Functionalized sulfur-containing compounds. 13. Synthesis of substituted 3-amino-2-(organylsulfinyl)-and-(organylsulfonyl)thieno[2,3-b]pyridines

A method for the synthesis of substituted 3-amino-2-(organylsulfinyl)thieno[2,3-b]pyridines by the Thorpe—Ziegler intramolecular cyclization of substituted 3-cyano-2-[(organyl-sulfinyl)methylthio]pyridines was proposed. 3-Amino-2-(organylsulfonyl)thieno[2,3-b]pyridines were obtained by reactions of substituted 3-cyanopyridine-2-thiones with chloromethyl organyl sulfones. The reaction intermediates 3-cyano-2-[(organylsulfonyl)methylthio]pyridines were transformed into 3-amino-2-(organylsulfonyl)thieno[2,3-b]pyridines. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 510–515, March, 2006.     

2-,3-和4-溴甲基吡啶的水解反应的动力学研究

用HPLC测定了2-、3-和4-溴甲基吡啶在60℃、离子强度μ为0.15、pH 0.9～9.9的缓冲溶液中水解成相应的羟甲基吡啶的反应速度.通过数学处理,求得溴甲基吡啶的一级和二级反应速度常数以及溴甲基吡啶共轭酸的一级反应速度常数.水解反应的可能机理是S_N1和S_N2.     

Reduction of 4,7-diphenyl-1,2,5-thia(oxa)diazolo[3,4-c]pyridines affording 2,5-diphenyl-3,4-diaminopyridines and ring closure of the diamines to fluorescent azaheterocycles

Reduction of 4,7-diphenyl-1,2,5-thia- ( 1a-i ) and 1,2,5-oxadiazolo[3,4-c]pyridines ( 3a and c-e ) gave 3,4-diamino-2,5-diphenylpyridines ( 2a-g ), which were converted into the fluorescent triazolo[4,5-c]-( 5 ), 1,2,5-selenadiazolo[3,4-c]- ( 6 ), imidazolo[4,5-c]pyridines ( 8 ), and pyrido[5,6-c]pyridines ( 11 ). In the reduction of 3a, c and e , 4,5-dihydro[1,2,5]oxadiazolo[3,4-c]pyridines ( 4a-c ) were obtained.     

Synthesis of vinylsulfonyl(halo)pyridines and their reactions with binucleophilic reagents

Oxidation of vinylthio(halo)pyridines with 30–33% hydrogen peroxide solution in acetic anhydride at 20–25°C furnished vinylsulfonyl(halo)pyridines. Nucleophilic addition reactions of 2-amino-1-ethanethio hydrochloride and thiosemicarbazide to the multiple bonds of vinylsulfonyl(halo)pyridines were performed.Translated from Zhurnal Organicheskoi Khimii, Vol. 40, No. 11, 2004, pp. 1705–1708.Original Russian Text Copyright © 2004 by Amosova, Gavrilova.     

Synthesis,characterization and antioxidant activity of bis (arylsulfonylmethyl/arylaminosulfonylmethylazolyl) pyridines

A new class of bis(arylsulfonylmethylazolyl)pyridines and bis(arylaminosulfonylmethyl-azolyl)pyridines were synthesized from the synthetic intermediates methyl arylsulfonylacetic acid hydrazide and methyl arylaminosulfonylacetic acid hydrazide adopting a green methodology-ultrasonication. All the synthesized compounds were resulted in higher yield and in shorter reaction times. The spectral parameters such as IR, ¹H NMR, ¹³C NMR, mass and microanalyzes were used to determine the structures of all the synthesized compounds and were assayed for antioxidant activity. The bis(arylaminosulfonylmethylazolyl)pyridines showed higher radical scavenging activity than the bis(arylsulfonylmethylazolyl)pyridines. Besides, unsubstituted, and methyl substituted compounds exhibited greater activity. Among all the tested compounds 8b and 11b were identified as potential antioxidants.     

Ein biologischer Vergleich zwischen Benzol und Pyridin in kondensierten Ringsystemen

The synthesis of imidazo[4,5-b]pyridines and of [1,2,4]-triazolo[1,5-a]pyridines is described, and their biological activity in relation to the standard antiviral substance, 2-(α-hydroxybenzyl)benzimidazol, is discussed.     

One-pot,three-component synthesis of 1-amidomethyl-imidazo[1,2-a]pyridines catalyzed by ytterbium triflate

A straightforward method has been developed for the synthesis of 1-amidomethyl-imidazo[1,2-a]pyridines by Yb(OTf)₃ catalyzed three-component reaction of aldehydes, acetamide, and imidazo[1,2-a]pyridines. A series of substituted 3-substituted imidazo[1,2-a]pyridines were synthesized in moderate to good yield (21–74%) under mild reaction condition and the catalyst was recycled for four cycles.     

Transition‐Metal‐Free BF3‐Mediated Oxidative and Non‐Oxidative Cross‐Coupling of Pyridines

We report a BF₃‐mediated direct alkynylation of pyridines at C(2) by using a variety of alkynyllithium reagents (oxidative cross‐coupling). Moreover, we have developed a novel transition‐metal‐free cross‐coupling method between alkylmagnesium reagents and 4‐substituted pyridines, such as isonicotinonitrile and 4‐chloropyridine, by employing BF₃?OEt₂ as a promoter. The combination of these methods enabled us to efficiently prepare a range of di‐, tri‐, and tetrasubstituted pyridines.     

The reactions of some halogenated pyridines with methoxide and methanethiolate ions in dimethylformamide

The reactions of 2,6- and 2,5-dibromopyridines and of 2,3- and 3,5-dichloropyridines with sodium isopropanethiolate and methanethiolate afforded the products of mono- or of bis-substitution depending on the experimental conditions. The same pyridines reacted with sodium methoxide to give good yields of the mono-substituted products; bis-substitution occurred easily only in the case of the 2,6-dibromo- and of the 3,5-dichloropyridine. The syntheses of some methoxy thiomethoxypyridine, starting from the halogeno methoxypyridines or from the halogeno thiomethoxypyhdines are also described. The bis-(alkylthio)pyridines can be fragmented by sodium in HMPA to give the bis(mercapto)pyridines.     

NMR and theoretical study on interactions between diperoxovanadate complex and 4-substituted pyridines

To understand the substituting group effects of organic ligands on the reaction equilibrium, the interactions between diperoxovanadate complex [OV(O2)2(D2O)]-/[OV(O2)2(HOD)](-) and a series of 4-substituted pyridines in solution were explored using multinuclear (1H, 13C, and 51V) magnetic resonance, DOSY, and variable temperature NMR in 0.15 mol/L NaCl ionic medium for mimicking the physiological condition. Some direct NMR data are given for the first time. The reactivity among the 4-substituted pyridines is pyridine > isonicotinate > N-methyl isonicotinamide > methyl isonicotinate. The competitive coordination results in the formation of a series of new six-coordinated peroxovanadate species [OV(O2)2L](n-) (L = 4-substituted pyridines, n = 1 or 2). The results of density functional calculations provide a reasonable explanation on the relative reactivity of the 4-substituted pyridines. Solvation effects play an important role in these reactions.     

Reaction of dihalocarbenes with 2-(benzylideneamino)pyridines. Cyclization of 2-(benzylideneamino)pyridinium dihalomethylids to give 2-aryl-3-haloimidazo[1,2-α]pyridines

Pyridinium dichloromethylids, formed in the reaction of dichlorocarbene with 2-(benzylideneamino)pyridines, undergo intramolecular 1,5-cyclization to give 2-aryl-3-chloroimidazo[1,2-a]pyridines, which undergo partial conversion to 2-aryl-3-chloro-4H-pyrido[1,2-a]pyrimidin-4-ones under the reaction conditions. 2-Aryl-3-bromoimidazo[1,2-a]pyridines and 2-[N-(1-aryl-2,2,2-tribromoethyl)amino]pyridines, respectively, are obtained in the reaction of dibromocarbene and the tribromomethyl onion generated in the reaction of bromoform with potassium hydroxide.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 810–816, June, 1991.     

Convenient synthesis of 4-amino-7-(dialkylamino)pyrido[2,3-d]pyrimidines from polysubstituted pyridines

A convenient synthesis of 4-amino-7-(dialkylamino)pyrido[2,3-d]pyrimidines via cyclization of functionalized pyridines is reported. The preparation of the starting pyridines from 3-amino-3-(dialkylaraino)propene-nitriles and ethoxymethylenemalononitrile is described.     

A Facile synthesis of 3-alkylthio-(or arylthio-)pyridines and 3,5-bis(alkylthio)pyridines

3-Alkylthio- (or 3-arylthio-)pyridines and 3,5-bis(alkylthio)pyridine can be conveniently prepared by the reaction of 3-thiocyanato- or 3,5-bis(thiocyanato)pyridines with tri-n-butylphosphine in the presence of alcohol.     

Investigation of B ⋯ HA ⇌ B+H ⋯ A− equilibrium in complexes of trifluoroacetic acid with pyridines in dichloromethane by second derivative infrared spectroscopy

The second derivative of FTIR spectra in the carbonyl—carboxyl region has been used in order to study the interaction of trifluoroacetic acid with eight R-pyridines in dichloromethane. In the case of the equimolar base—acid mixture, the following species (a) B · HA, (b) B · HA · HA, (c) B⁺H · A⁻ and (d) B⁺H · A⁻ · HA are recognized. All of the species are present in complexes of the medium strong pyridines (R = H or D, 3-Me and 4-Me). Two species (a) and (b) are found for complexes of the weakest, when R = 4-CN and 3-Br, and another two (c) and (d) for complexes of the strongest, when R = 3-NMe₂ and 2,4,6-Me₃, pyridines. Complete formation of the 1:1 complex requires an excess of pyridines. Fermi resonance of overtones due to pyridines and the acid with the continuous absorption is observed.     

Facile synthesis of benzo[4,5]furo[3,2-c]pyridines via palladium-catalyzed intramolecular Heck reaction

The heating of 4-chloropyridine with 2-bromophenol in either neat or DME as solvent gives rise to 2-bromophenoxy pyridines, which were treated with Pd(OAc)₂ and various ligands to afford functionalized benzo[4,5]furo[3,2-c]pyridines.     

Pyridinethiones—II : Preparation of condensed pyridines related to 3-formyl-2(1H,-pyridinethione

Some condensed pyridines, isothiazolo[4,5-b]pyridine, 2-oxo-2$\text{H}$-thiopyranyl[5,6-b]pyridines, and thieno[3,2-b]pyridines, have been prepared from 3-formyl-2(1$\text{H}$)-pyridinethione or the 1-substituted precursors for this compound.     

1-Alkynyl- and 1-alkenyl-3-arylimidazo[1,5-a]pyridines: synthesis, photophysical properties, and observation of a linear correlation between the fluorescent wavelength and Hammett substituent constants

1-Alkynyl- and 1-alkenyl-3-arylimidazo[1,5-a]pyridines were synthesized. The Sonogashira coupling of 3-aryl-1-iodoimidazo[1,5-a]pyridines and various terminal alkynes with Pd(PPh(3))(2)Cl(2) (10 mol %) and CuI (10 mol %) in triethylamine at 80 °C for 12 h afforded the corresponding 1-alkenyl-3-arylimidazo[1,5-a]pyridines in good to excellent yields. The Mizoroki-Heck reaction of 3-aryl-1-iodoimidazo[1,5-a]pyridines and various styrene derivatives proceeded smoothly with Pd(OAc)(2) (5 mol %), IMes·HCl (10 mol %), and Cs(2)CO(3) (2 equiv) in DMA at 130 °C for 20 h to give the alkenylated imidazo[1,5-a]pyridines in moderate to high yields. The fluorescence maxima and fluorescence quantum yields of the alkynylated products were 458-560 nm and Φ(F) = 0.08-0.26 in chloroform solution, and those of the alkenylated imidazopyridines were 479-537 nm and Φ(F) = 0.03-0.13. The absorption behaviors of the obtained alkynylated and alkenylated imidazo[1,5-a]pyridines showed a good fit to the values predicted by TDDFT calculations at the B3LYP/6-311++G(d,p) level. In addition, the alkynylated imidazo[1,5-a]pyridines obtained showed linear correlations between the Hammett substituent constants of the substituents on the arylalkynyl group and their fluorescence wavelengths.     

Facile one‐pot syntheses of new polyfunctional pyrazolyl substituted and pyrazolofused pyridines

Ethyl 2‐cyano‐3‐(5‐chloro‐1,3‐diphenylpyrazol‐4‐yl)acrylate ( 1 ) undergoes both conjugate addition of a number of methylene‐active ethanenitriles and direct addition of other active methylene donors to the cyano carbon atom. These additions are the starting events of cascades of subsequent reactions eventually forming (i) novel polyfunctional pyrazolyl‐substituted monocyclic pyridines ( 4a , b and 6 ), (ii) 1,3‐benzothiazole and benzimidazole‐fused pyridines ( 11, 13 ) and (iii) pyrazolo[5,4‐b]pyridines ( 19b, 20 ) in one‐pot reactions in ethanolic solution containing catalytic amounts of piperidine.     

Acid-catalyzed reactions of 3-(hydroxymethyl)- and 3-(1-hydroxyethyl)pyrazolo[1,5-a]pyridines

Treatment of 3-(hydroxymethyl)pyrazolo[1,5-a]pyridines with trifluoroacetic acid in refluxing dichloro-methane led to the formation of bis(pyrazolo[1,5-a]pyrid-3-yl)methanes or bis[(pyrazolo[1,5-a]pyrid-3-yl)]-methyl ethers depending upon the concentration of trifluoroacetic acid. In contrast, similar treatment of 3-(1-hydroxyethyl)pyrazolo[1,5-a]pyridines gave a mixture of 3-vinylpyrazolo[1,5-a]pyridines and 1,3-bis(pyrazolo-[1,5-a]pyrid-3-yl)-1-butenes.     

Alkyl-substituted 2,6-dioxadiazolylpyridines as selective extractants for trivalent actinides

2,6-di(3-alkyl-1,2,4-oxadiazol-5-yl)pyridines, 2,6-di(5-alkyl-1,3,4-oxadiazol-2-yl)pyridines, and 2,6-di(5-alkyl-1,2,4-oxadiazol-3-yl)pyridines were synthesized and tested for their americium(III)-europium(III) selectivity by liquid-liquid extraction. 0.02M solutions of the compounds extract americium(III) 2-bromohexanoates as monosolvates, AmA₃B, from solutions of pH 2, with an americium(III)-europium(III) separation factor of up to 23. Decreasing the alkyl chain length (butyl < ethyl < methyl) or the polarity of the diluent (chlorobenzene < toluene < tert.-butyl benzene) increased both americium(III) distribution ratio and americium(III)-europium(III) separation factor.