- Use of highly reactive, versatile and air-stable palladium-phosphinous acid complex [(t-Bu)2P(OH)]2PdCl2 (POPd) as a catalyst for the optimized Suzuki-Miyaura cross-coupling of less reactive heteroaryl chlorides and arylboronic acids
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Using highly reactive air-stable palladium-phosphinous acid complex [(t-Bu)2P(OH)]2PdCl2 (POPd) as a catalyst, synthesis of heteroaryl-aryl cross-coupled products via palladium-catalyzed Suzuki-Miyaura coupling of less reactive substituted 3-chloropyridines with arylboronic acids was achieved in high yields.
- Khanapure, Subhash P.,Garvey, David S.
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- Selective Synthesis of Substituted Pyridines and Pyrimidines through Cascade Annulation of Isopropene Derivatives
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Diverse substituted pyridines and pyrimidines with high selectivity were obtained using a concise and efficient protocol developed herein. The reaction proceeds via metal-free cascade annulation of isopropene derivatives. Using isopropene derivatives as C3 synthons, NH4I as the “N” source, and formaldehyde or dimethyl sulfoxide as the carbon source, this reaction realizes the efficient formation of intermolecular C-N and C-C bonds.
- Chen, Lu,He, Runfa,Huang, Yubing,Li, Jiaming,Li, Jian,Li, Yibiao,Liu, Jiasheng,Liu, Yang
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supporting information
p. 1620 - 1625
(2022/03/14)
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- Pd Reaction Intermediates in Suzuki-Miyaura Cross-Coupling Characterized by Mass Spectrometry
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Palladium-catalyzed Suzuki-Miyaura (SM) coupling is widely utilized in the construction of carbon-carbon bonds. In this study, nanoelectrospray ionization mass spectrometry (nanoESI-MS) is applied to simultaneously monitor precatalysts, catalytic intermediates, reagents, and products of the SM cross-coupling reaction of 3-Br-5-Ph-pyridine and phenylboronic acid. A set of Pd cluster ions related to the monoligated Pd (0) active catalyst is detected, and its deconvoluted isotopic distribution reveals contributions from two neutral molecules. One is assigned to the generally accepted Pd(0) active catalyst, seen in MS as the protonated molecule, while the other is tentatively assigned to an oxidized catalyst which was found to increase as the reaction proceeds. Oxidative stress testing of a synthetic model catalyst 1,5-cyclooctadiene Pd XPhos (COD?Pd-XPhos) performed using FeCl3 supported this assignment. The formation and conversion of the oxidative addition intermediate during the catalytic cycle was monitored to provide information on the progress of the transmetalation step.
- Chen, Xingshuo,Wei, Zhenwei,Huang, Kai-Hung,Uehling, Mycah,Wleklinski, Michael,Krska, Shane,Makarov, Alexey A.,Nowak, Timothy,Cooks, R. Graham
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- Base-promoted one-pot synthesis of pyridine derivatives via aromatic alkyne annulation using benzamides as nitrogen source
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In the presence of Cs2CO3, the first simple, efficient, and one-pot procedure for the synthesis of 3,5-diaryl pyridines via a variety of aromatic terminal alkynes with benzamides as the nitrogen source in sulfolane is described. The formation of pyridine derivatives accompanies the outcome of 1,3-diaryl propenes, which are also useful intermediates in organic synthesis. Thus, pyridine ring results from a formal [2+2+1+1] cyclocondensation of three alkynes with benzamides, and one of the alkynes provides one carbon, whilst benzamides provide a nitrogen source only. A new transformation of alkynes as well as new utility of benzamide are found in this work.
- Ashiq, Muhammad Naeem,Hua, Ruimao,Iqbal, Muhammad Asif,Mehmood, Hina
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supporting information
(2021/11/08)
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- Two C=C Bond Participation in Annulation to Pyridines Based on DMF as the Nonadjacent N and C Atom Donors
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Two C=C bond participation in annulation to pyridines using N,N-dimethylformamide (DMF) as the N1 and C4 synthons has been carried out. In this reaction, DMF contributed one N atom and one C atom to two disconnected positions of pyridine ring, with no need for an additional nitrogen source. Two C=C bonds in two molecules of substituted styrenes offered four carbon atoms in the presence of iodine and persulfate. With the optimized conditions in hand, both symmetric and unsymmetric diaryl-substituted pyridines were obtained in useful yields. On the basis of relevant literature and a series of control experimental results, a possible mechanism was proposed in this work, which may demonstrate how DMF provides both N1 and C4 sources.
- Su, Miao-Dong,Liu, Hai-Ping,Cao, Zhong-Zhong,Liu, Yufeng,Li, Hui,Nie, Zhi-Wen,Yang, Tong-Lin,Luo, Wei-Ping,Liu, Qiang,Guo, Can-Cheng
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p. 13446 - 13453
(2021/10/12)
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- Method for constructing 3,5-disubstituted pyridine from aryl ethylene and N,N-dimethylformamide through cyclization reaction
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The invention discloses a method for constructing 3,5-disubstituted pyridine from aryl ethylene and N,N-dimethylformamide through a cyclization reaction. The method comprises carrying out cyclizationon the aryl ethylene, the N,N-dimethylformamide and peroxydisulfate under the catalytic action of iodized salt to obtain the 3,5-disubstituted pyridine. According to the method, iodine salt is utilized to catalyze one-step oxidative cyclization of the aryl ethylene and DMF to synthesize 3,5-disubstituted pyridine, and the method has the advantages of low cost of raw materials and catalysts, mild reaction conditions, capability of obtaining symmetric 3,5-disubstituted pyridine with high selectivity and high yield and the like.
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Paragraph 0084; 0085; 0086; 0087; 0088
(2020/09/09)
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- Method for constructing 3,5-disubstituted pyridine by utilizing mixed styrene derivative and N,N-dimethylformamide
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The invention discloses a method for constructing 3,5-disubstituted pyridine by utilizing mixed styrene derivative and N,N-dimethylformamide. The method comprises the following step: subjecting the mixed styrene derivative, N,N-dimethylformamide and peroxydisulfate to a cyclization reaction under the catalytic action of iodized salt so as to obtain symmetrical and asymmetrical mixed 3,5-disubstituted pyridine products at the same time. According to the method, 3,5-disubstituted pyridine is synthesized from the mixed styrene derivative and DMF through one-step oxidative cyclization under the catalysis of iodate; and the method has the advantages of low raw material and catalyst cost, mild reaction conditions, capability of realizing high-yield preparation of the symmetrical and asymmetrical3,5-disubstituted pyridine products at the same time and the like.
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Paragraph 0101-0107
(2020/08/27)
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- Pd-Catalyzed Decarboxylation and Dual C(sp3)-H Functionalization Protocols for the Synthesis of 2,4-Diarylpyridines
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The Pd-catalyzed decarboxylation and dual C(sp3)-H bond functionalization approaches have been described for the preparation of symmetrical and unsymmetrical 2,4-diarylpyridines. The developed transformations were realized using nonactivated aromatic ketones and amino acids as C-N sources. The efficacy of the catalyst and reagent combination drives the transformation toward the formation of desired products with high yields and selectivity. The described reaction conditions have seduced the self-reaction of phenylalanine via [2 + 2 + 2] cycloaddition and minimized the formation of 3,5-phenylpyridine as a side product, whereas using glycine as a C-N source, the corresponding 2,6-diarylpyridines were formed as minor products.
- Gujjarappa, Raghuram,Vodnala, Nagaraju,Kumar, Mohan,Malakar, Chandi C.
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p. 5005 - 5020
(2019/04/25)
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- Olefin Cyclopropanation by Radical Carbene Transfer Reactions Promoted by Cobalt(II)/Porphyrinates: Active-Metal-Template Synthesis of [2]Rotaxanes
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A CoII/porphyrinate-based macrocycle in the presence of a 3,5-diphenylpyridine axial ligand functions as an endotopic ligand to direct the assembly of [2]rotaxanes from diazo and styrene half-threads, by radical-carbene-transfer reactions, in excellent 95 % yield. The method reported herein applies the active-metal-template strategy to include radical-type activation of ligands by the metal-template ion during the organometallic process which ultimately yields the mechanical bond. A careful quantitative analysis of the product distribution afforded from the rotaxane self-assembly reaction shows that the CoII/porphyrinate subunit is still active after formation of the mechanical bond and, upon coordination of an additional diazo half-thread derivative, promotes a novel intercomponent C?H insertion reaction to yield a new rotaxane-like species. This unexpected intercomponent C?H insertion illustrates the distinct reactivity brought to the CoII/porphyrinate catalyst by the mechanical bond.
- Alcantara, Arthur F. P.,Fontana, Liniquer A.,Rigolin, Vitor H.,Andrade, Yuri F. S.,Ribeiro, Marcos A.,Barros, Wdeson P.,Ornelas, Catia,Megiatto, Jackson D.
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supporting information
p. 8979 - 8983
(2018/07/24)
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- Photoredox C-F Quaternary Annulation Catalyzed by a Strongly Reducing Iridium Species
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We report a fac-Ir(ppy)3?-IrII-IrIII photocatalytic cycle involving t-BuOK as the terminal reductant in a visible-light-induced sp2 C-F quaternary annulation reaction that proceeds in yields up to 98%. Because of the high activity of the IrII(ppy)3 catalyst, even at a loading of 50 ppm, the annulation reaction was able to compete with an uncatalyzed nucleophilic aromatic substitution reaction. The annulation reaction was stereoconvergent, and an annulated product was synthesized with complete retention of enantiomeric excess.
- Dai, Peng,Ma, Junyu,Huang, Wenhao,Chen, Wenxin,Wu, Na,Wu, Shengfu,Li, Ying,Cheng, Xu,Tan, Renxiang
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p. 802 - 806
(2018/02/14)
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- Oxidative Trimerization of Amino Acids: Selective Synthesis of 2,3,5-Trisubstituted Pyridines
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An oxidative trimerization of three amino acids has been realized to furnish 2,3,5-trisubstuitued pyridines in both cross- and homo-trimerization types. This method is capable of converting simple linear biomass material to heterocycles, which features in
- Xiang, Jia-Chen,Cheng, Yan,Wang, Zi-Xuan,Ma, Jin-Tian,Wang, Miao,Tang, Bo-Cheng,Wu, Yan-Dong,Wu, An-Xin
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supporting information
p. 2997 - 3000
(2017/06/07)
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- Synthesis of Trisubstituted Pyridines via Chemoselective Suzuki–Miyaura Coupling of 3,5- and 4,6-Dibromo-2-tosyloxypyridines
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Chemoselective Suzuki–Miyaura reactions on 3,5- and 4,6-dibromo-2-tosyloxypyridines have been studied for the preparation of trisubstituted pyridines. The optimized conditions allow for a facile access to 3,5- and 4,6-diaryl-2-tosyloxypyridines in yields of 8 to 99%. Further functionalization such as palladium-catalyzed amination and copper-free Sonogashira reaction of the tosylate group in the diarylpyridine derivatives obtained was accomplished for the synthesis of novel and biologically relevant trisubstituted pyridines. The formal synthesis of ficuseptine, a bioactive alkaloid, has also been achieved via the palladium-catalyzed cross-coupling reaction of 3,5-dibromo-2-tosyloxypyridine in 5 steps from 3,5-dibromo-2-hydroxypyridine with 50% overall yield. (Figure presented.).
- Park, Cho-Hee,Kwon, Yong-Ju,Oh, In-Young,Kim, Won-Suk
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supporting information
p. 107 - 119
(2017/01/14)
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- Insight into Copper Catalysis: In Situ Formed Nano Cu2O in Suzuki-Miyaura Cross-Coupling of Aryl/Indolyl Boronates
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A ligand-free copper catalyzed Suzuki-Miyaura coupling of 3,5-diiodopyridine with aryl and indole boronates has been explored in good to excellent yields. In situ generation of nano-Cu2O from CuCl2 under the reaction conditions has been discovered for the first time. The generality of the reaction was further demonstrated by the arylation of 5-iodopyrimidine, iodopyridines, iodobenzenes, and diiodobenzenes and resulted in good to moderate yields. Moreover, bisindole alkaloid Scalaridine A has been successfully synthesized in 60% overall yield.
- Ranjani, Ganapathy,Nagarajan, Rajagopal
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supporting information
p. 3974 - 3977
(2017/08/14)
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- Pd-Catalyzed Ligand-Free Synthesis of Arylated Heteroaromatics by Coupling of N-Heteroaromatic Bromides with Iodobenzene Diacetate, Iodosobenzene, or Diphenyliodonium Salts
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An efficient method for synthesizing arylated heteroaromatics has been reported via Pd-catalyzed ligand-free cross-coupling of N-heteroaromatic bromides with iodine(III) reagents under mild conditions. Iodobenzene diacetate, iodosobenzene, and diphenyliod
- Wang, Xiajun,He, Yongqin,Ren, Mengdan,Liu, Shengkang,Liu, He,Huang, Guosheng
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p. 7958 - 7962
(2016/09/09)
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- Molecular Iodine-Mediated Chemoselective Synthesis of Multisubstituted Pyridines through Catabolism and Reconstruction Behavior of Natural Amino Acids
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A new process has been developed for the selective construction of 2,6-disubstituted, 2,4,6-trisubstituted, and 3,5-disubstituted pyridines based on the catabolism and reconstruction behaviors of amino acids. Molecular iodine was used as a tandem catalyst to trigger the decarboxylation-deamination of amino acids and to promote the subsequent formation of the pyridine products.
- Xiang, Jia-Chen,Wang, Miao,Cheng, Yan,Wu, An-Xin
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supporting information
p. 24 - 27
(2016/01/15)
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- Iron-Mediated One-Pot Synthesis of 3,5-Diarylpyridines from β-Nitrostyrenes
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An operationally simple and mild one-pot protocol for the synthesis of a variety of 3,5-diarylpyridines from β-nitrostyrenes was achieved by using elemental iron. This reaction proceeds via reduction of the nitro group, resulting in in situ imine formation followed by trimolecular condensation with concomitant debenzylative aromatization. By employing this method, a series of symmetrical and unsymmetrical 3,5-diarylpyridines were synthesized with good to excellent yields. In addition, this method was also utilized for the synthesis of Sch-21418, an anti-inflammatory agent on gram scale.
- Sathish, Manda,Chetna, Jadala,Hari Krishna, Namballa,Shankaraiah, Nagula,Alarifi, Abdullah,Kamal, Ahmed
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p. 2159 - 2165
(2016/03/15)
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- Cu-Catalyzed concise synthesis of pyridines and 2-(1 H)-pyridones from acetaldehydes and simple nitrogen donors
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A highly selective copper-catalyzed concise synthesis of 3,5-diarylpyridine and 2-(1H)-pyridone has been achieved through cascade Chichibabin-type cyclization, C(sp3)-C(sp3) cleavage, and aerobic oxidation. Azide, ceric ammonium nitrate (CAN), and 2-aminopyridine are disclosed as efficient nitrogen donors in this Cu-catalysis using O2 as the oxidant. Water and molecular oxygen were employed as the oxygen source in the case of oxygenation.
- Li, Ziyuan,Huang, Xiaoqiang,Chen, Feng,Zhang, Chun,Wang, Xiaoyang,Jiao, Ning
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supporting information
p. 584 - 587
(2015/03/04)
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- Palladacycle-catalyzed Suzuki-Miyaura reaction of aryl/heteroaryl halides with MIDA boronates in EtOH/H2O or H2O
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With good to excellent yields, a series of mono- or diheteroaryl compounds were synthesized via the palladacycle-catalyzed Suzuki-Miyaura reaction of various N-methyliminodiacetic acid (MIDA) boronates with aryl/heteroaryl halides in EtOH/H2O or H2O. This journal is the Partner Organisations 2014.
- Li, Yabo,Wang, Jingran,Wang, Zhiwei,Huang, Mengmeng,Yan, Beiqi,Cui, Xiuling,Wu, Yusheng,Wu, Yangjie
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p. 36262 - 36266
(2014/11/08)
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- Metal-free synthesis of substituted pyridines from aldehydes and NH4OAc under air
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A metal-free and efficient method for the synthesis of substituted pyridines with aldehydes and NH4OAc under mild conditions using air as the oxidant was developed. This oxidative cyclization process involves direct C-H bond functionalization, C-C/C-N bond formation and C-C bond cleavage.
- Yan, Rulong,Zhou, Xiaoqiang,Li, Ming,Li, Xiaoni,Kang, Xing,Liu, Xingxing,Huo, Xing,Huang, Guosheng
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p. 50369 - 50372
(2014/12/10)
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- Palladium nanoparticles catalyzed Suzuki cross-coupling reactions in ambient conditions
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An efficient pathway to synthesize biaryls and terphenyls through ligand-free palladium nanoparticles (PdNPs) catalyzed Suzuki cross-coupling reactions has been developed. Mild reaction conditions, high yields of desired products, absence of inert atmosphere and short reaction times are the notable features of this method.
- Mandali, Pavan Kumar,Chand, Dillip Kumar
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- Scope of the palladium-catalyzed aryl borylation utilizing bis-boronic acid
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The Suzuki-Miyaura reaction has become one of the more useful tools for synthetic organic chemists. Until recently, there did not exist a direct way to make the most important component in the coupling reaction, namely the boronic acid. Current methods to make boronic acids often employ harsh or wasteful reagents to prepare boronic acid derivatives and require additional steps to afford the desired boronic acid. The scope of the previously reported palladium-catalyzed, direct boronic acid synthesis is unveiled, which includes a wide array of synthetically useful aryl electrophiles. It makes use of the newly available second generation Buchwald XPhos preformed palladium catalyst and bis-boronic acid. For ease of isolation and to preserve the often sensitive C-B bond, all boronic acids were readily converted to their more stable trifluoroborate counterparts.
- Molander, Gary A.,Trice, Sarah L. J.,Kennedy, Steven M.,Dreher, Spencer D.,Tudge, Matthew T.
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supporting information; experimental part
p. 11667 - 11673
(2012/09/05)
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- The catalytic activity of a novel recyclable alkoxypalladium complex in Suzuki reaction
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A novel palladium complex based on N,O-ligand was synthesized, which shows a high catalytic activity in the Suzuki cross-coupling reaction without using any phosphine ligand. More importantly, no significant loss of the catalytic activity was observed after six recycles. We suggest that this catalyst has commercial and industrial potential in the future. Graphical abstract:
- Li, Yabo,Mi, Xia,Huang, Mengmeng,Cai, Ranran,Wu, Yangjie
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experimental part
p. 8502 - 8508
(2012/10/08)
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- A metal-free decarboxylative cyclization from natural α-amino acids to construct pyridine derivatives
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A metal-free decarboxylative cyclization from natural α-amino acids was developed and applied in the preparation of pyridine derivatives. By virtue of this method, a series of pyridines containing the moiety of natural α-amino acids can be synthesized efficiently from the corresponding natural α-amino acids. The Royal Society of Chemistry.
- Wang, Qiang,Wan, Changfeng,Gu, Yang,Zhang, Jintang,Gao, Lingfeng,Wang, Zhiyong
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supporting information; experimental part
p. 578 - 581
(2011/05/06)
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- Use of the curtius rearrangement of acryloyl azides in the synthesis of 3,5-disubstituted pyridines: Mechanistic studies
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A series of disubstituted pyridine derivatives was synthesized from the corresponding acryloyl azides by acetic acid-promoted cycloaddition. This represents a novel and convenient synthetic approach to the symmetric 3,5-disubstituted pyridines. The nature of the substituent on the double bond and the utilized solvent were found to be crucial to the yield of pyridines. The reactivity of the acid-promoted cycloaddition increases with the presence of aryl groups, such as phenyl and pyridinyl. We also explored the comprehensive mechanism by the acid-promoted cycloaddition of 13C-labeled cinnamoyl azide. The symmetric 3,5-disubstituted pyridines were synthesized from acryloyl azides by acetic acid-promoted trimolecular condensation.
- Chuang, Ta-Hsien,Chen, Yu-Chi,Pola, Someshwar
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experimental part
p. 6625 - 6630
(2010/11/18)
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- Palladium nanoparticles supported on polyaniline nanofibers as a semi-heterogeneous catalyst in water
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(Chemical Equation Presented) A tandem catalyst for Suzuki coupling of activated or deactivated aryl chlorides and aryl boronic acids in water and for phenol synthesis from aryl chlorides in 1:1 water/dioxane was obtained by supporting palladium nanoparticles on polyaniline nanofibers (PANI; see TEM image). Thus, 2-phenylphenol was synthesized from 1,2-dichlorobenzene (see equation).
- Gallon, Benjamin J.,Kojima, Robert W.,Kaner, Richard B.,Diaconescu, Paula L.
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p. 7251 - 7254
(2008/09/17)
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- β-Oxo amides: Inexpensive and efficient ligands for the palladium-catalyzed Suzuki-Miyaura cross-coupling reaction
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β-Oxo amides were found to be inexpensive and efficient ligands for the palladium-catalyzed Suzuki-Miyaura cross-coupling reaction. In the presence of palladium(II) acetate and N-(4-methoxyphenyl)-3-oxobutanamide (L7), a variety of aryl halides, including deactivated aryl chlorides and heteroaryl halides, were successfully coupled to arylboronic acids in moderate to excellent yields providing very high turnover numbers (maximum TON 950,000 and TOF 79,167). It is noteworthy that the reaction is conducted under mild and aerobic conditions. Georg Thieme Verlag Stuttgart.
- Li, Jin-Heng,Zhang, Yue-Hua,Song, Ren-Jie,Xie, Ye-Xiang,Deng, Chen-Liang,Liang, Yun
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p. 2957 - 2966
(2008/03/13)
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- Remarkable Chichibabin-type cyclotrimerisation of 3-nitrotyrosine, tyrosine and phenylalanine to 3,5-diphenylpyridine derivatives induced by hypochlorous acid
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Reaction of 3-nitrotyrosine with HOCl in aqueous phosphate buffer (pH 7.4) leads to a mixture of extractable products, including 3,5-di(4-hydroxy-3- nitrophenyl)pyridine (15% isolated yield) and 3,5-di(4-hydroxy-3-nitrophenyl)-2- (4-hydroxy-3-nitrophenylmethyl)pyridine (3%) arising by a Chichibabin-like pyridine synthesis via N-chloroimine intermediates. Under the same conditions, phenylalanine gives 3,5-diphenylpyridine in 9% isolated yield, while tyrosine leads to 3,5-di(4-hydroxyphenyl)pyridine (3%) and 3-(3-chloro-4-hydroxyphenyl)- 5-(4-hydroxyphenyl)pyridine (3%).
- Panzella,Di Donato,Comes,Napolitano,Palumbo,D'Ischia
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p. 6457 - 6460
(2007/10/03)
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- Synthesis and catalytic activity of a poly(N,N-dialkylcarbodiimide)/ palladium nanoparticle composite: A case in the Suzuki coupling reaction using microwave and conventional heating
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Poly(N,N-dialkylcarbodiimide) was found to be an effective polymeric ligand system for preparing and stabilizing palladium nanoparticles (1-5 nm). The composite material prepared in situ was found to be a robust catalyst for the Suzuki coupling reaction under microwave or regular heating.
- Liu, Yubiao,Khemtong, Chalermchai,Hu, Jun
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p. 398 - 399
(2007/10/03)
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- Cross Mannich Reaction of Aldehydes; Efficient Synthesis of Substituted Pyridines
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Symmetrically and unsymmetrically substituted pyridines were obtained in highly efficient one-pot procedures starting from α-unbranched aldehydes and iminium salts.
- Winter, Andreas,Risch, Nikolaus
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p. 2667 - 2670
(2007/10/03)
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- Palladium-catalyzed carbonylative coupling of pyridine halides with aryl boronic acids
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The carbonylative Suzuki cross-coupling of a variety of mono-iodopyridines and bromopyridines (1a,b, 3a-c, 5) catalyzed by palladium-phosphane systems has been studied to prepare benzoylpyridine derivatives (2, 4, 6). The selectivity and the rate of the reaction are highly dependent on the reaction conditions, i.e. nature of the palladium catalyst precursor, solvent, temperature and CO pressure. The main side-products arise from direct, non-carbonylative cross-coupling. Under optimized conditions, benzoylpyridines are recovered in high yields (80-95%). The order of reactivity decreases from iodo- to bromopyridines and from 2-, 4- to 3-substituted halopyridines. The reactivity of dihalopyridines has been investigated; 2,6-dibromopyridine (7) and 3,5-dibromopyridine (11) are selectively transformed into either the corresponding benzoyl-phenylpyridine (8, 12) or the corresponding dibenzoylpyridine (9, 13). Dissymmetric 2,5-dihalopyridines (15a,b) are transformed into 2-benzoyl-5-bromopyridine (16) or 2,5-dibenzoylpyridine (17) in high yields.
- Couve-Bonnaire, Samuel,Carpentier, Jean-Fran?ois,Mortreux, André,Castanet, Yves
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p. 2793 - 2799
(2007/10/03)
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- Pyrolysis/GC/MS Analysis of N-(1-Deoxy-D-fructos-1-yl)-L-phenylalanine: Identification of Novel Pyridine and Naphthalene Derivatives
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Pyrolysis/GC/MS has been employed to analyze phenylalanine specific products formed during Maillard reaction. Phenylalanine Amadori product and different model systems containing phenylalanine and glucose, ribose, or glycerladehyde were studied. Ribbon py
- Keyhani, Anahita,Yaylayan, Varoujan A.
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p. 223 - 229
(2007/10/03)
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- Process for the preparation of substituted pyridines via 1-aza-1,3-butadienes and the 1-aza-1,3-butadiene intermediates
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Process for the preparation of substituted pyridines by allowing 1-aza-1,3-butadienes to react, in the presence of a catalytic amount of secondary amine and acid, with an aldehyde or ketone, and new 1-aza-1,3-butadienes which are used in this process. Said pyridines can be obtained in high yield in a simple process with a short reaction time. The 1-aza-1,3-butadiene can, if so desired, be prepared in situ from an imine and an aldehyde.
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- Selectivities in the formation of pyridines and pyrimidines by ammonia-induced cyclocondensations of vinamidiniums
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Arylvinamidines (2-, 3- or 4-aryl-4-(N,N-dimethyl)amino-1-azabuta-1,3-dienes), generated from 1,1,5,5-tetramethyl-2- or 3-phenyl-1,5-diazapentadienium salts, cyclocondense orientation-specifically under two regioselections forming 1-4'+4-3' and 1-2'+4-1' bonds on exposure to ammonia. The initial cyclates aromatise eliminatively to give mixtures of diarylpyridines and arylpyrimidines. The 2-arylvinamidines do not participate as 2-centre reactants and their 4-aryl isomers not as 4-centre reactants in the cyclocondensations which appear to be stepwise and not concerned. Reasons for the selective participation appear to be that the required eliminations from the initial cyclates are disfavoured in the first case and that a geometric factor prevents cyclate-formation in the second.
- Natarajan Balasubrahmanyam,Jeyashri, Bommuswamy,Narayanan Namboothiri, Irishi N.
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p. 8127 - 8142
(2007/10/02)
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- Synthesis of alkyl- and aryl-substituted pyridines from (α,β-unsaturated) imines or oximes and carbonyl compounds
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Reaction of a variety of (α,β-unsaturated) imines or oximes with aliphatic aldehydes or cyclic ketones in the presence of a secondary amine afforded alkyl-, and/or aryl-, and/or cycloalkyl-substituted pyridines. To explain their formation, a hetero Diels-Alder reaction has been postulated, in which an 1-aza-1,3-butadiene reacts with an in situ generated enamine.
- Vijn,Arts,Green,Castelijns
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p. 573 - 578
(2007/10/02)
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- Bridged Hydroquinolines
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The pyridannulation procedure of condensing vinamidinium salts with ketones having a free α-methylene has been adapted to prepare 3-substituted 5,6,7,8-tetrahydroquinolines; characterization data for the seven systems synthesized are reported.Conditions required are less drastic than those for recently reported alternative approaches to analogous systems.The adaption has considerable generality even though 5,8-methano-bridged 5,6,7,8-tetrahydroquinolines are not accessible through it.Chirality in the starting ketone, not affected by exposure to enolizing conditions, is preserved in the pyridannulated products.
- Balasubrahmanyam, S. N.,Jeyashri, B.
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p. 559 - 562
(2007/10/02)
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- Ammonia-induced Cyclization of Vinamidinium Systems
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In the course of adapting known reactions of vinamidinium (aminoiminopropenium) systems for preparing certain 2,3-cycloalkenopyridines bearing aryl substituents in the hetero ring, the concomitant formation of 3,5-diarylpyridines (A) is noticed.It has been confirmed that products A arise from a direct reaction of ammonia with 3-aryl-1,1,5,5-tetramethyl-1,5-diazapentadienium salts (B), the vinamidiniums taken.In the mechanism envisaged this direct reaction is thought to be initiated by the displacement of a dimethylamino group in B by ammonia.The formed species undergo branched dimerization, eventually yielding dienes for which both concerted and stepwise pathways are available for forming C5-N cyclates which can aromatize to yield A.Features of this mechanism, postulated for species B which are C-2 substituted propeniums, are compared with those of mechanisms considered as operative in cases of C-1 substituted ethenyl systems known to yield pyridines of structures similar to A on reaction with ammonia.The vantage provided by the apparent generality of these features has enabled an explanation for variation of product composition from exclusively a 3-acetylpyridine to exclusively 2-acetylaniline through a mixture thereof when the nitrogen atom of the monoenamine of acetylacetone is progressively alkylated and made to undergo cyclizing reactions.
- Jeyashri, B.,Balasubrahmanyam, S. N.
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p. 341 - 349
(2007/10/02)
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- Novel Synthesis of 3,5-Disubstituted Pyridines by 1,4-Cycloaddition of 1-Aza-1,3-butadienes with Enamines
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A new method for the synthesis of 3,5-disubstituted pyridines is described.Reactions of the N-substituted methanimines 1 with the β-substituted enamines 2 give 1-aza-1,3-butadienes 3a-3i and/or symmetrically 3,5-disubstituted pyridines 4a-c,e-h in moderate to good yields.At reaction temperatures of 150 deg C the azadienes 3 are the predominant products, and the reaction provides a good route to 1-azadienes with no substituent at the 4-position.At reaction temperatures of 200 deg C, and particularly using N-tert-butylmethanimine 1a and p-toluenesulfonic acid catalyst, the principal products are symmetrically 3,5-disubstituted pyridines.The cycloaddition was shown to proceed via the azabutadiene intermediate 3.Reactions of 3 with the enamines 2 lead to unsymmetrically 3,5-disubstituted pyridines.The mechanisms of these cycloadditions are discussed.
- Komatsu, Mitsuo,Takamatsu, Shigeki,Uesaka, Masatoshi,Yamamoto, Shinji,Ohshiro, Yoshiki,Agawa, Toshio
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p. 2691 - 2699
(2007/10/02)
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- SYNTHESIS OF ALKYL-SUBSTITUTED ARYLPYRIDINES IN THE VAPOR PHASE BY THE CHICHIBABIN METHOD
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An industrial cadmium calcium phosphate catalyst was used in the syntheses of pyridine bases in the vapor phase by the Chichibabin method (condensation of carbonyl compounds with ammonia).Alkyl-substituted arylpyridines with the aryl radical at C2, C3, or C4 are formed during the condensation of aromatic aldehydes and ammonia with saturated and unsaturated aldehydes and also with methyl alkyl ketones.
- Soldatenkov, A. T.,Fedorov, V. O.,Chandra, R.,Polosin, V. M.,Mikaya, A. I.,Prostakov, N. S.
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p. 179 - 185
(2007/10/02)
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