The rate of cyclization of 2′- and 4′-substituted diphenylamine-2-carboxylic acids in sulfuric acid as a function of the electronic properties of substituents

The kinetic regularities of cyclization of 2′- and 4′-substituted diphenylamine-2-carboxylic acids in sulfuric acid were determined. The rate of cyclization of diphenylamine-2-carboxylic acids is linearly dependent on the nature of substituents in the meta-position relative to the reaction site in accordance with the two-parameter Hammett equation.     

Tetrazoles. 9. Acid-base properties of 5-substituted tetrazoles

The basicities of series of 5-R-tetrazoles in aqueous solutions of sulfuric acid were studied by UV and PMR spectroscopy. The pK_BH ⁺ values of these compound correlate with the _p substituent constants. The transmission factor of the p-phenylene ring (' = 0.23) was calculated from the ratio of the reaction constants for protonation of substituted 5-phenyltetrazoles and 5-R-tetrazoles. A linear dependence between the pK_a values and the pK_BH ⁺ values of 5-substituted tetrazoles was established.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 559–562, April, 1981.     

Protolytic equilibrium of certain annelated azoloazines

The first and second protonations of annelated azoloazines have been investigated quantitatively in aqueous solution. Compounds investigated were pyrazolo[1,5-a]pyrimidine (pK_BH ^– 0.03±0.02, pK_BH ²⁺ –7.87±0.30), 1,2,4-triazolo[4,3-b]-1,2,4-triazine (pK_BH ⁺ –0.04±0.02, pK_BH ²⁺ –8.00±0.10), 1,2,4-triazolo[1,5-a]pyrimidine (pK_BH ⁺ 0.21±0.03, pK_BH ²⁺ –9.00±0.09) and its 6R derivatives (R=NO₂, Br, Cl). The annelated azoloazines studied are weaker bases than their unannelated analogs. According to quantum chemical calculations (AM1), protonation of these heterocycles may occur both at the azole and the azine fragments of the molecule.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 816–824, June, 2000.     

Basicity of 2-phenyl-5-R-1,3,4-oxadiazoles

We have studied the basicity of 2-phenyl-5-R-1,3,4-oxadiazoles (R = H, Me, CH₂Ph, t-Bu, CH₂Cl, CCl₃, CF₃) in aqueous sulfuric acid solutions. These compounds are weak organic bases (pK_BH ⁺ is −1.8 to −5.2). The values of pK_BH ⁺ determined on the H₀ and X acidity function scales agree well with each other. The substituent at the 5 position has a substantial effect on the basicity of the 1,3,4-oxadiazole ring. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 748–756, May, 2006.     

Research on 6- and 7-substituted 2-and 4-thioquinolones. Transmission of the electronic effects of substituents in the benzene ring of thioquinolones to the reaction center

The electronic effect of substituents on the acid-base properties of 6- and 7-substituted 2-thionolepidines and 4-thionoquinaldines were investigated. It is shown that the pK _a (–H⁺) values for 6- and 7-substituted 2- and 4-thioquinolones and the pK _a (+H⁺) values for 7-substituted 2-thionolepidines and 6-substituted 4-methylmercaptoquinaldines correlate with the _M substituent constants of Jaffe and Taft. The effect of a substituent is transmitted primarily via an inductive mechanism, regardless of its position.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 399–402, March, 1974.     

Acetyl transfer from N-acetyloxypyridinium cations to 4-(4′-N,N-dimethylaminostyryl)-pyridine N-oxide and 4-dimethylaminopyridine

Kinetic data are given for the transfer of the acetyl group from the N-acetyloxypyridinium cations of tetraphenylborate salts to 4-(4′-N,N-dimethylaminostyryl)pyridine N-oxide and 4-dimethylaminopyridine in acetonitrile solution. Structural factors were found to affect the rate constants and activation parameters. Correlation equations are given relating the acetyl transfer rate constants with pK_BH+ values of the leaving group and frequencies of the carbonyl vibrations of the salts. Translated from Teoreticheskaya i éksperimental’naya Khimiya, No. 2, pp. 75–77, March–April, 1997.     

Synthesis of 6′-carbamoylmethylthio-5′-cyano-1′,4′-dihydro-3,4′-bipyridine-3′-carboxylic and 6′-carbamoylmethylthio-5′-cyano-1′,4′-dihydro-4,4′-bipyridine-3′-carboxylic esters and investigation of their stability. 2. Esters of 6′-carbamoylmethyl-thio-5′-cyano-1′,4′-dihydro-4,4′-bipyridine-3-carboxylic acids

The stability of solutions of esters of 6′-carbamoylmethylthio-5′-cyano-2′-methyl-1′,4′-dihydro-4,4′-bipyridine-3′-carboxylic acids was investigated by HPLC. The corresponding esters of 6′-carbamoylmethylthio-5′-cyano-4,4′-bipyridine-3′-carboxylic acids,esters of 8-cyano-5-methyl-3-oxo-7-(4-pyridyl)-2,3-dihydro-7H-thiazolo-[3,2-a]pyridine-6-carboxylic acids, methyl 3-amino-2-carbamoyl-6-methyl-4-(4-pyridyl)-4,7-dihydrothieno[2,3-b]pyridine-5-carboxylate, and methyl 3-amino-2-carbamoyl-6-methyl-4-(4-pyridyl)-thieno[2,3-b]pyridine-5-carboxylate were synthesized as standard compounds (typical impurities). Analysis by HPLC was realized under the conditions of reverse-phase chromatography. It was established that solutions of the investigated compounds (with mixtures of acetonitrile with phosphate buffer, having pH values of not less than 3 and not more than 5, as solvents) are stable for one month when the solutions are stored in a place protected against light. It is also necessary to use chromatographic systems in which the aqueous components have pH 3–5 during determination of the purity of the esters of 6′-carbamoylmethylthio-5′-cyano-2′-methyl-1′,4′-dihydro-4, 4′-bipyridine-3′-carboxylic acid by HPLC in order to separate the analyzed sorbates and their typical impurities more completely. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 841–848, June, 2007.     

Tetrazoles. 10. Acid-base properties of 5,5′-ditetrazolyls

The constants of detachment (pK_a 1.41 and 4.25) and addition (pK_BH –5.47 and –10.91) of protons for 5,5-ditetrazolyl and of protonation of 1,1-diphenyl-5,5-ditetrazolyl (pK_BH+ –7.47) in aqueous solutions were determined by spectrophotometric and potentiometric methods. By comparison of the acid-base properties of the two compounds it was established that the latter exists in the trans form.See [1] for Communication 9.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1563–1566, November, 1981.     

Heterocycles containing tellurium and nitrogen. 5. Basicity constants of benzazoles

The basicities (pK_BH+) of monotypically substituted 2-R-benzochalcogenazoles increase regularly on passing from benzoxazoles to benzotellurazoles.See [1] for Communication 4.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 836–837, June, 1991.     

Solvent Effect on Deprotonation Equilibria of Acids of Various Charge Types in Non-aqueous Isodielectric Mixtures of Protic Ethylene Glycol and Dipolar Aprotic N,N-Dimethylformamide at 298.15 K

Deprotonation constants of phthalic (H₂A) and biphthalic (HA⁻) acids and of mono-protonated (BH⁺) and di-protonated (BH₂²⁺) piperazine acids have been determined at 25 °C by measuring the Emf of galvanic cells comprising H⁺-sensitive glass GE(H⁺) and Ag,AgCl electrodes in non-aqueous isodielectric mixtures of protic ethylene glycol (EG) and dipolar aprotic N,N-dimethylformamide (DMF). Solvent effects on deprotonation of the acids: ∂(ΔG _diss^o)=2.303RT[p(_s K _a)−p(_R K _a)], have been dissected into transfer Gibbs energies, ΔG _t^o _, of the species involved by evaluating ΔG _t^o of the uncharged phthalic acid and base piperazine (B) from the measured solubilities of the acid and base, respectively, and using ΔG _t^o of H⁺ based on the TATB reference electrolyte assumptions, as evaluated earlier. The contributions of the different species involved in the protolytic equilibria i.e., H⁺,H₂A,HA⁻,BH₂²⁺ and BH⁺ and their respective conjugate bases HA⁻,A²⁻,BH⁺ and B have been discussed in terms of their solvation behavior as guided by the ‘acid-base’, dispersion, structural and electronic characteristics of the acid-base species and of the co-solvent molecules and binary mixtures, ignoring the Born-type electrostatic interactions on the ionic species as the solvent system is quasi isodielectric.     

Alkylation of salts ofN-(β-hydroxyalkyl)-N′-hydroxydiazeneN-oxides with alkyl halides and dimethyl sulfate

Salts ofN-(β-hydroxyalkyl)-N′-hydroxydiazeneN-oxides, RCH(OH)CH₂N(O)=NO⁻ M⁺ (R=Me, Prⁱ, or Bu^t; and M=Li, Na, K, Ag, NH₄, or Me₄N), were prepared. Their alkylation with alkyl halides R′X (X=Cl, Br, or I) and dimethyl sulfate was studied. Generally, alkylation afforded mixtures ofN-(β-hydroxyalkyl)-N′-alkoxydiazeneN-oxides RCH(OH)CH₂N(O)=NOR′ andO-alkyl-N-(β-hydroxyalkyl)-N-nitrosohydroxylamines RCH(OH)CH₂N(NO)OR′. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1996–2001, October, 1998.     

Synthesis and characterization of the [Cu(Cin2bda)2]ClO4 and [Cu(Ncin2bda)2]ClO4 complexes: Crystal structure of [Cu(Ncin2bda)2]ClO4

Two copper(I) complexes [Cu(Cin₂bda)₂]ClO₄ (I) and [Cu(Ncin₂bda)₂]ClO₄ (II) have been prepared by the reaction of the ligands N²,N²′-bis(3-phenylallylidene)biphenyl-2,2′-diamine (L¹) and N²,N²′-bis[3-(2-nitrophenyl)allylidene]biphenyl-2,2′-diamine (L²) and copper(I) salt. These compounds were characterized by CHN analyses, ¹H NMR, IR, and UV-Vis spectroscopy. The C=N stretching frequency in the copper(I) complexes shows a shift to a lower frequency relative to the free ligand due to the coordination of the nitrogen atoms. The crystal and molecular structure of II was determined by X-ray single-crystal crystallography. The coordination polyhedron about the copper(I) center in the complex is best described as a distorted tetrahedron. A quasireversible redox behavior was observed for complexes I and II. The article is published in the original.     

Kinetics of the reaction of sodium arylthiolates with nitro-carboxybenzyl halide derivatives

The rate constants for the reactions of 4-halomethyl-3-nitrobenzoic acids, the nonnitro derivatives, and their ethyl esters with arylthiolates were measured at different temperatures. It was found that the retardation in rate constants compared to benzyl halides is due to the electrostatic repulsion between the electronegative substituents (COO⁻ and/or NO₂) in the substrates and thiolate ions. Good correlations between log k₂ values of the acids and carbon basicities of thiolates were found while log k₂ values of the esters show good straight lines with Hammett σ constants, pk_a, and carbon basicities of arylthiolates. © 1996 John Wiley & Sons Inc     

Synthesis, characterization and properties of β-octamolybdate-supported transition metal complexes with mixed ligands: [Cu(2,2′-bipy)(C6H5NO2)(H2O)]2[Mo8O26]·5H2O

A novel organic–inorganic hybrid compound [Cu(2,2′-bipy)(C₆H₅NO₂)(H₂O)]₂[Mo₈O₂₆]·5H₂O (1), (2,2′-bipy = 2,2′-bipyridine; C₆H₅NO₂ = pyridine-4-carboxylic acid) has been prepared and characterized by elemental analyses, IR spectrum, thermal stability analysis, and single-crystal X-ray diffraction. Compound 1 is a discrete cluster, constructed from β-[Mo₈O₂₆]⁴⁻ subunits covalently bonded to two [Cu(2,2′- bipy)(C₆H₅NO₂)(H₂O)]₂⁴⁺ coordination cations via terminal oxo groups that connect one molybdenum site. A 3D supramolecular network is further formed by extensive hydrogen bonding interactions and π–π interactions of the 2,2′-bipy and pyridine-4-carboxylic acid ligands. EPR and magnetic susceptibility studies have been used to elucidate the electronic properties of the Cu²⁺ centres, and the results are in good agreement with the structural features of the compound.     

Synthesis and investigation of the stability of esters of 6′-carbamoylmethylthio-5′-cyano-1′,4′-dihydro-3,4′-and-4,4′-bipyridine-3′-carboxylic acids 1. Esters of 6′-carbamoylmethylthio-5′-cyano-1′,4′-dihydro-3,4′-bipyridine-3′-carboxylic acids

Esters of 6′-carbamoylmethylthio-5′-cyano-1′,4′-dihydro-3,4′-bipyridine-3′-carboxylic acids are obtained by the alkylation of piperidinium 3′-alkoxycarbonyl-5′-cyano-1′,4′-dihydro-3,4′-bipyridine-6′-thiolates with iodoacetamide. For an HPLC study of the stability of solutions of the abovementioned 1,4-dihydrobipyridines (solution pH 2.3–9.0) the appropriate esters of 6′-carbamoylmethylthio-5′-cyano-3,4′-bipyridine-3′-carboxylic acids and esters of 8-cyano-5-methyl(or phenyl)-3-oxo-7-pyridin-3-yl-2,3-dihydro-7H-thiazolo[3,2-a]pyridine-6-carboxylic acids were synthesized as reference compounds. Analysis by HPLC was carried out under conditions of reverse-phase chromatography. It was shown that solutions of the investigated compounds in a mixture of acetonitrile and phosphate buffer (pH 3.0–5.0) were stable for 1 month on storage protected from light. Under the action of light in all the solutions investigated irrespective of pH the formation occurs of the corresponding esters of 6′-carbamoylmethylthio-5′-cyano-3,4′-bipyridine-3′-carboxylic acids. The presence of esters of 8-cyano-5-methyl(or phenyl)-3-oxo-7-pyridin-3-yl-2,3-dihydro-7H-thiazolo[3,2-a]pyridine-6-carboxylic acids (no more than 4%) was detected only in 0.1% solutions of phosphoric acid (pH 2.3) under conditions of storage of the latter protected from light. A series of as yet unidentified products was detected in solutions of pH 7.0–9.0. Dedicated to E. Lukevics on his 70th birthday __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 59–68, January, 2007.     

Kinetics and mechanism of oxidation of uric acid with thallium(III) in acetate buffers

The kinetics of oxidation of uric acid by thallium(III) has been studied in acetate buffers; the oxidation products are alloxan and urea. Deprotonated uric acid, UaH⁻, and T1(OAc)₃ are the reacting species. A probable reaction mechanism has been proposed conforming with rate law (1)-d[T1^III]/dt=(k′₁K′₁+k′₂K′₂K₁/[H⁺]) [T1^III][UaH₂]/1+K₄[OAc⁻] A comparative analysis with other soft acids Hg^II and Pb^IV has been attempted.     

Kinetic and equilibrium study of the deprotonation of 4-nitrophenyl[bis(ethylsulphonyl)]methane by organic bases in acetonitrile in the presence of common cation BH<Superscript>+</Superscript> and tetrabutylammonium perchlorate

The results of kinetic and equilibrium experiments with the set of reaction of proton abstraction from 4-nitrophenyl[bis(ethylsulphonyl)]methane in acetonitrile are reported. Two strong organic bases are used: 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) and 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD). The rates of proton transfer reaction have been measured by T-jump method in the presence of perchlorate of the appropriate base as a common cation BH⁺ and supporting electrolyte-tetrabutylammonium perchlorate (TBAP) in the temperature range between 20–40°C are: k _H =1.32×10⁷−2.00×10⁷ and 2.82×10⁷−4.84×10⁷ dm ³mol⁻¹s⁻¹ for MTBD and TBD respectively. The enthalpies of activation ΔH _MTBD ^≠ =13.5 and ΔH _TBD ^≠ =18.1 kJmol⁻¹. The entropies of activation are negative: ΔS _MTBD ^≠ =−62.3 and ΔS _TBD ^≠ =−40.3 Jmol⁻¹K⁻¹. The change of the absorbance of the anion of 4-nitrophenyl[bis9ethylsulphonyl)]methane at the temperature 25°C in the presence of common cation BH⁺ gives the equilibrium constants K=705 and 906 M⁻¹ for MTBD and TBD respectively. Kinetic and equilibrium results are discussed. The possible mechanism of proton transfer reaction between 4-nitrophenyl[bis(ethylsulphonyl)]methane and cyclic organic bases: MTBD and TBD in acetonitrile is proposed.     

Computational study of topological effects on intramolecular electron transfer in mixed-valence compounds

The constrained density functional theory (CDFT) was used to investigate the topological effects on intramolecular electron transfer processes that have been reported in previous experimental work [Inorg. Chem., 1997, 36 (22), pp 5037–5049]. The computation mainly focused on three isomers of diferrocenylbenzenes (ortho, para, and meta) and 5-substituted derivatives of m-diferrocencylbenzenes with R = NH₂, Cl, CH₃, CN, NO₂, NeCH₃)₃³⁺, and N₂⁺. The influence of a third group R′ (R′ = NH₂ and N₂⁺) was introduced to the ortho and para isomers. The calculations were compared with the experimental results. The relation between the substituted functional groups and the effectiveness of intramolecular electron transfer was discussed on the basis of CDFT computational results.     

Asymmetric synthesis of β-N-substituted α,β-diamino acidsvia a chiral complex of NiII with a dehydroalanine derivative

Asymmetric synthesis of β-N-substituted (S)-α,β-diamino acids was accomplished by Michael addition of amines to the Ni^II complex of the Schiff base derived from (S)-2-[N-(N′-benzylprolyl)amino]benzophenone (BPB) and dehydroalamine. Diastereoselectivity of the reaction is kinetically and thermodynamically controlled. The chiral auxiliary reagent, BPB, can be recovered and reused. Translated fromIzvestiya Akademii Nauk. Serya Khimicheskaya, No. 3, pp. 504–507, March, 1997.     

Basicities and tautomerism of 4,4,6-trimethyl-2-aryl-amino-4H-1, 3-thiazines

The relative basicities of 4,4,6-trimethyl-2-arylamino-4H-1,3-thiazines, which are capable of amine-imine tautomerism, and of model compounds with fixed amino and imino structures were determined by potentiometric titration in methanol. Good correlation was observed between the pK_a values and the Hammett σ constants in the investigated reaction series. The anomalous pK_a values of the model amines and imines are explained by the different character of the electronic interactions in them, which is due to the change in the three-dimensional orientation of the aromatic ring and the amidine fragment.