones (typical products of the Smiles rearrangement). Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2519–2522, December, 1998.     

Synthesis and activity of aryl benzyl methyl sulfonium salts as cationic initiators: Effect of substituent on aryl group

Benzyl o-, m-, and p-substituted phenyl methyl sulfonium salts ( 2b – 2g ) were synthesized and their activities as cationic initiators were evaluated in the bulk polymerization of phenyl glycidyl ether (PGE). Especially, their activities were estimated with respect to the effect of substituents on the aryl groups. In the polymerizations of PGE with a series of benzyl p-substituted phenyl methyl sulfonium salts, the order of their activities was found to be 2c (CH₃OCOO) > 2b (CH₃COO) > 2d (CH₃O) ～ 2a (HO). In particular, 2c was the most active initiator of all, capable of initiating the polymerization of PGE even at room temperature. In the polymerizations with 2a, 2e (m-Cl), 2f (o-CH₃), and 2g (m-CH₃), the activity of 2e was the highest of all while those of 2a, 2f , and 2g were almost the same. These results strongly suggested that the electron-withdrawing group placed on the aryl group undoubtedly enhanced the activity of the sulfonium salts as the cationic initiators.     

Regiochemical substituent switching of spin states in aryl(trifluoromethyl)carbenes

Although aryl(trifluoromethyl)diazirines have achieved great popularity in photoaffinity labeling applications, the properties of the corresponding carbenes have not been as widely explored. Here, low-temperature matrix-isolation spectroscopy and reactivity studies indicate that in contrast to m-methoxyphenyl(trifluoromethyl)carbene and most known aryl(CF(3))carbenes, the para isomer is a ground-state singlet rather than triplet. DFT calculations support these results as well as the notion that the p-CH(3)O group stabilizes the singlet carbene via resonance. These results may have relevance to the wide range of substituted aryl(CF(3))diazirines in photoaffinity applications.     

Thermal Stability of 4-chloro-2-nitro- and 4-chloro-3-nitrobenzoates of Rare Earth Elements: Influence of substituent positions

The physico-chemical properties and thermal stability in air of rare earth element 4-chloro-2-nitro- and 4-chloro-3-nitrobenzoates of the general formulae Ln(C₇H₃NO₄Cl)₃2H₂O were compared and the influence of the position of the Cl and NO₂ substituents on their thermal stabilities was investigated. The complexes of both series are crystalline, hydrated salts with colours typical of Ln³⁺. The carboxylate group in these complexes is a bidentate, chelating ligand. The NO₂ group in the chloronitro complexes does not undergo isomerization. The thermal stabilities of the 4-chloro-3-nitrobenzoates of rare earth elements were studied in the temperature range 293–1173 K, but those of 4-chloro-2-nitrobenzoates of those elements were studied only at 293–523 K because they decompose explosively above 523 K. The positions of the Cl and NO₂ substituents on the benzene ring influence the thermal properties of the complexes and their decomposition mechanisms. The different thermal stabilities of the complexes are connected with various inductive and mesomeric effects of the Cl and NO₂ substituents on the electron density in benzene ring.This revised version was published online in November 2005 with corrections to the Cover Date.     

热处理条件对煤中硒释放行为的影响

利用固定床热解反应装置,研究了平朔、兖州、神华、黑代沟、义马、霍林河和曲靖七种煤中硒在氮气气氛下,200℃～1000℃的热稳定性,考察了加热速率、终温停留时间、气氛（氮气、空气与氢气）对黑代沟和霍林河煤中硒释放规律的影响。结果表明,热解条件下煤中硒主要在700℃以下释放,700℃时的释放率为34%～63%。烟煤中硒的释放峰温在500℃左右,而褐煤中硒的释放峰温在400℃左右。500℃以上,加热速率对煤中硒的释放有一定的影响,较低的加热速率可获得较高释放率;终温1000℃时,停留时间从0延长至15min可明显提高硒的释放率,继续延长停留时间,硒的释放率没有进一步提高。与氮气气氛相比,空气气氛明显促进硒的释放,氢气气氛次之。在热解实验条件下,七种煤中的硒均没有在半焦中富集。     

Synthesis of Pd-CNT nanocomposites and investigation of their catalytic behavior in the hydrodehalogenation of aryl halides

A catalytic system based on Pd-CNT nanocomposites for the hydrodehalogenation of aryl halides is described. Thiol groups were utilized as linkers to secure the Pd nanoparticles without agglomeration. The Pd-CNT nanocomposites effectively promoted the hydrodehalogenation of aryl halides at a low Pd content (∼2.3%) and in the absence of any ligand. The results suggest that the CNTs could significantly influence the catalytic activities of CNT-supported metal catalysts for hydrodehalogenation.