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The synthesis of a new symmetric bis(spiropyran) of the indoline series existing as an equilibrium mixture of isomeric forms in various organic solvents is described. This equilibrium was in detail studied by dynamic NMR spectroscopy. In particular, the equilibrium constants were found at various temperatures, and the thermal effects of isomerization processes were calculated. The thermal transformations were studied by quantum chemical modeling. As a result, possible isomerization pathways were proposed and the observed ratio of the forms in the NMR spectra was explained. Photo- and thermochromic transformations were studied by UV spectroscopy, which revealed positive photochromic properties of the target compound. The observed changes in the absorption spectra with increasing temperature are completely consistent with the results of NMR studies. The nature of the absorption bands observed in the spectra was explained using time-dependent density functional theory (TD-DFT) calculations. The surface-enhanced Raman scattering (SERS) spectra of the synthesized compound on the surface of silver nanoparticles were detected and analyzed before and after UV irradiation to determine prospects for using similar bis(spiropyrans) as SERS markers and probes. [ABSTRACT FROM AUTHOR]

Reactions of 12H-quinoxaline[2,3-b]phenoxazine (QOPO) derivatives with the CoII and ZnII hexafluoroacetylacetonates accompanied by protonation of the starting bases result in stable complexes [QOPOH]+[M(hfac)3]− whose structure was determined by X-ray diffraction and by 1H and 15N NMR spectroscopy. The complexes are characterized by long-wavelength absorption (560–664 nm) and fluorescence in the red region (λfl = 674–805 nm). The relative energies of the protonated tautomers N(14)—H and N(7)—H were determined using the results of B3LYP–D3BJ/6-311G++(d,p) density functional calculations with inclusion of D3BJ dispersion correction. A SQUID magnetometry study of the static and dynamic magnetic properties of the CoII complex revealed that it behaves as a field-induced single-ion magnet. [ABSTRACT FROM AUTHOR]

The Сd(II) complexes with redox amphoteric 2,6-di-(tert-butyl)-4-((2-hydroxyphenyl)imino)cyclohexa-2,5-dienone ligands L1 and L2 (adducts I, II, and III) are synthesized. The structures of coordinated complexes I, II, and III are determined by X-ray diffraction (XRD) (CIF files CCDC nos. 1838319 (II) and 1838310 (III)) and confirmed by the 1Н, 13С, and 113Cd NMR spectroscopy (for complexes I and III) and IR spectroscopy data. [ABSTRACT FROM AUTHOR]

The mechanochemical fluorination of naproxen and its salts (Li, Na, and K) with 1-(chloromethyl)-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate) (Selectfluor, F–TEDA–BF4) was studied. The reaction of naproxen with an excess of Selectfluor gives 2-(5,5-difluoro-6-oxo-5,6-dihydronaphthalen-2-yl)propionic acid in high yield. Small additives of Al2O3, SiO2, M2CO3 (M = Na, K, Rb, Cs), ionic liquids (ILs), crown ethers, and N-bases accelerate the reaction of naproxen with Selectfluor and increases the monofluorination/difluorination product ratio. [ABSTRACT FROM AUTHOR]

2,3-Dihydro-1H-imidazo[1,2-a]benzimidazole in acetic acid, and its N1-Me derivative in CHCl3, are brominated at position 6 with bromine. Less nucleophilic N9-R derivatives do not enter into the reaction under these conditions, but, like their N1-R isomers, they are quite effectively brominated by the KBrO3–HBr system, but at position 7, probably due to the transition of the reaction to the mode of bromination of protonated forms of substrates. N1- and N9-alkyl-6(7)-Br-2,3-dihydroimidazo[1,2-a]benzimidazoles can also be obtained by N-alkylation of 6(7)-Br-2,3-dihydroimidazo[1,2-a]benzimidazoles under neutral or basic conditions. [ABSTRACT FROM AUTHOR]

A condensation reaction between formyl-containing spiropyrans and iodides of 1,2,3,3-tetramethyl-3H-indolium derivatives was studied. The reaction results in a mixture of products with a strong predominance of one of them irrespective of the structure of the starting compounds. The structures of the compounds formed during the reaction were determined based on the NMR, IR, and mass spectroscopy data. The dependence of the yield of the major reaction product on the structure of the starting compounds was studied. The prerequisites for the observed reaction pathway were established and the reaction mechanism was proposed using the results of quantum-chemical calculations based on analysis of the molecular electrostatic potential and the dual descriptor of reactivity. [ABSTRACT FROM AUTHOR]

A series of new derivatives comprising heteropentacyclic 12H-quinoxalino[2,3-b]-phenoxazine (QOPO) system and functionalized with arylamide anchoring groups was synthesized. Their photostability as well as the spectral, luminescent, electrochemical, and optoelectronic properties were studied both in composites prepared by adsorption of QOPO onto the TiO2 surface and in solution. Attachment of the amide anchoring groups to the QOPO core provides high adsorption of the compounds and the onset of photovoltaic properties that were not observed in the unfunctionalized precursors. However, these groups do not provide efficient injection of excited electrons into the conduction band of the semiconductor. According to B3LYP/6-311++G(d,p) density functional calculations of the model nanoclusters QOPO/(TiO2)10, efficient electron injection and, as a consequence, high photovoltaic conversion efficiency of dye-sensitized solar cells require delocalization of the LUMO of the QOPO/TiO2 system over both structural fragments. Relevant anchoring groups are proposed. [ABSTRACT FROM AUTHOR]

This work focuses on the formyl derivative of 2-oxaindane series spiropyran under its condensation reaction. The data indicated that all products are thermodynamically stable enamine-ketone tautomeric form in both DMSO solution and solid state. This finding can be explained by the migration of proton in 7-hydroxy group to the azomethine nitrogen, which is conjugated with electrocyclic opening of the spirounit in the non-stable Schiff-bases. We observe the enamine-ketones dynamic equilibrium of Z-, E-isomers in the DMSO solution. X-Ray diffraction study was performed for single crystalline sample of aminoethanol derivative. The synthesized compounds were evaluated in vitro cytotoxic activity against four typical human cell lines, showing moderate activity against lung carcinoma (LU-1), hepatocellular carcinoma (Hep-G2), breast carcinoma (MCF-7), and undifferentiated thyroid carcinomas (8505c). Among them, the compound with R = i-Pr showed the best activity with IC50 values 10.60 (MCF-7), and 10.55 µM (8505c). The in vitro antioxidant activity test using 1,1-diphenyl-2-picrylhydrazyl (DPPH) showed that all the synthesized compounds have weak or no activity. [ABSTRACT FROM AUTHOR]

The product of 3-formyl-2-quinolone condensation with trimethylammonium chloride acethydrazide, (H2L+)Сl– hydrazone, was synthesized. Complexes of Zn(II) and Cu(II), [M(HL)OCH3]ClO4, with a distorted square-planar strucrure of coordination sites and asymmetric chelate сomplexes of Mn(II), Ni(II), and Co(II), [M(HL)(H2L)]·(ClO4)3, of pseudo-octahedral structure were obtained on its basis. The protistocidal, antibacterial, and fungistatic activities of the synthesized compounds were studied. [ABSTRACT FROM AUTHOR]

The reaction of fluorescein-substituted 2-hydroxybenzaldehyde with 3H-indolium perchlorate has led to the formation of 1,3-dihydrospiro[indole-2,2′-chromene] bearing a fluorescein fragment at position 8 of chromene. In a solution, the obtained compound has existed in the cyclic form and has exhibited photochromic properties. Adding transition metal perchlorates to the spiropyran solution has led to intense coloration due to the complex formation. Zinc and cadmium complexes of the spiropyran have exhibited red fluorescence and negative photochromism. [ABSTRACT FROM AUTHOR]

Isonicotinic acid N′-(10-oxo-10H-phenanthren-9-ylidene)hydrazide (HL) and its complexes ML2 and MHLCl2 [М = Cu(II), Ni(II), Co(II), Fe(II), and Zn(II)] were synthesized. The structure and properties of the obtained compounds were studied by 1H NMR, IR, and X-ray absorption spectroscopy. The hydrazide structure was determined by X-ray diffraction. Quantum-chemical calculations of its tautomeric forms and electronic absorption spectra were carried out. In ML2 chelate complexes, the ligand is coordinated to metal atoms in the enol form, whereas in MHLCl2 complexes it is coordinated in the keto form. [ABSTRACT FROM AUTHOR]

β-Aminovinyl ketone (2-nitro-3-(8-quinolylamino)prop-2-enal) was synthesized by condensation of nitromalondialdehyde with 8-aminoquinoline. The reactions of β-aminovinyl ketone with copper, nickel, and cobalt acetates in methanol gave metal complexes. The spectral and magnetic characteristics of preparatively isolated compounds were studied. The structure of cobalt(II) chelate was determined on the basis of X-ray diffraction study (CIF file CCDC no. 2109263). [ABSTRACT FROM AUTHOR]

Literature data on electrophilic and oxidative fluorination of heterocyclic compounds have been analyzed in terms of the "green" chemistry principles. Particular attention has been paid to reaction mechanisms and selectivity problem. [ABSTRACT FROM AUTHOR]

The complex formation properties of the product 2-oxo-1,2-dihydroquinoline-3-carbaldehyde condensation with stearic acid hydrazide towards Cu(II) and Ni(II) ions has been studied. Composition and structure of the complexes has been found dependent on the nature of the metal and acid residue. The obtained compounds have been investigated by spectral methods, the temperature dependence of the magnetic susceptibility in constant magnetic field has been measured. Quantum-chemical simulation of possible isomers of N'-acylhydrazone in a solution has been carried out. [ABSTRACT FROM AUTHOR]

New azomethine 1-(2-hydroxybenzylidenamino)benzimidazolinone-2 and Cu(II), Co(II) and Zn(II) complexes based on it are synthesized and studied. The structure of azomethine and metal complexes is found from the data of elemental analysis, infrared (IR) spectroscopy, 1H NMR spectroscopy, X-ray absorption spectroscopy, and magnetochemistry. It is shown that all complexes have a mononuclear structure with the general formula M(HL)2. For the copper complex, the weak antiferromagnetic-type exchange between copper ions is observed due to the formation of intermolecular hydrogen bonds N–H···O=C. [ABSTRACT FROM AUTHOR]

1-Allyl(2-bromopropyl)-3-carboxy(carbalkoxy)methyl-2-aminobenzimidazolium halides and their 2-iminobenzimidazoline forms were synthesized. Their cyclization into functionalized imidazo[1,2-a]benzimidazole derivatives was studied. Some further transformations of obtained imidazobenzimidazoles with the participation of reactive substituents and an activated methylene group were studied. [ABSTRACT FROM AUTHOR]

New potential biologically active derivatives, in which the sterically hindered pyrocatechol moiety is linked through a 2-thioacetyl covalent bridge to a number of secondary amines, pharmacophore γ-aminobutyric acid, and 2-amino-4-dimethylamino-1,3,5-triazine, were synthesized. The structures of most of the synthesized compounds were studied by X-ray diffraction. [ABSTRACT FROM AUTHOR]

The review generalizes and analyzes published data on carbocation catalysis of organic reactions. Particular attention has been paid to reaction mechanisms and selectivity problems. [ABSTRACT FROM AUTHOR]

New potentially bioactive derivatives comprising spatially hindered pyrocatechol linked to hydrazine, acid hydrazides (including isoniazid), and acetylcysteine by a covalent bridge, have been obtained. The structure of the obtained compounds was studied by X-ray diffraction analysis. [ABSTRACT FROM AUTHOR]

9-Substituted 2-(5-nitrofuran-2-yl)-9H-imidazo[1,2-a]benzimidazoles were synthesized for the first time by cyclization of quaternary salts obtained from 1-substituted benzimidazol-2-amines and 2-bromo-1-(5-nitrofuran-2-yl)ethan-1-one. 9-R-2-Methyl(aryl)-9H-imidazo[1,2-a]benzimidazoles reacted with 5-nitrofuran-2-carbaldehyde and 4-nitrobenzaldehyde to give the corresponding secondary alcohols as a result of aldehyde addition to the 3-position of the tricyclic system. The Witting olefination of ethyl 2-(bromomethyl)-9-methyl-9H-imidazo[1,2-a]benzimidazole-3-carboxylate afforded 2-ethenylimidazo[1,2-a]benzimidazoles. [ABSTRACT FROM AUTHOR]

Novel complexes of Zn(II), Cd(II), Ni(II), and Co(II) with 3,5-di-tert-butyl-1,2-benzoquinone 3-hyd-roxynaphthoyl hydrazone have been synthesized. Composition, structure, magnetic and spectral properties of the obtained compounds have been studied by means of elemental analysis, IR, 1H NMR, and UV spectroscopy, X-ray diffraction analysis, quantum-chemical simulations, and magnetochemistry. [ABSTRACT FROM AUTHOR]

The acylation of N-substituted 3-methyl-1H-1,2-diazaphenalenes of the naphthalene and acenaphthene series with trifluoroacetic anhydride gave mono- and diacylated products. Despite the presence of a bulky substituent on the pyrrole type nitrogen atom, the trifluoroacetyl group entered the peri position with respect to that substituent. The product structure was confirmed by X-ray analysis. [ABSTRACT FROM AUTHOR]

A new Schiff base was prepared by the reaction of 4-methyl-7-hydroxy-8-formylcoumarin with N-aminomercaptotriazole. In solution and in solid phase the compound was shown to exist in the thione form. The compound reacts with Cu(II), Ni(II), Zn(II) and Cd(II) ions depending on the metal salt to give complexes of composition ML2 or MHLX, where HL is monodeprotonated form of the ligand. Cu(II) and Ni(II) complexes were studied by spectral and magnetochemical methods. The Zn(II) and Cd(II) complexes exhibit fluorescence. [ABSTRACT FROM AUTHOR]

By the reaction of 2-chloroindole-3-carbaldehyde with acylhydrazones new acylhydrazones of the indole series have been synthesized, and their structure, the possibility of cyclization to pyrazoloindoles, and complexing properties have been studied. By means of quantum chemical DFT calculations taking into account the solvent effect it was shown that the reaction of 2-chloroindole-3-carbaldehyde and the corresponding acylhydrazine is an exothermic process, irrespective of which final product is formed, indolemethylenehydrazide or pyrazoloindole. Therefore, both possible transformations in the studied reacting system are controlled kinetically and not thermodynamically. [ABSTRACT FROM AUTHOR]

Novel spirobenzopyranindolines containing a rhodamine fragment linked to a benzopyran fragment with an aminomethylene spacer were synthesized by the reaction of 7-hydroxy-6-formyl-substituted spiropyrans and rhodamine B hydrazide. The synthesized spiropyrans in toluene and acetone are present in the spiropyran‒spirolactam form. The 5-methyl-substituted was the only to exhibit photochromism. Adding Zn(II), Ni(II), Co(II), and Cd(II) perchlorates to the spiropyran solutions leads to intense coloration due to complex formation. [ABSTRACT FROM AUTHOR]

1-Amino-2-hydrazinobenzimidazole when treated with carbon disulfide underwent a regioselective cyclization involving the hydrazino group to form 9-amino-2,9-dihydro-3 Н-[1,2,4]triazolo[4,3- а]benzimidazole-3-thione. Being an N-amine this compound gives Schiff bases with aromatic aldehydes, and as thione in DMF at a temperature not exceeding 60°С it is successfully alkylated, particularly by functionalized alkylating agents, affording the corresponding sulfanylmethyl derivatives. In boiling DMF, as it is demonstrated by an example of benzyl chlorides, NNH group also undergoes alkylation that unexpectedly results in 4-benzylidenamino-3-benzylsulfanyltriazolobenzimidazoles. [ABSTRACT FROM AUTHOR]

The interaction of 7-hydroxy-6-formyl-substituted spiropyrans and Rhodamine B aminoethylamide has afforded spirobenzopyrans containing rhodamine fragment bound to the benzopyran part via the methyleneaminoethyl spacer. The prepared spiropyrans exist in the spiropyran-spirolactam form in the acetone solution and exhibit weak photochromism at 283 K. The addition of Cd, Co, Ni, and Zn perchlorates to the spiropyrans solution results in the coloration due to the complex formation. The composition and stability of the complexes has been determined by means of spectrophotometry. [ABSTRACT FROM AUTHOR]

The article discusses the most important aspects of the selective RF excitation of multiplet single lines, an approach that makes it possible to simplify the spectra of complex multicomponent systems, to measure the spin-spin coupling constant, and to determine molecular structure. Semi-selective and selective methods of recording spectra are considered and theoretically substantiated based on the product operator formalism. The results are verified using quantum-mechanical calculations within the framework of the density matrix formalism. The paper demonstrates that the proposed new method leads to a significant simplification of two-dimensional nuclear magnetic resonance spectra. This makes it possible to study chemical processes and spin state exchange by observing the dynamic behavior of the multiplet structure of bound nuclei. [ABSTRACT FROM AUTHOR]

4,6-Di( tert-butyl)-2-(quinolin-2-yl)-1,3-tropolone (7′) was isolated for the first time from the acid-catalyzed reaction of 2-methyl-substituted nitrogen heterocycles with 1,2-benzoquinones, which proceeds with the expansion of the o-quinone ring to give mainly isomeric 5,7-di( tert-butyl)-2-(quinolin-2-yl)-1,3-tropolone. [ABSTRACT FROM AUTHOR]

A new spirobenzopyranindoline containing a rhodamine fragment bonded by an azomethine spacer with the benzopyran fragment was synthesized based on 6-formyl-7-hydroxy-substituted spiropyran; the new compound exhibited complexation properties in solutions. [ABSTRACT FROM AUTHOR]

The reaction of 2-methylquinoline with 3,5-di- tert-butyl-1,2-benzoquinone afforded a mixture of 5,7-di- tert-butyl-3-hydroxy-2-(quinolin-2-yl)cyclohepta-2,4,6-trien-1-one and previously unknown 10- tert-butylindolo[1,2- a]quinoline-8,11-dione. The structure of the latter was determined by two-dimensional heteronuclear correlation NMR spectroscopy. [ABSTRACT FROM AUTHOR]

Condensations of alloxan with 2-methylquinoline, 2,6-dimethyl-5-nitroquinoline, and 1-methylisoquinoline were carried out under acidic conditions. Analogous reactions of alloxan with linear structures containing alkyl groups σ,π-conjugated with C=N fragments were also studied. [ABSTRACT FROM AUTHOR]

Binuclear complexes of Co(II), Сu(II), and Pd(II) with 2-(N-tosylamino)benzal-2'-(hydroxymethyl)aniline are synthesized. The compositions and structures of the ligand and complexes are determined from the data of elemental analysis, IR spectroscopy, Н, С, and N NMR spectroscopy, X-ray absorption spectroscopy, and magnetochemical measurements in a temperature range of 294-77.4 K. All complexes are dimeric. The Cu...Cu and Cо...Cо distances equal to 3.03 and 2.99 Å, respectively, are obtained for the Cu(II) and Co(II) complexes. These complexes are characterized by the antiferromagnetic exchange interaction with 2 J = -630 and -42 cm, respectively. [ABSTRACT FROM AUTHOR]

Potentially tautomeric azomethine imide, 2-[(3-oxo-5-phenylpyrazolidin-1-yl)methylidene]-1 H-indene- 1,3(2 H)-dione, has been synthesized by condensation of 5-phenylpyrazolidin-3-one with 2-(hydroxymethylidene)-1 H-indene-1,3(2 H)-dione. According to the IR, H and C NMR, and electronic absorption spectroscopy data and DFT B3LYP/6-311++G( d, p) quantum chemical calculations, the title compound in solution exists as planar tricarbonyl tautomer stabilized by intramolecular hydrogen bond between the NH proton of the pyrazolidine fragment and carbonyl oxygen atom of the indene fragment. Its crystal structure was determined by X-ray analysis. [ABSTRACT FROM AUTHOR]

New ligand systems based on 4-formyl-5-hydroxypyrazole and 1-aminobenzimidazole derivatives are synthesized. The obtained enamines and their Zn and Cd metal complexes of composition ML were investigated using the IR, heteronuclear (H, C, N, Se, Cd) and two-dimensional NMR spectroscopy (COSY, HSQC, HMBC). The data of physicochemical investigations and quantum-chemical calculations showed that the ligands exist in the ketoamine tautomeric form. Quantum-chemical simulation of Zn(II) and Cd(II) complexes showed that the zinc complexes adopt the pseudo-tetrahedral and the cadmium complexes pseudo-octahedral configuration. [ABSTRACT FROM AUTHOR]

A study by IR, electronic and NMR (Н and С) spectroscopy together with X-ray structure analysis and quantum chemical calculations using DFT B3LYP/6-31G(d,p) determined N,N´-cyclic azomethine imines - 1-(2-hydroxyphenylmethylidene)-3-oxo-5-phenylpyrazolydin-1-ium-2-yde ( 1) и 1-[(2-hydroxynaphthalene-1-yl)methylidene]-3-oxo-5-phenylpyrazolydin-1-ium-2-yde ( 2) - to exist in solutions as isomers with an intramolecular hydrogen bond between the hydroxyl group and the nitrogen of the pyrazolidone ring. Compound 1 undergoes photoexcitation in the wavelength range 363-320 nm followed by luminescence with an anomalous Stokes shift that is caused by the intramolecular excited state proton transfer mechanism (ESIPT effect). [ABSTRACT FROM AUTHOR]

Heating of an equimolar mixture of 3,5-di- tert-butyl-1,2-benzoquinone with thiosalicylic acid led to 2-[(4,6-di- tert-butyl-2,3-dihydroxyphenyl)thio]benzoic acid. In the case of β-mercaptopropionic acid, 2-[(4,6-di- tert-butyl-2,3-dihydroxyphenyl)thio]propionic acid was formed, which upon reflux in Ac2O was converted to 6,8-di- tert-butyl-9-hydroxy-3,4-dihydro-2 H-1,5benzoxathiepin-2-one. [ABSTRACT FROM AUTHOR]

Three novel palladium(II) azo complexes (I-III), whose compositions and structures were established from C, H, N, S elemental analysis and IR and H NMR spectroscopy, were synthesized by boiling palladium(II) acetate and some pyrazolazo derivatives, namely, 2- iso-propyl(phenyl)-3-methyl-4-[(4-meth-ylphenyl)diazenyl]-1H-pyrazol-5-one and 1- iso-propyl-3-methyl-4-[(4-methylphenyl)diazenyl]-1H-pyrazol-5-thione (HL) in an acetone/methanol (1: 1) mixture. X-ray diffraction analysis was performed for complexes I and III. Complex I with an NO-ligand environment was established to have a trans-planar configuration for the PdNO chelate ring, while the formation of the cis-planar structure by the PdNS chelate ring was typical for complex III. [ABSTRACT FROM AUTHOR]

The reaction of 4-chloromethyl-1-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate) with 6-methyl- and 1,3,6-trimethyluracil in water has been studied. According to the kinetic data, the fluorination follows a bimolecular mechanism with intermediate formation of cationic σ-complexes. [ABSTRACT FROM AUTHOR]

Nitrosonium complexes of 1-methylthymine and 9-methyladenine, as well as of their complementary pair, have been studied at the RI-MP2/L1 level of theory. The addition of nitrosonium ion to molecules of these compounds or their H-bonded pair gives a set of nitrosonium complexes of different types (1η-3η). The complex with the NO ion coordinated to N of the adenine moiety corresponds to the global minimum on the potential energy surface. The gain in energy in the interaction of nitrosonium complexes of 1-methylthymine and 9-methyladenine with 9-methyladenine and 1-methylthymine, respectively, is larger than in the formation of a neutral 9-methyladenine-1-methylthymine couple. Specific structural features and dynamics of the nitrosonium complexes are discussed. [ABSTRACT FROM AUTHOR]

Dihetaryls containing superelectrophilic and π-excessive heterocycles were synthesized by the nucleophilic aromatic substitution and cycloaddition. The structures of the compounds and the mechanism of 1,3- N-oxide tautomerism were studied by NMR spectroscopy, X-ray diffraction, and quantum chemical methods. The ability of these compounds to initiate SOX induction, which is probably due to the in vivo generation of nitrogen( ii) oxide, was quantified using genetically engineered E. coli-based lux biosensors. 7-(1-Methylpyrrol-3-yl)-4,6-dinitrobenzofuroxan is the most active inducer, which is an order of magnitude more effective than nitroglycerin used as the reference compound. The absence of toxicity was established using the E. coli MG 1655 biosensor (pXen7-lux). The DNA protective effect of this leading compound was confirmed using the E. coli MG 1655 biosensor (pRecA-lux). [ABSTRACT FROM AUTHOR]

By the method RI-MP2/L1 nitrosonium complexes were explored of 1-methylcytosine and 9-methylguanine, structural analogs of nucleotide bases cytosine and guanine, as well as of their complementary pair. The addition of a nitrosonium cation to the molecules of these compounds and to their pair leads to the formation of various types of nitrosonium complexes (1η-3η). n-Complexes with the coordination of NO cation to nitrogen and oxygen atoms are commonly more feasible in energy as compared with π-complexes. The complex with cation NO coordinated at the oxygen atom of the carbonyl group and N atom of the guanine fragment of the pair corresponds to the global minimum on the potential energy surface. The energy gain at the interaction of nitrosonium complexes of 1-methylcytosine and 9-methylguanine with 9-methylguanine and 1-methylcytosine respectively is usually larger than at the formation of a neutral pair 1-methylcytosine-9-methylguanine. [ABSTRACT FROM AUTHOR]

1-Substituted 1 H-1,2-diazaphenalenes (1 H-benzo[ de]cinnolines) undergo nitration with nitric acid leading to the formation of di- and trinitro derivatives. The yield of nitration products depends on nitric acid concentration. [ABSTRACT FROM AUTHOR]

Acylation of 5,7-di( tert-butyl)-2-(5,8-dimethyl-4-piperidinoquinolin-2-yl)-3-(3,5-dimethylphenylamino)tropone leads to the corresponding 3-( N-acetyl- N-arylamino)tropone. Heteronuclear, two-dimensional, and dynamic NMR spectroscopy were used to determine structures of conformers of N-acetyl-3-arylaminotropone. The structure of 3-[ N-acetyl- N(3,5-dimethylphenyl)amino]-5,7-di( tert-butyl)-2-(5,8-dimethyl-4-piperidinoquinolin-2-yl)tropone was established by X-ray diffraction studies. [ABSTRACT FROM AUTHOR]

N-(Carbamoyl)-1-aryl-2,3,4,5,6,7-hexahydro-3-hydroxy-6,6-dimethyl-2,4-dioxo-1 H-indole-3-carboxamides upon dissolution in DMSO or DMF undergo a reversible isomerization to 5-(2-arylamino-4,4-dimethyl-6-oxocyclohex-1-en-1-yl)-5-hydroxypyrimidine-2,4,6(1 H,3 H,5 H)-triones. [ABSTRACT FROM AUTHOR]

A vector model of the multiplet-selective excitation of spin systems by a three-pulse sequence is considered, and, on this basis, a new two-dimensional exchange NMR spectroscopy technique is suggested. This technique provides means to investigate intramolecular and intermolecular chemical and spin exchanges by observing the dynamic behavior of the multiplet pattern of a nucleus that is scalarwise coupled with the unobservable nucleus undergoing exchange. [ABSTRACT FROM AUTHOR]

Tautomeric o-formylbenzoic acid reacts in the aldehyde form with 2-aminopyrrole derivatives to give Schiff bases. The bases upon heating in acetic anhydride smoothly cyclize to 3-acetoxyisoindolin-1-ones with the pyrrole substituents at position 2, which exhibit atropisomerism. [ABSTRACT FROM AUTHOR]

N-Amination of 1-amino(alkylamino, benzylidenamino)-substituted 2-amino- and 2-methylbenzimid-azoles with O-picrylhydroxylamine gave the respective 1,2,3-triamino- and 1,3-diamino-2-methylbenz-imidazolium salts, which cyclized upon treatment with acetic anhydride/KCO into previously unreported derivatives of N-amino[1, 2, 4]triazolo[1,5-а]benzimidazoles and N-aminopyrazolo-[1,5-а]benzimidazoles. The presence of С-acetyl substituent in the formed pyrazolo[1,5-а]benz-imidazoles was interpreted by quantum-chemical calculations as resulting from acylation of the intermediate methylene base, not tricyclic system. [ABSTRACT FROM AUTHOR]