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https://www.readbyqxmd.com/read/29345946/cooperative-metal-ligand-catalyzed-intramolecular-hydroamination-and-hydroalkoxylation-of-allenes-using-a-stable-iron-catalyst
#1
Osama El-Sepelgy, Aleksandra Brzozowska, Jan Sklyaruk, Yoon Kyung Jang, Viktoriia Zubar, Magnus Rueping
A new iron-catalyzed chemoselective intramolecular hydroamination and hydroalkoxylation of the readily available α-allenic amines and alcohols to valuable unsaturated 5-membered heterocycles, 2,3-dihydropyrrole and 2,3-dihydrofuran, is reported. Effective selectivity control is achieved by a metal-ligand cooperative activation of the substrates. The mild reaction conditions and the use of low amounts of an air and moisture stable iron catalyst allow for the hydrofunctionalization of a wide range of allenes bearing different functional groups in good yields in the absence of base or any sensitive additives...
January 18, 2018: Organic Letters
https://www.readbyqxmd.com/read/29345128/synthesis-of-%C3%AE-formylated-n-heterocycles-and-their-1-1-diacetates-from-inactivated-cyclic-amines-involving-an-oxidative-ring-contraction
#2
Fang Wang, Yan He, Miaomiao Tian, Xinying Zhang, Xuesen Fan
A novel synthesis of pyrrolidine-2-carbaldehydes or tetrahydropyridine-2-carbaldehydes from the cascade reactions of N-arylpiperidines or N-arylazepanes is presented. Mechanistically, the formation of the title compounds involves an unprecedented oxidative ring contraction of inactivated cyclic amines via Cu(OAc)2/KI/O2-promoted oxidative cleavage and reformation of the C-N bond. Interestingly, when PhI(OAc)2 was used in place of KI, 1,1-diacetates of the corresponding aldehydes were directly obtained with good efficiency...
January 18, 2018: Organic Letters
https://www.readbyqxmd.com/read/29337556/organocatalyzed-asymmetric-vinylogous-addition-of-oxazole-2-3h-thiones-to-%C3%AE-%C3%AE-unsaturated-ketones-an-additive-free-approach-for-diversification-of-heterocyclic-scaffold
#3
Sandrina Silva, Bianca T Matsuo, Rodrigo C da Silva, Lucas V Pozzi, Arlene G Corrêa, Patrick Rollin, Julio Zukerman-Schpector, Marco Antonio Barbosa Ferreira, Marcio W Paixao
A straightforward organocatalyzed asymmetric addition of oxazole-2(3H)-thiones to α,β-unsaturated ketones is described. This additive-free Michael reaction in the presence of chiral cinchonine-derived primary amines as catalysts have proven to be highly effective for a wide range of cyclic and acyclic enones, leading to the Michael adducts in very good yields and excellent enantioselectivities. The absolute configuration (R) of compound 5j was unambiguous assigned by X-ray diffraction analysis. Furthermore, experimental and theoretical studies were performed and a mechanism is presented and discussed for this novel reaction...
January 16, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29334466/%C3%AE-n-heteroarylation-and-%C3%AE-azidation-of-ketones-via-enolonium-species
#4
Atul More, Gulab K Pathe, Keshaba N Parida, Shimon Maksymenko, Yuriy B Lipisa, Alex Martin Szpilman
Enolonium Species, resulting from the umpolung of ketone enolates by Koser's hypervalent iodine reagents activated by boron trifluoride, react with a variety of nitrogen heterocycles to form α-aminated ketones. The reactions are mild and complete in 4-5 hours. Additionally, α-azidation of the enolonium species takes place using trimethylsilyl azide as a convenient source of azide nucleophile.
January 15, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29334335/simultaneous-formation-of-polycyclic-aromatic-hydrocarbons-pahs-and-heterocyclic-aromatic-amines-hcas-in-gas-grilled-beef-satay-at-different-temperatures
#5
A K Nor Hasyimah, S Jinap, M Sanny
This study investigated the simultaneous formation of polycyclic aromatic hydrocarbons (PAHs) and heterocyclic aromatic amines (HCAs) in gas-grilled beef satay at different temperatures (150°C, 200°C, 250°C, 300°C, and 350°C). Solid-phase extraction (SPE) was used for sample clean-up. Fifteen PAHs were determined using high performance liquid chromatography with fluorescence detection (HPLC-FLD) and nine HCAs were quantified using liquid chromatography tandem-mass spectrometry (LC-MS/MS) with a gradient programme...
January 15, 2018: Food Additives & Contaminants. Part A, Chemistry, Analysis, Control, Exposure & Risk Assessment
https://www.readbyqxmd.com/read/29334224/diversity-oriented-approach-to-n-heterocyclic-compounds-from-%C3%AE-phenyl-%C3%AE-enamino-ester-via-a-mitsunobu-michael-reaction-sequence
#6
Hina P A Khan, Tushar Kanti Chakraborty
Herein we delineate a novel route for the diastereoselective construction of diversely substituted N-heterocyclic ring systems as valuable scaffolds for natural products and pharmaceuticals, starting from easily accessible prochiral α-phenyl-β-enamino ester. The reaction sequence relies on the unexplored reactivity of α-phenyl-β-enamino ester as a nucleophilic partner in Mitsunobu reaction to forge the N-tethered alkene-alcohol/thiol/amine intermediate which was subjected to intramolecular hetero-Michael addition reaction under mild conditions to furnish the respective N-heterocyclic compounds embedded with an exocyclic chiral center in high yields and excellent diastereoselectivities...
January 15, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29332585/new-tacrines-as-anti-alzheimer-s-disease-agents-ii-the-benzo-chromenopyranotacrines
#7
Maria J Oset-Gasque, Jose Marco-Contelles
Tacrine was the first drug approved by FDA (US) for the treatment of Alzheimer's disease suffering patients. Nowadays, this agent has been withdrawn from the clinics due to secondary effects, among them, and the most important, its hepatotoxicity. However, the research on new tacrine analogues devoid of these therapeutically undesirable effects, but benefiting of their high and well known positive cholinergic power, has produced a number of new non-hepatotoxic tacrines. In this context, in our laboratory, in the last years we have prepared a new heterocyclic tacrines by changing the benzene ring present in tacrine by appropriate heterocyclic motifs...
January 12, 2018: Current Topics in Medicinal Chemistry
https://www.readbyqxmd.com/read/29329232/novel-6-and-7-substituted-coumarins-with-inhibitory-action-against-lipoxygenase-and-tumor-associated-carbonic-anhydrase-ix
#8
Aikaterini Peperidou, Silvia Bua, Murat Bozdag, Dimitra Hadjipavlou-Litina, Claudiu T Supuran
A series of carboxamide derivatives of 6- and 7-substituted coumarins have been prepared by an original procedure starting from the corresponding 6- or 7-hydroxycoumarins which were alkylated with ethyl iodoacetate, and the obtained ester was converted to the corresponding carboxylic acids which were thereafter reacted with a series of aromatic/aliphatic/heterocyclic amines leading to the desired amides. The new derivatives were investigated as inhibitors of two enzymes, human carbonic anhydrases (hCAs) and soy bean lipoxygenase (LOX)...
January 12, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/29323905/a-palladium-iodide-catalyzed-oxidative-aminocarbonylation-heterocyclization-approach-to-functionalized-benzimidazoimidazoles
#9
Lucia Veltri, Salvatore V Giofrè, Perry Devo, Roberto Romeo, Adrian P Dobbs, Bartolo Gabriele
A novel carbonylative approach to the synthesis of functionalized 1H-benzo[d]imidazo[1,2-a]imidazoles is presented. The method consists in the oxidative aminocarbonylation of N-substituted-1-(prop-2-yn-1-yl)-1H-benzo[d]imidazol-2-amines, carried out in the presence of secondary nucleophilic amines, to give the corresponding alkynylamide intermediates, followed by in situ conjugated addition and double bond isomerization, to give 2-(1-alkyl-1H-benzo[d]imidazo[1,2-a]imidazol-2-yl)acetamides. Products were obtained in good to excellent yields (64-96%) and high turnover numbers (192-288 mol of product per mol of catalyst) under relatively mild conditions (100 °C under 20 atm of a 4:1 mixture of CO-air), using a simple catalytic system, consisting of PdI2 (0...
January 11, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29323365/iridium-complexes-of-perimidine-based-n-heterocyclic-carbene-pincer-ligands-via-aminal-c-h-activation
#10
Anthony F Hill, Chenxi Ma, Caitlin M A McQueen, Jas S Ward
The reactions of N,N'-bis(phosphinomethyl)dihydroperimidine pro-ligands H2C(NCH2PR2)2C10H6-1,8 (R = Ph 1a, R = Cy 1b) with iridium(i) substrates have been investigated and shown to readily result in chelate-assisted C-H activation processes. The reaction of 1b with [Ir2Cl2(COE)4] (COE = cyclo-octene) affords the 18-electron iridium(iii) dihydrido complex [IrH2Cl{κ3-C,P,P'-C(NCH2PCy2)2C10H6}], which forms [IrHCl2{κ3-C,P,P'-C(NCH2PCy2)2C10H6}] under acidic (HCl) conditions. In contrast, reaction of 1a with [Ir2Cl2(COD)2] (COD = 1,5-cyclo-octadiene) affords the complex [IrCl(COD){κ2-P,P'-H2C(NCH2PPh2)2C10H6}], thermolysis of which affords cyclo-octene and the pincer-NHC complex [IrCl{κ3-C,P,P'-C(NCH2PPh2)2C10H6}]...
January 11, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/29318294/synthesis-and-reduction-of-10-phthalimidocamphor-oxime
#11
Uroš Grošelj, Amalija Golobič, Jurij Svete, Sebastijan Ričko
10-Phthalimidocamphor oxime was prepared from easily available 10-iodocamphor in two steps. Reduction of the oxime functionality resulted in the formation of two novel polycyclic isoindolinone heterocycles, the attempted preparation of the primary amine failed. The structures of novel heterocycles were unambiguously confirmed by single crystal X-ray diffraction as well as NMR techniques.
December 2017: Acta Chimica Slovenica
https://www.readbyqxmd.com/read/29318293/synthesis-of-novel-3d-rich-%C3%AE-amino-acid-derived-3-pyrazolidinones
#12
Jaka Glavač, Georg Dahmann, Franc Požgan, Sebastijan Ričko, Bogdan Štefane, Jurij Svete, Uroš Grošelj
Synthetic approaches towards novel 3-pyrazolidinone derivatives functionalized at positions N(1) and/or C(5) were studied. 5-Aminoalkyl-3-pyrazolidinones were prepared in four steps from N-protected glycines via Masamune-Claisen homologation, reduction, O-mesylation, and cyclisation with a hydrazine derivative. The free amines were prepared by acidolytic deprotection. Title compound was also prepared by 'ring switching' transformation of N-Boc-pyrrolin-2(5H)-one with hydrazine hydrate. Hydrogenolytic deprotection of 5-(N-alkyl-N-Cbz-aminomethyl)pyrazolidine-3-ones followed by cyclisation with 1,1'-carbonyldiimidazole (CDI) gave two novel representatives of perhydroimidazo[1,5-b] pyrazole, which is an almost unexplored heterocyclic system...
December 2017: Acta Chimica Slovenica
https://www.readbyqxmd.com/read/29316301/in-situ-generated-ruthenium-catalytic-systems-bearing-diverse-n-heterocyclic-carbene-precursors-for-the-atom-economic-amide-synthesis-from-alcohols-and-amines
#13
Hua Cheng, Mao-Qian Xiong, Chuan-Xiang Cheng, Hua-Jing Wang, Qiang Lu, Hong-Fu Liu, Fu-Bin Yao, Francis Verpoort, Cheng Chen
The transition-metal-catalyzed direct amide synthesis from alcohols and amines has been demonstrated as a highly environmental-benign and atom-economic process. Among various catalytic systems, in situ generated N-heterocyclic carbene (NHC)-based ruthenium (Ru) halide catalytic systems have been testified to be active for this attractive transformation. However, these existing catalytic systems usually required an additional ligand to achieve satisfactory results. In this work, through extensive screening from a diverse variety of NHC precursors, we discovered an active in situ catalytic system for the efficient amide synthesis without any additional ligand...
January 9, 2018: Chemistry, An Asian Journal
https://www.readbyqxmd.com/read/29311461/-novel-methods-for-the-synthesis-of-heterocycles-using-highly-reactive-spirocyclopropanes
#14
Hisanori Nambu
 This review describes our recent efforts to develop efficient methods for the synthesis of heterocyclic compounds, such as indoles and benzofurans, employing ring-opening cyclization of cyclohexane-1,3-dione-2-spirocyclopropanes, which were prepared by the reaction of 1,3-cyclohexanediones with sulfonium salts. Ring-opening cyclization of cyclohexane-1,3-dione-2-spirocyclopropanes with primary amines proceeded at room temperature to provide 2-substituted tetrahydroindol-4(5H)-ones in good to excellent yield...
2018: Yakugaku Zasshi: Journal of the Pharmaceutical Society of Japan
https://www.readbyqxmd.com/read/29278507/rh-ii-catalyzed-chemoselective-oxidative-amination-and-nucleophilic-trapping-of-gem-dimethyl-alkynyl-tethered-sulfamates
#15
Dong Pan, Yin Wei, Min Shi
A Rh(II)-catalyzed chemoselective oxidative amination and nucleophilic trapping of gem-dimethyl sulfamates has been presented. For 2,2-dimethyl-4-arylbut-3-yn-1-yl sulfamates, the reactions underwent a metallonitrene-initiated alkyne oxidation along with nucleophilic trapping of H2O upon oxidation, giving aroyl group containing heterocycles. For 2,2-dimethyl-4-arylpent-3-yn-1-yl sulfamates, the α-iminometal carbene intermediate was trapped by aryl group migration, delivering a styryl group containing heterocycles...
December 26, 2017: Organic Letters
https://www.readbyqxmd.com/read/29278304/application-of-micro-solid-phase-extraction-for-the-on-site-extraction-of-heterocyclic-aromatic-amines-in-seawater
#16
Chanbasha Basheer
An efficient on-site extraction technique to determine carcinogenic heterocyclic aromatic amines in seawater has been reported. A micro-solid-phase extraction device placed inside a portable battery-operated pump was used for the on-site extraction of seawater samples. Before on-site applications, parameters that influence the extraction efficiency (extraction time, type of sorbent materials, suitable desorption solvent, desorption time and sample volume) were investigated and optimized in the laboratory. The developed method was then used for the on-site sampling of heterocyclic aromatic amines determination in seawater samples close to distillation plant...
December 26, 2017: Journal of Separation Science
https://www.readbyqxmd.com/read/29277623/molecular-mechanistic-pathway-of-colorectal-carcinogenesis-associated-with-intestinal-microbiota
#17
REVIEW
Paramita Mandal
The colon rectal portion of gastrointestinal tract (GI) is full of microorganisms with different complex community that plays important role in maintaining homeostasis. But now-a-days different literature indicated that microbiota cause development of colorectal cancer (CRC) with a disease and ultimately aggravates to death. The mechanism inside the colo-rectal portion of GI tract is not fully well-known and bacterial contribution inside it is also fully unclear. Therefore, there is certain evidence trying a target about the unclear mechanism between intestinal microbiota and CRC...
December 19, 2017: Anaerobe
https://www.readbyqxmd.com/read/29259672/regioselective-decarboxylative-addition-of-malonic-acid-and-its-mono-thio-esters-to-4-trifluoromethylpyrimidin-2-1h-ones
#18
Sergii V Melnykov, Andrii S Pataman, Yurii V Dmytriv, Svitlana V Shishkina, Mykhailo V Vovk, Volodymyr A Sukach
Background: Due to the high reactivity towards various C-nucleophiles, trifluoromethylketimines are known to be useful reagents for the synthesis of α-trifluoromethylated amine derivatives. However, decarboxylative reactions with malonic acid and its mono(thio)esters have been poorly investigated so far despite the potential to become a convenient route to β-trifluoromethyl-β-amino acid derivatives and to their partially saturated heterocyclic analogues. Results: In this paper we show that 4-trifluoromethylpyrimidin-2(1H)-ones, unique heterocyclic ketimines, react with malonic acid under organic base catalysis to regioselectively provide either Michael- or Mannich-type decarboxylative addition products depending on solvent polarity...
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29258340/nat1-genotypic-and-phenotypic-contribution-to-urinary-bladder-cancer-risk-a-systematic-review-and-meta-analysis
#19
Hassan R Dhaini, Bassam El Hafi, Assem M Khamis
N-acetyltransferase 1 (NAT1), a polymorphic Phase II enzyme, plays an essential role in metabolizing heterocyclic and aromatic amines, which are implicated in urinary bladder cancer (BCa). This systematic review investigates a possible association between the different NAT1 genetic polymorphisms and BCa risk. Medline, PubMed, EMBASE, Scopus, Web of Science, OpenGrey, and BASE databases were searched to identify eligible studies. The random-effect model was used to calculate pooled effects estimates. Statistical heterogeneity was tested with Chi-square and I2...
December 19, 2017: Drug Metabolism Reviews
https://www.readbyqxmd.com/read/29250415/crystal-structure-of-cis-1-phenyl-8-pyridin-2-ylmeth-yl-dibenzo-1-2-c-2-1-h-2-14-dioxa-8-aza-1-borabi-cyclo-4-4-0-deca-3-8-diene
#20
Gabriela Ledesma, Sandra Signorella, Davi Back, Ernesto Schulz Lang
The title compound, C26H23BN2O2, was obtained as by product during synthetic attempts of a complexation reaction between the tripodal ligand H2L [N,N-bis-(2-hy-droxy-benz-yl)(pyridin-2-yl)methyl-amine] and manganese(III) acetate in the presence of NaBPh4. The isolated B-phenyl dioxaza-borocine contains an N→B dative bond with a cis conformation. In the crystal, C-H⋯O hydrogen bonds define chains parallel to the b-axis direction. A comparative analysis with other structurally related derivatives is also included, together with a rationalization of the unexpected production of this zwitterionic heterocycle...
December 1, 2017: Acta Crystallographica. Section E, Crystallographic Communications
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