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1.
Alkylation of Pyridines at Their 4‐Positions with Styrenes plus Yttrium Reagent or Benzyl Grignard Reagents
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Tomoya Mizumori Prof. Dr. Takeshi Hata Prof. Dr. Hirokazu Urabe 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(1):422-426
A new regioselective alkylation of pyridines at their 4‐position was achieved with styrenes in the presence of yttrium trichloride, BuLi, and diisobutylaluminium hydride (DIBAL‐H) in THF. Alternatively, similar products were more simply prepared from pyridines and benzyl Grignard reagents. These reactions are not only a useful preparation of 4‐substituted pyridines but are also complementary to other relevant reactions usually giving 2‐substituted pyridines. 相似文献
2.
An efficient one-pot synthesis of isoquinolines and heterocycle-fused pyridines by three-component reaction of aryl ketones, hydroxylamine, and alkynes is developed. The reaction involves condensation of aryl ketones and hydroxylamine, rhodium(III)-catalyzed C-H bond activation of the in situ generated aryl ketone oximes, and cyclization with internal alkynes. This protocol enables rapid assembly of multisubstituted isoquinolines as well as γ-carbolines, furo[2,3-c]pyridines, thieno[2,3-c]pyridines, and benzofuro[2,3-c]pyridines from readily available substrates. 相似文献
3.
Méry D Plault L Ornelas C Ruiz J Nlate S Astruc D Blais JC Rodrigues J Cordier S Kirakci K Perrin C 《Inorganic chemistry》2006,45(3):1156-1167
Hexasubstitution of apical triflate ligands in the octahedral clusters [M]2[Mo6X8(CF3SO3)6] (M = n-Bu4N or Cs, X = Br or I) and monosubstitution in [n-Bu4N]2[Mo6Br13(CF3SO3)] was carried out in tetrahydrofuran at 60 degrees C with simple pyridines and then extended to organometallic pyridines, yielding cluster-cored stars, and to dendronic polyallyl- and polyferrocenylpyridines, yielding cluster-cored polyallyl and polyferrocenyl dendrimers and dendrons. The orange pyridine-substituted clusters, whose pyridine protons are deshielded in 1H NMR (a practical tool for characterization), are air-stable and thermally stable with simple pyridines, light- and air-sensitive with organometallic pyridines, and air-fragile and thermally fragile with large dendronized pyridines. 相似文献
4.
2-,3-和4-溴甲基吡啶的水解反应的动力学研究 总被引:1,自引:0,他引:1
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SN1和SN2. 相似文献
5.
《Tetrahedron》1986,42(8):2253-2262
These are new examples of the homotransmetalation reaction. Instead of the ordinary bromo-metal exchange it is possible to obtain selectively from the 2-bromo 3-fluoro or 2-bromo 3-chloro pyridines the 2-bromo 3-halogeno 4-lithio pyridines, which is very interesting for synthetic utility. From the 4-bromo 3-halogeno pyridines, we can see an isomerization with an halogen dance mechanism and we obtain the 5-bromo 3-halogeno 4-lithio pyridines. In the case of the 2-bromo 3-fluoro pyridine we explain a telesubstitution of bromine from 2 to 4 by a transistory homotransmetalation reaction during the Li-Br exchange. 相似文献
6.
Diethoxymethyl acetate was used to cyclize o-disubstituted aminopyridines to oxazolo[4,5-c]pyridines and imidazo[4,5-c]pyridines. All the possible imidazole-methylated imidazo[4,5-c]pyridines were prepared. A novel synthesis of 2-substituted thiazolo[5,4-c]pyridines and 4-amino-3-pyridinethiol was discovered. 相似文献
7.
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. 相似文献
8.
A new three-component reaction of chalcones, ketones, and ammonia assisted by magnesium methoxide is described. The corresponding 2,4,6-triaryl pyridines (Kröhnke pyridines) are formed in fair to good yields (34–76%) within 3 h. The method also provides a facile way to synthesize 2(6)-difluoromethyl pyridines via an interesting mechanism. 相似文献
9.
Halogenated pyridines I. The synthesis of 3-halogenomethyl pyridines from dimeric acrylonitrile . α-Methyleneglutaronitril, a linear dimerization product of acrylonitrile is a cheap, commercially available starting material for a new synthesis of 3-halogenomethyl-2, 6-dihalogeno- or 2,5,6-trihalogenopyridines prepared in two and three step reactions, respectively. The properties of this new class of halogenated pyridines are discussed. 相似文献
10.
[reaction: see text] 2,3-Disubstituted furo[3,2-b]pyridines, 2,3-disubstituted furo[2,3-b]pyridines, and 2,3-disubstituted furo[2,3-c]pyridines are readily prepared under mild conditions via the palladium-catalyzed cross-coupling of 1-alkynes with o-iodoacetoxy- or o-iodobenzyloxypyridines, followed by electrophilic cyclization by I(2) or by PdCl(2) under a balloon of carbon monoxide. 相似文献
11.
Aymn E. Rashad Ahmed H. Shamroukh Maher A. El‐Hashash Ahmed F. El‐Farargy Nabil M. Yousif Mowafia A. Salama Ahmed Mostafa Mahmoud El‐Shahat 《Journal of heterocyclic chemistry》2012,49(5):1130-1135
Pyridine and fused pyridines derivatives are interesting compounds with diverse chemical properties and pharmacological activities. Herein, the synthesis and antiviral evaluation of some new pyridines are described. 相似文献
12.
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. 相似文献
13.
A. F. Khlebnikov E. I. Kostik R. R. Kostikov 《Chemistry of Heterocyclic Compounds》1991,27(6):636-642
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. 相似文献
14.
Additivity of substituent effects on the proton-proton coupling constants of disubstituted pyridines
From the spin-spin coupling constants of pyridine and monosubstituted pyridines the effects of several substituents have been calculated- Assuming an additivity relationship when two of these substituents are present in the same molecule, the spin-spin coupling constants for 11 disubstituted pyridines have been calculated.The NMR spectra of 13 disubstituted pyridines have been studied to obtain accurate values of their coupling constants. The experimental values of these constants are in very good agreement with those calculated using the additivity relationships. 相似文献
15.
Several Hantzsch 4-alkyl-1,4- dihydropyridines have been oxidized to the corresponding aromatic systems. An unexpected mixture of 4-alkyl pyridines and/or dealkylated pyridines are formed. 相似文献
16.
Some condensed pyridines, isothiazolo[4,5-b]pyridine, 2-oxo-2-thiopyranyl[5,6-b]pyridines, and thieno[3,2-b]pyridines, have been prepared from 3-formyl-2(1)-pyridinethione or the 1-substituted precursors for this compound. 相似文献
17.
Shuntaro Mataka Kazufumi Takahashi Tetsuro Imura Masashi Tashiro 《Journal of heterocyclic chemistry》1982,19(6):1481-1488
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. 相似文献
18.
An additivity relationship for chemical shifts similar to that found in the literature for coupling constants has been tested in eleven disubstituted pyridines. The chemical shifts of these disubstituted pyridines were measured in different solvents at different concentrations and extrapolated to infinite dilution.In order to compute the “effects” of the different substituents, the chemical shifts of the corresponding monosubstituted pyridines and of pyridine were measured in the same solvents at different concentrations. These chemical shifts were extrapolated to infinite dilution.In most cases it was found that the extrapolated chemical shifts for disubstituted pyridines are in good agreement with those calculated using the additivity relationship. Only in a few cases was it found that the additivity scheme does not hold. 相似文献
19.
《Analytical letters》2012,45(7):545-560
Abstract A quantitative analytical method has been developed for volatile pyridines in tobacco smoke using pyridine- 14C as an internal standard. Mainstream and sidestream smoke are trapped in 0.05 N sulfuric acid anti partitioned with chloroform. The acidic portion is then concentrated, adjusted to pH 3 and extracted with chloroform. Methanol and a trace of 2N sulfuric acid are added to this chloroform portion and the mixture is carefully concentrated. A trace of sodium hydroxide is added and the final concentrate is analyzed by gas chromatography. Twenty-one volatile pyridines have been identified. The mainstream stroke of a popular. 85-mm U.S. cigarette without filter tip contained the following major pyridines: 33.4 μg pyridine, 12.3 μg α-picoline, 24.2 μg. β+γ-picoline, 7.6 μg 3-ethylpgridine, 5.9 μg: 4-ethylpyridine, and 23.3 μg 3,4-lutidine + 3-vinylpyridine. The sidestream smoke of this cigarette contained up to 28 times higher concentrations of pyridines. Volatile pyridines were also determined in the mainstream smoke of other non-filter cigarettes, filter cigarettes, little cigars and, a non-tobacco cigarette. Of special interest were the much greater quantities of volatile pyridines in the mainstream and sidestream of cigars in comparison to those of cigarettes. The ratio of pyridines in sidestream to those in mainstream was 5 to 50 in large cigars. Selective filtration was observed with both cellulose acetate and charcoal filter tips. The analytical method resulted in reproducible values for pyridine, with an average recovery rate of more than 90%. In addition to pyridines, two pyrazines were also isolated from the smoke. Processed tobacco contained minute amounts of some volatile pyridines. 相似文献
20.
A concise one-pot synthesis of highly functionalized pyridines has been developed. The first step in the reaction sequence is the formal insertion of rhodium vinylcarbenoids across the N-O bond of isoxazoles. Upon heating, the insertion products undergo a rearrangement to give 1,4-dihydropyridines. DDQ oxidation then affords the corresponding pyridines in 31-84% yield. The process has proven general with a range of carbenoid and isoxazole components and represents a unique disconnection strategy for the synthesis of functionalized pyridines. 相似文献