- A Porous Organic Polymer Nanotrap for Efficient Extraction of Palladium
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To offset the environmental impact of platinum-group element (PGE) mining, recycling techniques are being explored. Porous organic polymers (POPs) have shown significant promise owing to their selectivity and ability to withstand harsh conditions. A series of pyridine-based POP nanotraps, POP-Py, POP-pNH2-Py, and POP-oNH2-Py, have been designed and systematically explored for the capture of palladium, one of the most utilized PGEs. All of the POP nanotraps demonstrated record uptakes and rapid capture, with the amino group shown to be vital in improving performance. Further testing on the POP nanotrap regeneration and selectivity found that POP-oNH2-Py outperformed POP-pNH2-Py. Single-crystal X-ray analysis indicated that POP-oNH2-Py provided a stronger complex compared to POP-pNH2-Py owing to the intramolecular hydrogen bonding between the amino group and coordinated chlorine molecules. These results demonstrate how slight modifications to adsorbents can maximize their performance.
- Aguila, Briana,Al-Enizic, Abdullah M.,Cassady, Harper C.,Liang, Zhiqiang,Ma, Shengqian,Meulenberg, Robert W.,Nafadyc, Ayman,Shan, Chuan,Sun, Qi,Wright, Joshua T.
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Read Online
- Directing Group Enables Electrochemical Selectively Meta-Bromination of Pyridines under Mild Conditions
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Without the use of catalysts and oxidants, a facile and sustainable electrochemical bromination protocol was developed. By introducing the directing groups, the regioselectivity of pyridine derivatives could be controlled at themeta-position utilizing the inexpensive and safe bromine salts at room temperature. A variety of brominated pyridine derivatives were obtained in 28-95% yields, and the reaction could be readily performed at a gram scale. By combining the installation and removing the directing group, the concept ofmeta-bromination of pyridines could be verified.
- Wu, Yanwei,Xu, Shanghui,Wang, Hong,Shao, Dongxu,Qi, Qiqi,Lu, Yi,Ma, Li,Zhou, Jianhua,Hu, Wei,Gao, Wei,Chen, Jianbin
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p. 16144 - 16150
(2021/07/19)
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- Novel synthesis method of crizotinib intermediate (by machine translation)
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The invention relates to a synthesis method of an organic compound, in particular to a novel synthesis method of a crizotinib intermediate, which comprises the following steps: taking cheap and easily available 2,6 - dichloro -3 - fluoroacetophenone as a starting raw material and reducing the CBS system to obtain S-shaped chiral alcohol. , 2 - Aminopyridine is taken as a raw material and bromine is brominated to obtain 3,5 - dibromo -2 - aminopyridine. The compound is condensed into an ether with a chiral alcohol under the action of an acid-binding agent to obtain the intermediate of the required configuration. The method is simple in reaction, short in route, less in three wastes, environment-friendly, high in yield of all steps, and less in raw material and reagent waste. (by machine translation)
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Paragraph 0024
(2021/01/04)
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- Optimizing the performance of porous pyridinium frameworks for carbon dioxide transformation
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Multifunctional catalysts derived from the integration of discrete catalytic partners in a confined space represent an important approach to emulate some of the design philosophies of enzymes. In an effort to design concepts for highly active catalysts for CO2 transformations, we synthesize and contrast the performance of two porous pyridinium frameworks. The activity is found to be significantly amplified by the introduction of the amine group on the ortho position of the pyridinium moieties. The resulting catalyst is capable of highly active and selective cycloaddition of aziridines with CO2 to 5-substituted-2-oxazolidinone, even under ambient conditions (1 bar, 22 °C). Its high activity originates from CO2 activation by the pendant amine group in the vicinity of the active species, which facilitates the subsequent catalytic steps.
- Song, Yanpei,Sun, Qi,Aguila, Briana,Ma, Shengqian
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p. 557 - 562
(2020/02/13)
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- Preparation method of 2-amino substituted six-membered nitrogen-containing heterocycle complex
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The invention discloses a preparation method of a 2-amino substituted six-membered nitrogen-containing heterocycle complex. The preparation method comprises the following steps: mix 2-fluorine substituted six-membered nitrogen-containing heterocycle complex and amidine hydrochloride salt compound, and then react under the action of a alkaline substance to obtain a 2-amino substituted six-memberednitrogen-containing heterocycle complex. Preferably, the 2-amino substituted six-membered nitrogen-containing heterocycle complex is a 2-amino pyridine compound, a 2-aminopyrimidine compound or a 2-aminopyrazine compound. Compared with the prior art, the method has the advantages of simple synthesis conditions, less reaction steps, mild reaction conditions, low cost of the catalyst used, less waste discharge and good functional group tolerance.
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Paragraph 0025; 0026; 0087
(2019/02/08)
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- AMINATION AND HYDROXYLATION OF ARYLMETAL COMPOUNDS
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In one aspect, the present disclosure provides methods of preparing a primary or secondary amine and hydroxylated aromatic compounds. In some embodiments, the aromatic compound may be unsubstituted, substituted, or contain one or more heteroatoms within the rings of the aromatic compound. The methods described herein may be carried out without the need for transition metal catalysts or harsh reaction conditions.
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Paragraph 0257
(2018/03/25)
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- Transition-metal-free access to 2-aminopyridine derivatives from 2-fluoropyridine and acetamidine hydrochloride
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Under catalyst-free conditions, an efficient method for the synthesis of 2-aminopyridine derivatives through the nucleophilic substitution and hydrolysis of 2-fluoropyridine and acetamidine hydrochloride has been developed. This amination uses inexpensive acetamidine hydrochloride as the ammonia source and has the advantages of a high yield, high chemoselectivity and wide substrate adaptability. The results suggest that other N-heterocycles containing fluorine substituents can also complete the reaction via these reaction conditions and yield the target products.
- Li, Yibiao,Huang, Shuo,Liao, Chunshu,Shao, Yan,Chen, Lu
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supporting information
p. 7564 - 7567
(2018/11/02)
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- Handling Hydrogen Peroxide Oxidations on a Large Scale: Synthesis of 5-Bromo-2-nitropyridine
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5-Bromo-2-nitropyridine was prepared from the corresponding amine via hydrogen peroxide oxidation in large scale production. This transformation initially showed low conversion, high impurity content and lack of reproducibility in lab trials. Parallel to process development, safety studies were conducted to investigate the stability of oxidant mixture, its composition and the oxidation reaction itself by reaction and adiabatic calorimetry. The resulting robust reaction conditions and appropriate safety boundaries allowed to develop a reproducible, safe protocol for the implementation of this chemistry on large scale, obtaining consistent results throughout the campaign.
- Agosti, Alessandro,Bertolini, Giorgio,Bruno, Giacomo,Lautz, Christian,Glarner, Thomas,Deichtmann, Walter
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p. 451 - 459
(2017/03/24)
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- Non-deprotonative primary and secondary amination of (hetero)arylmetals
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Herein we disclose a novel method for the facile transfer of primary (-NH2) and secondary amino groups (-NHR) to heteroaryl-as well as arylcuprates at low temperature without the need for precious metal catalysts, ligands, excess reagents, protecting and/or Erecting groups. This one-pot transformation allows unprecedented functional group tolerance and it is wellsuited for the amination of electron-rich, electron-deficient as well as structurally complex (hetero)arylmetals. In some of the cases, only catalytic amounts of a copper (l) salt is required.
- Zhou, Zhe,Ma, Zhiwei,Behnke, Nicole Erin,Gao, Hongyin,Kürti, László
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supporting information
p. 115 - 118
(2017/05/16)
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- Synthesis and evaluation of the anticoccidial activity of trifluoropyrido[1,2-a]pyrimidin-2-one derivatives
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Screening of our chemical library to discover new molecules exhibiting in vitro activity against the invasion of host cells by Eimeria tenella revealed a lead compound with an IC50 of 15 μM. Structure-activity relationship studies were conducted with 34 newly synthesized compounds to identify more active molecules and enhance in vitro activity against the parasite. Four compounds were more effective in inhibiting MDBK cell invasion in vitro than the lead compound.
- Silpa, Laurence,Niepceron, Alisson,Laurent, Fabrice,Brossier, Fabien,Pénichon, Mélanie,Enguehard-Gueiffier, Cécile,Abarbri, Mohamed,Silvestre, Anne,Petrignet, Julien
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supporting information
p. 114 - 120
(2015/12/18)
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- Preparation of 2,3-Disubstituted 5-Bromo-1 H -pyrrolo[2,3- b ]pyridine Framework by Fischer Cyclization
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A simple synthesis of some hard-to-reach heterocycles containing 2,3-disubstituted 5-bromo-1H-pyrrolo[2,3-b]pyridine framework by FisNher indole cyclization in polyphosphoric acid has been developed. A particularly valuable feature of this synthetic route is the possibility to build a 5-bromo-7-azaindole scaffold with alkyl or aryl substituents at positions 2 and 3 from available starting materials.
- Alekseyev, Roman S.,Amirova, Sabina R.,Terenin, Vladimir I.
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p. 3169 - 3178
(2015/10/19)
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- A mild method for the regioselective bromination of 2-aminopyridines
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An efficient and regioselective bromination of 2-aminopyridines was developed. The environmental friendly bromination occurs under mild and clean conditions using readily available 1-butylpyridinium bromide as the bromine source and hydrogen peroxide as the green oxidant.
- Xu, Tong,Zhou, Wen,Wang, Jing,Li, Xue,Guo, Jun-Wen,Wang, Bin
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supporting information
p. 5058 - 5061
(2015/01/08)
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- Bromination of arenes using I2O5-KBr in water
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An efficient and environmentally benign bromination of various aromatic compounds using aN aqueous I2O5-KBr system at room temperature has been developed in this work. A series of aromatic compounds such as acetophenones, benzaldehydes, benzoic acids, anilines, amides, and aminopyridine have been successfully brominated in excellent regioselectivities and good yields under the typical reaction conditions. The features of KBr as brominating reagent, water as solvent, and mild conditions make this system an attractive synthetic procedure. [Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications for the following free supplemental resource(s): Full experimental and spectral details.]
- Hou, Jieping,Li, Zejiang,Jia, Xiao-Dong,Liu, Zhong-Quan
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supporting information
p. 181 - 187
(2013/12/04)
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- Base-promoted protodeboronation of 2,6-disubstituted arylboronic acids
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Facile based promoted deboronation of electron-deficient arylboronate esters was observed for arylboronates containing two ortho electron-withdrawing group (EWG) substituents. Among 30 representative boronates, only the diortho-substituted species underwe
- Lozada, Jerome,Liu, Zhibo,Perrin, David M.
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supporting information
p. 5365 - 5368
(2014/06/23)
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- Targeting the human parasite Leishmania donovani: Discovery of a new promising anti-infectious pharmacophore in 3-nitroimidazo[1,2-a]pyridine series
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We report herein the discovery of antileishmanial molecules based on the imidazo[1,2-a]pyridine ring. In vitro screenings of imidazopyridines belonging to our chemical library, toward the promastigotes stage of Leishmania donovani, J774A.1 murine and HepG2 human cells, permitted to identify three selective hit-compounds (12, 20 and 28). New derivatives were then synthesized to allow structure-activity and -toxicity relationships analyses, enabling to characterize a lead-compound (44) displaying both a high potency (IC 50 = 1.8 μM) and a good selectivity index, in comparison with three antileishmanial reference drug-compounds (amphotericin B, miltefosine and pentamidine). Moreover, lead-compound 44 also exhibits good in vitro activity against the intracellular amastigote stage of L. donovani. Thus, the 6-halo-3-nitro-2-(phenylsulfonylmethyl)imidazo[1,2-a]pyridine scaffold appears as a new promising selective antileishmanial pharmacophore, especially when substituted at position 8 by a bromine atom.
- Castera-Ducros, Caroline,Paloque, Lucie,Verhaeghe, Pierre,Casanova, Magali,Cantelli, Christophe,Hutter, Sébastien,Tanguy, Floriane,Laget, Michèle,Remusat, Vincent,Cohen, Anita,Crozet, Maxime D.,Rathelot, Pascal,Azas, Nadine,Vanelle, Patrice
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p. 7155 - 7164
(2013/11/06)
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- Integrated structure-based activity prediction model of benzothiadiazines on various genotypes of HCV NS5b polymerase (1a, 1b and 4) and its application in the discovery of new derivatives
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This work presents the first structure-based activity prediction model for benzothiadiazines against various genotypes of HCV NS5b polymerase (1a, 1b and 4).The model is a comprehensive workflow of structure-based field template followed by guided docking. The field template was used as a pre-filter and a tool to provide hits in good orientation and position. It was created based on detailed molecular interaction field analysis which includes Topomer CoMFA, grid independent analysis and Superstar. On the other hand, Guided docking was used as a refinement and assessment tool. It was actively directed by two scores: Moldock score as an interaction descriptor (r2 = 0.65) and a template similarity score as a measure for accurate binding-mode compliance. The docking template was based on energy-based pharmacophore analysis. The whole procedure was formulated and tweaked for both screening (ROC of AUC = 0.91) and activity prediction (r2 of 0.8) for the genotype 1a. In order to widen the model scope, linear interaction energy was used as a tool for predicting activities of other genotypes based on the docked ligand poses while mutation binding energy was used to investigate the effect of each amino acid mutation in genotype 4. The model was applied for structure-based fragment hopping by screening a library designed by reaction enumeration. A top scoring hit was used to generate a focused library such that it has lower TPSA than the original class ligands and thus better pharmacokinetic properties. After that, experimental validation was carried out by the synthesis of this library and its biological evaluation which yielded compounds that exhibit EC50 ranging from 1.86 to 23 μM.
- Ismail, Mohamed A.H.,Abou El Ella, Dalal A.,Abouzid, Khaled A.M.,Mahmoud, Amr H.
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experimental part
p. 2455 - 2478
(2012/05/05)
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- Oxidative bromination of imidazoheterocycle bromohydrates
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The behavior of imidazo[1,2-a]pyridinium, imidazo[1,2-a]pyrimidinium, and imidazo[2,1-b]thiazolium bromides derivatives in oxidative bromination reactions has been studied. It has been established that reaction products structures and their yields depend on the properties of the substituents in the bicycle and the oxidant concentration. 0009-3122/12/4710-12802012 Springer Science+Business Media, Inc.
- Kovalenko,Cherepakha,Kutrov,Shishkin,Shishkina
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experimental part
p. 1280 - 1285
(2012/07/27)
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- New bimetallic reactivity in Pt2II,III/Pt2 IV,IV transformation mediated by a benzene ring
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A new Pt2 II,II complex with the formula Pt 2(TPAB)Me4 (1), where TPAB = 1,2,4,5-tetrakis(5-(/p-C 7H15Ph)-7-azaindol- l-yl)benzene, has been synthesized. This molecule has excellent solubility in common solvents, which enabled our investigation of its reactions with a variety of oxidants to form Pt2 IV,IV species and the reverse reactions of the Pt2IV,IV species back to 1 via reduction. Despite the lack of direct Pt- ... -Pt interactions, the two Pt centers in 1 display distinct bimetallic cooperativity mediated by the central phenyl ring of the TPAB ligand. The most unusual finding is that the reactivity of 1 with MeOTf is highly dependent on the amount of molecular oxygen present in the reaction medium. In the absence Of O 2, the reaction of 1 with MeOTf produced [Pt2 IV,IV(TPAB)Me6][OTf]2 (6), while in the presence of O2, complex 7, Pt2IV,IV(TP AB)Me4(OTf)2, was obtained. Compound 1 was found to react readily with O2 at one atmosphere and ambient temperature to produce an insoluble and not yet fully characterized solid that further reacts with MeOTf to produce 7 quantitatively. NMR and single-crystal X-ray diffraction analyses established that the two PtIV centers in 6 are five-coordinate with a squarepyramidal geometry, while in 7 the two Pt IV centers are six-coordinate with an octahedral geometry. Most significantly, the central phenyl ring of the TPAB ligand was transformed to a cyclohexyldienyl in 7, while it remains unchanged in 6. Complex 1 also reacts readily with other oxidants such as CHCl3, PhICl2, Br 2 (CBr4), I2, and H2O2 to produce Pt2IV,IV(TPAB)Me4X2 (X = Cl, 2; Br, 3; I,4; OH, 5). The structures of 2-5 are similar to that of 7, showing the generality of the central phenyl ring mediated oxidation of the Pt2IV,IV system. Complexes 2 and 7 can be reduced and converted back to complex 1 via reactions with BH4-, as established by NMR experiments.
- Zhao, Shu-Bin,Cui, Qian,Wang, Suning
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scheme or table
p. 998 - 1003
(2010/04/25)
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- Efficient and regioselective bromination of aromatic compounds with ethylenebis(N-methylimidazolium) ditribromide (EBMIDTB)
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A regioselective and highly efficient method for bromination of phenol and aniline derivatives using ethylenebis(N-methylimidazolium) ditribromide (EBMIDTB) as an efficient reagent in dichloromethane at ambient temperature is reported. The reagent can be recovered and reused several times.
- Hosseinzadeh, Rahman,Tajbakhsh, Mahmood,Mohadjerani, Maryam,Lasemi, Zahra
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experimental part
p. 868 - 876
(2010/05/18)
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- PYRAZOLE COMPOUNDS
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The present invention is directed to compounds of Formula (I) and to pharmaceutically acceptable salts thereof, their synthesis, and their use as Raf inhibitors.
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Page/Page column 48
(2009/03/07)
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- Regioselective synthesis of substituted pyrrolopyridines based on Pd(II)-mediated cross coupling and base induced heteroannulation
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Novel pyrrolopyridines have been synthesized by an efficient, regioselective and catalytic method from commercially available and inexpensive 3-aminopyridine or 2-aminopyridine.
- Majumdar,Mondal
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p. 6951 - 6953
(2008/02/13)
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- An intriguing effect of lithium perchlorate dispersed on silica gel in the bromination of aromatic compounds by N-bromosuccinimide
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A convenient and efficient procedure for electrophilic aromatic bromination has been developed by mixing of N-bromosuccinimide and an aromatic compound at room temperature on the surface of silica gel mixed with solid anhydrous LiClO4. All of the substrates examined underwent clean electrophilic aromatic bromination in reaction times of a few minutes to afford the corresponding bromoarenes under neutral conditions in excellent yield. In the case of thiophenol, no substitution reaction occurred, and the corresponding disulfide was obtained in excellent yield.
- Bagheri, Mojtaba,Azizi, Najmedin,Saidi, Mohammad R.
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p. 146 - 149
(2007/10/03)
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- Synthesis and structure-activity relationships of pyrazine-pyridine biheteroaryls as novel, potent, and selective vascular endothelial growth factor receptor-2 inhibitors
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There is much evidence that direct inhibition of the kinase activity of vascular endothelial growth factor receptor-2 (VEGFR-2) will result in the reduction of angiogenesis and the suppression of tumor growth. Palladium-catalyzed C-C bond, C-N bond formation reactions were used to assemble various pyrazine-pyridine biheteroaryls as potent VEGFR-2 inhibitors. Among them, 4-{5-[6-(3-chloro-phenylamino)-pyrazin-2-yl]-pyridin-3-ylamino}-butan-1-ol (39) and N-{5-[6-(3-chloro-phenylamino)-pyrazin-2-yl]-pyridin-3-yl}-N′, N′-dimethyl-ethane-1,2-diamine (41) exhibited the highest kinase selectivity against fibroblast growth factor receptor kinase, platelet-derived growth factor receptor kinase, and glycogen synthase kinase-3. All of these compounds showed good cellular potency to inhibit VEGF-stimulated proliferation of human umbilical vein endothelial cells (HUVEC) but with modest effects on the unstimulated growth of HUVEC. The low inhibition of these compounds to the growth of tumor cell lines, such as HeLa, HCT-116, and A375 further confirms that these VEGFR-2 inhibitors are not cytotoxic agents. The in vivo antitumor activity of 39 and 41 were demonstrated in the A375 human melanoma xenograft nude mice model. Molecular modeling (QSAR analysis) was conducted in an attempt to rationalize the observed structure-activity relationship.
- Kuo, Gee-Hong,Prouty, Catherine,Wang, Aihua,Emanuel, Stuart,DeAngelis, Alan,Zhang, Yan,Song, Fengbin,Beall, Lawrence,Connolly, Peter J.,Karnachi, Prahba,Chen, Xin,Gruninger, Robert H.,Sechler, Jan,Fuentes-Pesquera, Angel,Middleton, Steven A.,Jolliffe, Linda,Murray, William V.
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p. 4892 - 4909
(2007/10/03)
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- Mild regioselective halogenation of activated pyridines with N-bromosuccinimide
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Regioselective mono and dihalogenations of amino, hydroxy and methoxy pyridines (2-, 3-, and 4-substituted) as well as 2,6-dimethoxy pyridine with N-bromosuccinimide in different solvents have been studied. Reactivity of the substrates decreases in the order amino>hydroxy>methoxy and regioselectivity depends on the position of the substituent (2-substituted > 3-substituted). In most of the cases we obtained monobrominated derivatives regioselectively and in high yields. Hydroxy and amino pyridines can also be dibrominated in almost quantitative yield with 2 equivalents of NBS.
- Canibano,Rodriguez,Santos,Sanz-Tejedor,Carreno,Gonzalez,Garcia-Ruano
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p. 2175 - 2179
(2007/10/03)
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- Synthesis of a fluorine-18 labeled derivative of epibatidine for in vivo nicotinic acetylcholine receptor PET imaging
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Epibatidine (exo-2-(2'-chloro-5'-pyridyl)-7-azabicyclo[2.2.1]heptane), a natural compound isolated from the skin of the Ecuadorian poison frog Epipedobates tricolor, is the most potent nicotinic acetylcholine receptor (nAChR) agonist reported to date. In order to visualize and quantify in vivo these receptors in human brain using Positron Emission Tomography (PET), [18F]norchlorofluoroepibatidine (exo-2-(2'-[18F]fluoro-5'-pyridyl)-7-azabicyclo[2.2.1]heptane), a fluorine-18 (t(1/2): 110min) radiolabeled derivative of epibatidine has been designed. The corresponding 2'-bromo-, 2'-iodo- and 2'-nitro exo-2-(5'-pyridyl)-7-azabicyclo[2.2.1]heptane analogues as labeling precursors, as well as norchlorofluoroepibatidine as a reference compound have been synthesized by reductive, stereoselective, palladium-catalyzed Heck-type coupling between an N-Boc protected azanorbornene and the corresponding halopyridine. [18F]Norchlorofluoroepibatidine has been radiolabeled with fluorine-18 by nucleophilic aromatic substitution from the corresponding Boc-protected halo- and nitro precursors using [18F]FK-K222 complex in DMSO by conventional heating (at 150-180°C for 10min) or microwave activations (at 100 Watt, for 1 to 2.5min), followed by TFA-removal of the protective group. Typically, using the microwave activation procedure, 60-80mCi (2.22-2.96 GBq) of pure [18F]norchlorofluoroepibatidine could be obtained in less than 2h (110-115min) from the bromo labeling precursor, with specific radioactivities of 1.5-2.5Ci/μmol (55.5-92.5GBq/μmol) calculated for End of Bombardment. The preliminary PET experiments in baboon (Papio papio) with [18F]norchlorofluoroepibatidine show a high uptake and a rapid accumulation of the radiotracer into the brain within 30min. In the thalamus, a nAChR rich area, uptake of radioactivity reached a maximum at 40min (10% I.D./100mL tissue). The ratio of radioactivity thalamus/cerebellum (the latter being a nAChR poor area) was 2 at 40min and increased with time, up to 4.3 at 160min. Its specific regiodistribution and its high ratio of specific-to-nonspecific binding confirm the ideal profile of [18F]norchlorofluoroepibatidine as a suitable radioligand for PET imaging of nAChRs in the brain. Copyright (C) 1999 Elsevier Science Ltd.
- Dolci, Lilian,Dolle, Frederic,Valette, Heric,Vaufrey, Francoise,Fuseau, Chantal,Bottlaender, Michel,Crouzel, Christian
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p. 467 - 479
(2007/10/03)
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- Halogenation of pyridinium-N-(2'-pyridyl)aminide: An easy synthesis of halo-2-aminopyridines
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The regioselective halogenation of pyridinium-N-(2'-pyridyl)aminide 1 with N-chloro, bromo or iodosuccinimide under mild conditions is described. The method, combined with a reduction of the N-N bond, allows an easy preparation of 5-halo and 3,5-dihalo-2-aminopyridines 4.
- Burgos,Delgado,Garcia-Navio,Izquierdo,Alvarez-Builla
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p. 8649 - 8654
(2007/10/02)
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- Pyridinium-N-(2-pyridyl)aminides: A selective approach to substituted 2-aminopyridines
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Differently substituted 2-aminopyridines have been prepared in two steps from pyridinium-N-(2-pyridyl)aminide.
- Carceller, Rosa,Garcia-Navio, Jose L.,Izquierdo, Maria L.,Alvarez-Builla, Julio
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p. 2019 - 2020
(2007/10/02)
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- SYNTHESES WITH AROMATIC NITRAMINES, VI SUBSTITUENT EFFECT IN THE PHOTOLYTIC REARRANGEMENT OF NITRAMINOPYRIDINES
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All isomeric ring-substituted methyl-2-nitraminopyridines, both 3-nitro- and 5-nitro-2-nitraminopyridines, 5-chloro- and 3-carboxy-2-nitraminopyridines, as well as 3,5-dibromo-2-nitraminopyridine were photolyzed in methanol by irradiation with a low-pressure mercury lamp (253.7 nm).Preference was generally noted for the migration of the side-chain nitro group to the vicinal β-position. 3,5-Dibromo-2-nitraminopyridine gave both 2-amino-3,5-dibromopyridine and 3,5-dibromopyridine-2-one.The ratio of the preparative and quantum yields of the two products were 2.5 and 3.0, respectively.
- Sepiol, Jadwiga,Tomasik, Piotr
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p. 333 - 338
(2007/10/02)
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- REGIOSELECTIVE MONOBROMINATION OF AROMATIC AMINES WITH TETRABUTYLAMMONIUM TRIBROMIDE
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A simple and efficient method for monobromination of aromatic amines predominantly in the para position is reported.Tetrabutylammonium tribromide is used at 20 deg C and yields of parabromoanilines are higher than 90percent.
- Berthelot, J.,Guette, C.,Essayegh, M.,Desbene, P.L.,Basselier, J.J.
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p. 1641 - 1646
(2007/10/02)
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- Bromination of Some Pyridine and Diazine N-Oxides
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Selected monosubstituted pyridines, pyrazines, pyrimidines, and their N-oxides, having an electron-donating substituent, were successfully brominated under very mild conditions.The N-oxide function itself is not sufficient to cause these ?-deficient systems to undergo electrophilic aromatic halogenation.Only strongly electron-donating substituents (amino groups) activate the heterocyclic nucleus toward bromination.These substituents direct the electrophilic substitution ortho/para to them with or without the N-oxide group present.Pyridine and diazines with moderately activating substituents such as alkoxy groups are brominated only when their ortho/para activation is augmented by the activation of the N-oxide funtion.Failure to brominate 5-methoxypyrimidine 1-oxide may well reflect the greater ? deficiency of the pyrimidine ring.
- Paudler, William W.,Jovanovic, Misa V.
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p. 1064 - 1069
(2007/10/02)
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- CYCLOHEXYLATION OF N-ETHYL-2-PYRIDONE IN THE PRESENCE OF ALUMINIUM CHLORIDE
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The possibility of direct alkylation of N-ethyl-2-pyridone under Friedel-Crafts conditions was demonstrated.The reaction of N-ethyl-2-pyridone with cyclohexyl chloride in the presence of aluminium chloride took place at positions 3 and 5.
- Saidova, F. M.,Binchkauskas, V. Sh.,Khorev, S. G.,Enikeev, E. Ya.
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p. 353 - 357
(2007/10/02)
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