1,3-Dipolar cycloaddition reactions of 3-acylimino-1-methylbenzimidazolium betaines

3-Acylimino-1-methylbenzimidazolium betaines undergo 1,3-dipolar cycloaddition reactions with activated alkenes (methyl acrylate, acrylonitrile, and fumaronitrile) and methyl propiolate to produce 2-substituted 1-methylbenzimidazoles. The transformation involves the initial formation of a 1,3-dipolar cycloadduct followed by the N? N bond cleavage. The primary adducts can be isolated from the reaction with methyl acrylate and acrylonitrile.     

Synthesis and physico-chemical properties of ionic liquids based on 1-butyl-3-alkylimidazolium with inorganic anions

Ionic liquids with 1-butyl-3-alkylimidazolium (alkyl = C₄H₉, C₈H₁₇, or C₁₀H₂₁) cation and Br^–, BF ₄ ^– , or PF ₆ ^– anions have been obtained. Composition and structure of the compounds have been confirmed by elemental analysis and IR spectroscopy data. Electrical conductivity of solutions of the synthesized compounds in acetonitrile has been studied, and association constant as well as equivalent electrical conductivity at infinite dilution have been calculated. Thermal stability of the prepared ionic liquids in air at 25–500°С has been studied.     

Syntheses, structures and properties of 1-ethyl-3-methylimidazolium salts of fluorocomplex anions

Fluoroacid-base reactions of a room-temperature ionic liquid, 1-ethyl-3-methylimidazolium fluorohydrogenate (EMIm(HF)2.3F, EMIm = 1-ethyl-3-methylimidazolium cation), and Lewis fluoroacids (BF3, PF5, AsF5, NbF5, TaF5 and WF6) give EMIm salts of the corresponding fluorocomplex anions, EMImBF4, EMImPF6, EMImAsF6, EMImNbF6, EMImTaF6 and EMImWF7, respectively. Attempts to prepare EMImVF6 by both the acid-base reaction of EMIm(HF)2.3F with VF5 and the metathesis of EMImCl with KVF6 failed due to the strong oxidizing power of the pentavalent vanadium, whereas EMImSbF6 was successfully prepared only by the metathesis of EMImCl and KSbF6. EMImBF4, EMImSbF6, EMImNbF6, EMImTaF6 and EMImWF7 are liquids at room temperature whereas EMImPF6 and EMImAsF6 melts at around 330 K. Raman spectra of the obtained salts showed the existence of the EMIm cation and corresponding fluorocomplex anions. IR spectroscopy revealed that strong hydrogen bonds are not observed in these salts. EMImAsF6(mp 326 K) and EMImSbF6(mp 283 K) are isostructural with the previously reported EMImPF6. The melting point of the hexafluorocomplex EMIm salt decreases with the increase of the size of the anion (PF6- < AsF6- < SbF6- 相似文献   

Syntheses, pi-stacking interactions and base-pairings of uracil pyridinium salts and uracilyl betaines with nucleobases

Reaction of 6-chlorouracil with 4-(dimethylamino)pyridine, 4-methylpyridine, and pyridin-4-yl-morpholine yielded pyridinium-substituted uracils as chlorides which were converted into pyridinium uracilates by deprotonation. These heterocyclic mesomeric betaines are cross-conjugated and thus possess separate cationic (pyridinium) and anionic (uracilate) moieties. Calculations and X-ray single crystal analyses were performed in order to characterize these systems and to compare the salts with the betaines. (1)H NMR experiments in D(2)O proved pi-interactions between the uracilyl betaines and adenine, adenosine, as well as adeninium. No pi-stacking interactions were detected between the betaines and guanosine. The acidic N8-H group of the uracil pyridinium salts caused acid-base reactions which were observed in parallel to pi-stacking interactions. Self-complementarity of the modified uracils was detected by (1)H NMR experiments in DMSO-d(6) and electrospray ionisation mass spectrometry (ESIMS). Ab initio calculations predicted base-pairings of the modified uracils with adeninium, cytosine, and guanine. Several geometries of hydrogen-bonded associates were calculated. Hoogsteen pairings between the uracil-4-(dimethylamino)pyridinium salt and adeninium, as well as associates between the corresponding betaine plus cytosine, and the betaine plus guanine were calculated, and the most stable conformations were determined. In the ESI mass spectra, prominent peaks of associates between the modified uracils and adeninium, cytosine, cytidine, guanosine and d(CpGp) were detected.     

Mesomeric betaines of azolium azolate: Synthesis and properties

A facile entry into the almost unknown azolium azolate inner salts is described, and the structure of these highly dipolar compounds is well reflected by their spectroscopic properties and reactivity towards electrophiles (MeI) and dipolarophiles (DMAD) under mild conditions.     

Pseudo-cross-conjugated mesomeric betaines. 1. Synthesis of pseudo-cross-conjugated mesomeric betaines from quinoxaline derivatives

A new method for the synthesis of pseudo-cross-conjugated mesomeric betainic heterocyclic compounds with an angular nitrogen atom has been developed consisting in the reaction of 1,4-dielectrophile — -carbethoxy-2-(3-chloro)quinoxalylacetonitrile with azoles. Experimental regularities have been studied and a reaction mechanism has been proposed including the stage of formation of an ylide from a quaternary azolium salt. A pseudo-crossconjugated mesomeric betainic heterocyclic compound containing a thiazole ring compound has been synthesized for the first time.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1528–1533, November, 1992.     

Syntheses of 1-substituted-3-aminopyrazoles

A series of 1-substituted-3-aminopyrazoles were prepared via Chan-Lam coupling reactions, alkylation, and pyrazole ring formation.     

Preparation and properties of betaines of 4-pyridyl-3,4-dihydropyridine-2-thiones(1H)

Condensation of 2-cyano-3-pyridylthioacrylamides with esters of acetoacetic or -aminocrotonic acids yields betaines of 3,5,6-substituted-4-pyridyl-3,4-dihydropyridine-2-thiones(1H). The spectral characteristics of the betaines have been examined and their ionization constants (pK) determined.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 630–635, May, 1986.     

Structure and photochromic properties of the crystalline 1,3-dimethyl-2-(3-phenylnorbornadienyl)benzimidazolium tetrafluoroborate

Molecular and crystal structures, as well as photochemistry in the solid state were studied for the norbornadiene, whose one double bond was modified by the simultaneous introduction of an electron-donating and electron-withdrawing substituents. Effects of the nature of substituents on the distance of the substituted C=C bond were analyzed by quantum chemical calculations.     

Syntheses and properties of chiral pentahomothiazacalix[3]arenes

Chiral calixarene analogs incorporating an aminoethanethiol unit such as L-cysteine into their rings were prepared. Conformational analysis of the macrocycles by using ¹H and ¹³C nmr spectroscopy revealed that their preferred conformation was a cone, which was more stable in chloroform than in toluene. The introduction of an aminoethanethiol moiety into the macrocyclic ring caused ring fluctuation, however, the carboxylic acid derivative was a highly rigid structure in the cone form. The ¹H nmr and circular dichroism spectra of the macrocycles showed the existence of chirality of the phenol-formaldehyde unit, which was induced by the chirality of the cysteine moiety.     

Syntheses and properties of benzodipyrrinones

2,3‐Benzannelated dipyrrinone analogs ( 1 and 2 ) of xanthobilirubic acid ( 3 ) are prepared by base‐catalyzed condensation of isoindolinone ( 5 ) and indolin‐2‐one ( 6 ) respectively, with methyl 3‐(2‐formyl‐3,5‐dimethyl‐1H‐pyrrol‐4‐yl)propanoate ( 4 ). Nuclear Overhauser effect H‐nmr studies indicate that both 1 and 2 adopt preferentially a syn‐Z configuration. The former forms a hydrogen‐bonded homodimer in nonpolar solvents; the latter is intramolecularly hydrogen bonded.     

Synthesis and properties of dipyridinium betaines of derivatives of 1,4-benzoquinone and tetracyanoquinodimethane

Reaction of chloranil with excess pyridine gives the poorly stable 2,5-di(N-pyridinium)-3,6-dichloro-1,4-benzoquinone dichloride which is readily hydrolyzed to give the bisbetaine of 2,5-di(N-pyridinium)-1,4-benzoquinone-3,6-dioxide. Treatment with acid gives its mono- and bisprotonated derivatives as the perchlorate and dibromide and bromination gives the betaine 2-bromo-2,5-di(N-pyridinium)-5-cyclohexene-1,3,4-trione-6-oxide perbromide. The reaction of malonodinitrile with 2,5-di(N-pyridinium)-3,6-dichloro-1,4-benzoquinone dichloride in situ gives the poorly stable bisbetaine of 2,5-di(N-pyridinium)-7,7,8,8-tetracyanoquinodimethane-3,6-dioxide.Riga Technical University, Riga LV-1048. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 346–349, March, 1998.     

Syntheses,structures and properties of complexes of indole-3-propionic acid

Three complexes [Zn₂(IPA)₂(phen)₄](HIPA)₂(NO₃)₂·H₂O (1), {[Zn(IPA)₂(bipy)]·3H₂O}_n (2), and {[Mn(IPA)₂(bipy)(H₂O)]·2H₂O}_n (3) (HIPA = indole-3-propionic acid, phen = 1,10-phenanthroline, bipy = 4,4′-bipyridine) were synthesized and characterized by physico-chemical and spectroscopic methods. Complex 1 displays a zero-dimensional structure, whilst 2 and 3 show one-dimensional chains, which are linked into supramolecular networks through hydrogen bonding interactions and/or π···π stacking interactions. The luminescence properties of complexes 1 and 2 were investigated.     

Syntheses, characterization and fluorescent properties of two triethylene-glycol dicoumarin-3-carboxylates

Two novel triethylene-glycol dicoumarin-3-carboxylates were synthesized and characterized by element analysis, (1)H NMR, FT-IR and UV-vis absorption spectra. The photoluminescent behaviors of triethylene-glycol dibenzo[5,6]coumarin-3-carboxylate doped in PMMA were discussed. These compounds exhibit strong blue emission under ultraviolet light excitation. Compared to coumarin-3-triethylene glycol diester, the absorption and emission spectra of benzo[5,6]coumarin-3-triethylene glycol diester was bathochromically shifted due to the larger conjugation of benzene moiety. These derivatives have potential possible to explore organic electroluminescent materials.     

Syntheses and photophysical properties of fluorescent 2-aryl-3-hydroxy-4-chromenones

The particle detectors proposed for the Super-conducting Super Collider contain polystyrene scintillation fibers as a component. Scintillation fluors soluble in styrene are required which have improved light output and response time. New 2-aryl-3-hydroxy-4-chromenones related to 3-hydroxyflavone were prepared which displayed these improved properties. Improved solvent systems for chromenone formation were essential in the synthesis of two of the chromenones. One chromenone produced fluorescence emission at 560 nm with a quantum yield of 0.53 and a scintillation decay time of 5 nsec.