- Hydrogen-bonded molecular capsules: Probing the role of water molecules in capsule formation in modified cyclotricatechylene
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Two new pyridine moiety-appended cavitands, CTC(Py)2(OH)2 and CTC(Py)3, were synthesized and characterized. The solid state structures of both cavitands were studied by single crystal X-ray diffraction. CTC(Py)2(OH)2 resulted in a hydrogen-bonded dimeric molecular capsule, entrapping two molecules of DMSO and intervening water molecules that formed hydrogen bonding to DMSO and CTC(Py)2(OH)2. When crystallized in the absence of water, it forms a 2D polymer by hydrogen bonding of pyridine nitrogen and phenolic hydrogen atoms. CTC(Py)3 forms no such capsule.
- Illa, Giri Teja,Hazra, Sohan,Satha, Pardhasaradhi,Purohit, Chandra Shekhar
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- Ferric chloride hexahydrate: A convenient reagent for the oxidation of hantzsch 1,4-dihydropyridines
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A general and practical route for the moderate yield oxidative conversion of readily accessible 1,4-dihydropyridines (1,4-DHPs) to the corresponding pyridines was described using a relatively benign oxidant, i.e. ferric chloride hexahydrate (FeCl3·6H2O). The reaction was carried out under mild and convenient condition. However, oxidation of 4-isopropyl-1,4-DHP 1b with FeCl3·6H2O afforded the dealkylated pyridine 2a.
- Lu,Bai,Wang,Yang,Li
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- Synthesis of the pyridine hydrazones as metal-free artificial nucleases
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In this report, four pyridine hydrazones containing anthracene and triphenylamine as a new type of metal-free nucleases were synthesized. Results indicate that the conjugates can cleave the plasmid DNA to Form II or Form III under physiological conditions via hydrolytic pathway.
- Li, Zhifen,Qiao, Jun,Jia, Zhifang,Meng, Shuangming
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- Oxidative aromatization of hantzsch 1,4-dihydropyridines by H 2O2/V2o5 at room temperature
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A mild and highly efficient synthetic method was developed for the aromatization of 1,4-dihydropyridines employing H2O2 and 5mol% of V2O5. The reactions were carried out in CH 3CN to give pyridine compounds in excellent yields. Copyright Taylor & Francis Group, LLC.
- Su, Jinlong,Zhang, Cai,Lin, Dan,Duan, Yiqin,Fu, Xiangkai,Mu, Ruizhu
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- Rhodium-Catalyzed Diastereo- And Enantioselective Tandem Spirocyclization/Reduction of 3-Allenylindoles: Access to Functionalized Vinylic Spiroindolines
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A highly selective rhodium-catalyzed tandem spirocyclization/reduction of 3-allenylindoles is reported. By employing a Hantzsch ester as reductant, vinylic spiroindolines are obtained in excellent yields as well as diastereo- and enantioselectivity. In addition, the reaction's synthetic utility is highlighted by broad functional group compatibility and exemplified by a gram scale reaction with subsequent assorted transformations.
- Grugel, Christian P.,Breit, Bernhard
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- Slow generation of hydrogen sulfide from sulfane sulfurs and NADH models
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Here we report the model studies of the reactions between NADH models (using HEH and BNAH) and sulfane sulfurs (using polysulfides). Such reactions could lead to the oxidation of NADH models and the production of hydrogen sulfide (H2S). Kinetics of the reaction between BNAH and elemental sulfur S8were determined in ethanol and the second-order rate constant was found to be 0.074?M?1?min?1(at 37?°C) suggesting this is a slow process.
- Peng, Bo,Liu, Chunrong,Li, Zhen,Day, Jacob J.,Lu, Yun,Lefer, David J.,Xian, Ming
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- Formic acid disproportionation into formaldehyde triggered by vanadium complexes with iridium catalysis under mild conditions inN-methylation
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Formaldehyde (CH2O) has been used as a key platform reagent in the chemical industry for many decades. Currently, the industrial production of CH2O mainly depends on fossil resources, involving a highly energetic three-step process (200-1100 °C). Herein, we describe renewable formic acid (HCO2H) disproportionation into CH2O triggered by vanadium complexes with iridium catalysis under mild conditions at 30-50 °C inN-methylation. The gram-scale application ofin situgenerated CH2O by HCO2H disproportionation is demonstrated.
- Guo, Yan-Jun,Li, Yang,Zhang, Ping,Zhao, Yu-Rou,Zhou, Chao-Zheng
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- Evaluation of Organic Hydride Donors as Reagents for the Reduction of Carbon Dioxide and Metal-Bound Formates
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A variety of organic hydride donors (OHDs) have been tested as reagents for the transfer of hydride to iron formato complexes in the activation and reduction of carbon dioxide. Theoretical calculations show that the selection of OHD and solvent is crucial when planning systems involving OHD cooperativity. Strong consideration is given to the likelihood that metal centers may deactivate formate to hydride attack, since, in general, the formate group has more resonance stabilization energy when complexed to a metal center compared to an organoformate or formic acid. It is experimentally demonstrated that 1,2-dihydropyridine is not a competent reducing agent for carbon dioxide.
- Elton, Timothy E.,Ball, Graham E.,Bhadbhade, Mohan,Field, Leslie D.,Colbran, Stephen B.
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- Late-Stage C-H Alkylation of Heterocycles and 1,4-Quinones via Oxidative Homolysis of 1,4-Dihydropyridines
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Under oxidative conditions, 1,4-dihydropyridines (DHPs) undergo a homolytic cleavage, forming exclusively a Csp3-centered radical that can engage in the C-H alkylation of heterocyclic bases and 1,4-quinones. DHPs are readily prepared from aldehydes, and considering that aldehydes normally require harsh reaction conditions to take part in such transformations, with mixtures of alkylated and acylated products often being obtained, this net decarbonylative alkylation approach becomes particularly useful. The present method takes place under mild reaction conditions and requires only persulfate as a stoichiometric oxidant, making the procedure suitable for the late-stage C-H alkylation of complex molecules. Notably, structurally complex pharmaceutical agents could be functionalized or prepared with this protocol, such as the antimalarial Atovaquone and antitheilerial Parvaquone, thus evidencing its applicability. Mechanistic studies revealed a likely radical chain process via the formation of a dearomatized intermediate, providing a deeper understanding of the factors governing the reactivity of these radical forebears.
- Gutiérrez-Bonet, álvaro,Remeur, Camille,Matsui, Jennifer K.,Molander, Gary A.
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- One-pot synthesis of 3-hydroxy-2-oxindole-pyridine hybrids via Hantzsch ester formation, oxidative aromatization and sp3 C–H functionalization using FeWO4 nanoparticles as recyclable heterogeneous catalyst
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Synthesis of poly-substituted 3-hydroxy-2-oxindole-pyridine hybrids is reported via sp3 C–H bond functionalization as key steps using FeWO4 nanoparticles as reusable heterogeneous catalyst. Formation of Hantzsch ester (DHP) followed by aromatization, and sp3 C–H bond functionalization was achieved using FeWO4 nanoparticles (20 mol%) at 80 °C. Temperature dependent reactivity was observed for mono aldol (at 80 °C) and bis aldol (at 120 °C) products. The catalyst was regenerated and reused up to 6 cycles without losing catalytic activity. The FeWO4 nanoparticles were also used for oxidative aromatization of different DHP derivatives and for the sp3 C–H functionalization of 2-methyl pyridine.
- Paplal, Banoth,Nagaraju, Sakkani,Sathish, Kota,Kashinath, Dhurke
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- Batch and continuous flow preparation of hantzsch 1,4-dihydropyridines under microwave heating and simultaneous real- Time monitoring by raman spectroscopy. An exploratory study
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Dialkyl 1,4-dihydro-2,6-dimethylpyridine-3,5-dicarboxylates have been prepared in a batch mode under conventional heating as well as under continuous flow conditions in the Miniflow 200SS, Sairem's microwave- Assisted batch and continuous flow equipment. Real- Time monitoring of the reactions by Raman spectroscopy enabled to compare both heating modes and to determine (optimized) reaction times.
- Christiaens, Sylvain,Vantyghem, Xavier,Radoiu, Marilena,Eynde, Jean Jacques Vanden
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- Aqueous CO2fixation: construction of pyridine skeletons in cooperation with ammonium cations
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A simple and green method is explored for the synthesis of fused pyridines by [2 + 2 + 1 + 1] the cycloaddition of ketones with an ammonium cation under a CO2atmosphere. The reactions employed ammonium cation as a nitrogen source and CO2gas as a carbon source in an aqueous solution. Monoethanolamine (MEA) was used as an additive to increase the solubility of CO2in an aqueous solution. The scope and versatility of the method are demonstrated with 38 examples. Products are found to be photosensitive and show potential applications as organic optoelectronic materials. A selectfluor-promoted reaction mechanism is proposed based on the experimental studies. Our work is superior as it is a metal-free system, uses CO2as a carbon source and MEA as an additive in aqueous synthesis.
- Fan, Weibin,Guo, Shiwei,Huang, Deguang,Li, Yinghua,Xiang, Shiqun,Zhang, Wei
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supporting information
p. 7950 - 7955
(2021/10/29)
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- Reductive Alkylation of Quinolines to N-Alkyl Tetrahydroquinolines Catalyzed by Arylboronic Acid
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A boronic acid catalyzed one-pot tandem reduction of quinolines to tetrahydroquinolines followed by reductive alkylation by the aldehyde has been demonstrated. This step-economcial synthesis of N-alkyl tetrahydroquinolines has been achieved directly from readily available quinolines, aldehydes, and Hantzsch ester under mild reaction conditions. The mechanistic study demonstrates the unique behavior of organoboron catalysts as both Lewis acids and hydrogen-bond donors.
- Adhikari, Priyanka,Bhattacharyya, Dipanjan,Nandi, Sekhar,Kancharla, Pavan K.,Das, Animesh
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supporting information
p. 2437 - 2442
(2021/04/05)
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- A Titanium-Catalyzed Reductive α-Desulfonylation
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A titanium(III)-catalyzed desulfonylation gives access to functionalized alkyl nitrile building blocks from α-sulfonyl nitriles, circumventing traditional base-mediated α-alkylation conditions and strong single electron donors. The reaction tolerates numerous functional groups including free alcohols, esters, amides, and it can be applied also to the α-desulfonylation of ketones. In addition, a one-pot desulfonylative alkylation is demonstrated. Preliminary mechanistic studies indicate a catalyst-dependent mechanism involving a homolytic C?S cleavage.
- Kern, Christoph,Selau, Jan,Streuff, Jan
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supporting information
p. 6178 - 6182
(2021/03/16)
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- Organocatalytic epoxidation and allylic oxidation of alkenes by molecular oxygen
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Pyrrole-proline diketopiperazine (DKP) acts as an efficient mediator for the reduction of dioxygen by Hantzsch ester under mild conditions to allow the aerobic metal-free epoxidation of electron-rich alkenes. Mechanistic crossovers are underlined, explaining the dual role of Hantzsch ester as a reductant/promoter of the DKP catalyst and a simultaneous competitor for the epoxidation of alkenes when HFIP is used as a solvent. Expansion of this protocol to the synthesis of allylic alcohols was achieved by adding a catalytic amount of selenium dioxide as an additive, revealing a superior method to the classical application of t-BuOOH as a selenium dioxide oxidant.
- Orfanidou, Maria,Petsi, Marina,Zografos, Alexandros L.
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supporting information
p. 9172 - 9178
(2021/11/30)
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- Boric acid catalyzed chemoselective reduction of quinolines
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Boric acid promoted transfer hydrogenation of substituted quinolines to synthetically versatile 1,2,3,4-tetrahydroquinolines (1,2,3,4-THQs) was described under mild reaction conditions using a Hantzsch ester as a mild organic hydrogen source. This methodology is practical and efficient, where isolated yields are excellent and reducible functional groups are well tolerated in the N-heteroarene moiety. The reaction parameters and tentative mechanistic pathways are demonstrated by various control experiments and NMR studies. The present work can also be scaled up to obtain gram quantities and the utility of the developed process is illustrated by the transformation of 1,2,3,4-THQs into a series of biologically important molecules including the antiarrhythmic drug nicainoprol.
- Adhikari, Priyanka,Bhattacharyya, Dipanjan,Das, Animesh,Konwar, Monuranjan,Nandi, Sekhar,Sarmah, Bikash Kumar
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supporting information
p. 1214 - 1220
(2020/02/22)
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- σ-Bond initiated generation of aryl radicals from aryl diazonium salts
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σ-Bond nucleophiles and molecular oxygen transform aryl diazonium salts into aryl radicals. Experimental and computational studies show that Hantzsch esters transfer hydride to aryl diazonium species, and that oxygen initiates radical fragmentation of the diazene intermediate to produce aryl radicals. The operational simplicity of this addition-fragmentation process for the generation of aryl radicals, by a polar-radical crossover mechanism, has been illustrated in a variety of bond-forming reactions.
- Chan, Bun,McErlean, Christopher S. P.,Nashar, Philippe E.,Tatunashvili, Elene
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supporting information
p. 1812 - 1819
(2020/03/17)
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- Preparation method of dihydropyridine crude drug
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The invention relates to a preparation method of a dihydropyridine crude drug. The preparation method of the dihydropyridine crude drug comprises the following steps: feeding ethyl acetoacetate and urotropine in a reactor, and mixing and dissolving at the temperature of 15-20 DEG C; slowly dropwise adding ethanol amine, and after dropwise adding is finished, carrying out heating and refluxing reaction; carrying out cooling crystallization and centrifuging to obtain a dihydropyridine crude product; adding ethanol and the dihydropyridine crude product in a refining kettle, heating, stirring anddissolving, regulating PH to be neutral by using glacial acetic acid, then adding activated carbon, stirring for 1 hour, and then pressing into a crystallization kettle; and carrying out cooling crystallization and centrifuging, and drying under vacuum to obtain the dihydropyridine crude drug. An organic solvent is not used in a reaction process, the preparation method is simple to operate, environmental pollution is low, reaction conditions are mild, the safety is high, the cost is low, the quality of products is good, and industrialization is facilitated.
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Paragraph 0017-0023
(2019/02/27)
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- Metal free biomimetic deaminative direct C-C coupling of unprotected primary amines with active methylene compounds
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An unprecedented direct C-C coupling reaction of unprotected primary amines with active methylene compounds is reported. The reaction involves a biomimetic deamination of amines which was achieved under conditions free of metallic reagents and strong oxidizing agents. A wide range of primary amines was reacted with different active methylene compounds to provide structurally diverse trisubstituted alkenes and dihydropyridines. A kinetic study revealed an activation barrier of 10.1 kcal mol-1 for the conversion of a key intermediate of the reaction.
- Ghosh, Santanu,Jana, Chandan K.
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supporting information
p. 10153 - 10157
(2019/12/26)
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- MIL-101-SO3H metal-organic framework as a Br?nsted acid catalyst in Hantzsch reaction: An efficient and sustainable methodology for one-pot synthesis of 1,4-dihydropyridine
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A straightforward and efficient methodology for the one-pot multicomponent synthesis of 1,4-dihydropyridine has been developed using MIL-101-SO3H metal-organic framework as a solid Br?nsted acid. The presence of the uniformly distributed Br?nsted acidic sulfonic acid sites throughout the framework and the high stability bestow the catalyst with excellent reactivity towards the synthesis of 1,4-dihydropyridine under simple reaction conditions using renewable ethanol as the solvent. The present methodology tolerates various functional groups and allows the synthesis of 1,4-dihydropyridine derivatives in good to excellent yields through Hantzsch reaction. The developed methodology proceeds under mild conditions, avoids corrosive reagents and special reaction conditions, and is amenable to gram scale synthesis. The sustainable nature of the catalyst was proved by the easy recovery and the reusability of the catalyst, as it was reused several times without loss in activity, which was confirmed from the FTIR, PXRD and SEM analyses of the reused catalyst.
- Devarajan, Nainamalai,Suresh, Palaniswamy
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p. 6806 - 6814
(2019/05/10)
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- Synergistic catalytic effect between ultrasound waves and pyrimidine-2,4-diamine-functionalized magnetic nanoparticles: Applied for synthesis of 1,4-dihydropyridine pharmaceutical derivatives
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A convenient strategy for synthesis of the various derivatives of 1,4-dihydropyridine (1,4-DHP), as one of the most important pharmaceutical compounds, is presented in this study. For this purpose, firstly, magnetic iron oxide nanoparticles (Fe3O4 NPs) were fabricated and suitably coated by silica network (SiO2) and trimethoxy vinylsilane (TMVS). Then, their surfaces were well functionalized with pyrimidine-2,4-diamine (PDA) as the main active sites for catalyzing the synthesis reactions. In this regard, the performance of three different methods including reflux, microwave (MW) and ultrasound wave (USW) irradiations have been comparatively monitored via studying various analyses on the fabricated nanocatalyst (Fe3O4/SiO2-PDA). Concisely, high efficiency of the USW irradiation (in an ultrasound cleaning bath with a frequency of 50 kHz and power of 250 W/L) has been well proven through the investigation of the main factors such as excellent surface-functionalization, core/shell structure conservation, particle uniformity, close size distribution of the particles, and great inhibition of the particle aggregation. Then, the effectiveness of the USW irradiation as a promising co-catalyst agent has been clearly demonstrated in the 1,4-DHP synthesis reactions. It has been concluded that the USW could provide more appropriate conditions for activation of the catalytic sites of Fe3O4/SiO2-PDA NPs. However, high reaction yields (89%) have been obtained in the short reaction times (10 min) due to the substantial synergistic effect between the presented nanocatalyst and USW.
- Taheri-Ledari, Reza,Rahimi, Jamal,Maleki, Ali
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- Titanium(III)-Catalyzed Reductive Decyanation of Geminal Dinitriles by a Non-Free-Radical Mechanism
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A titanium-catalyzed mono-decyanation of geminal dinitriles is reported. The reaction proceeds under mild conditions, tolerates numerous functional groups, and can be applied to quaternary malononitriles. A corresponding desulfonylation is demonstrated as well. Mechanistic experiments support a catalyst-controlled cleavage without the formation of free radicals, which is in sharp contrast to traditional stoichiometric radical decyanations. The involvement of two TiIII species in the C?C cleavage is proposed, and the beneficial role of added ZnCl2 and 2,4,6-collidine hydrochloride is investigated.
- Weweler, Jens,Younas, Sara L.,Streuff, Jan
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supporting information
p. 17700 - 17703
(2019/11/13)
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- Organocatalyzed biomimetic selective reduction of c=c double bonds of chalcones
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In this article, we reported a biomimetic approach for chemoselective reduction of C=C double bonds in chalcones under metal and acid free conditions, that relies on olefin activation by hydrogen bond formation. The process requires only catalytic amount of ephedrine as hydrogen bond donor and utilizes Hantzsch esters for transfer hydrogenation.
- Tripathi, Vishwa Deepak,Jha, Anand Mohan
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p. 2322 - 2324
(2018/09/09)
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- Asymmetric Synthesis of Carbocyclic Propellanes
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A modular synthesis of functionalized carbocyclic propellanes was developed. Formation of the first of two quaternary bridgehead centers has been achieved by desymmetrization of prostereogenic ketones by either Hajos-Parrish-Eder-Sauer-Wiechert-type processes or Werner’s catalytic asymmetric Wittig reaction. The obtained bicyclic enones were subjected to conjugate additions upon which the remaining ring was formed by olefin metathesis. All bridges are amenable to further derivatization, which renders those compounds useful as central units in fragment-based drug discovery or as ligand scaffolds.
- Schneider, Lisa M.,Schmiedel, Volker M.,Pecchioli, Tommaso,Lentz, Dieter,Merten, Christian,Christmann, Mathias
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supporting information
p. 2310 - 2313
(2017/05/12)
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- Sulfated polyborate: An efficient and reusable catalyst for one pot synthesis of Hantzsch 1,4-dihydropyridines derivatives using ammonium carbonate under solvent free conditions
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A simple and efficient method for the synthesis of four-component 1,4-dihydropyridines of various aldehydes, β-ketoesters and ammonium carbonate catalyzed by sulfated polyborate with high yields under a solvent free condition at 90?°C is described. The key advantages of the present method are high yields, short reaction time, solvent free condition, easy workup, recyclability of catalyst and ability to tolerate a variety of functional groups which gives economical as well as ecological rewards.
- Rekunge, Deelip S.,Khatri, Chetan K.,Chaturbhuj, Ganesh U.
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supporting information
p. 1240 - 1244
(2017/03/02)
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- Photoredox-Catalyzed Hydrodifluoroalkylation of Alkenes Using Difluorohaloalkyl Compounds and a Hantzsch Ester
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Photoredox-catalyzed hydrodifluoroalkylation of alkenes proceeded smoothly in the presence of a Hantzsch ester as a hydrogen source under visible light irradiation. The reaction was also applicable to the hydrodifluoroalkylation of alkynes, and a continuous photo flow reaction was also successful.
- Sumino, Shuhei,Uno, Misae,Fukuyama, Takahide,Ryu, Ilhyong,Matsuura, Makoto,Yamamoto, Akinori,Kishikawa, Yosuke
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p. 5469 - 5474
(2017/05/24)
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- Syntheses, Structural Characterization, Reactivity, and Theoretical Studies on Some Heteroligand Oxoperoxotungstate(VI)
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White microcrystalline diamagnetic oxoperoxotungstate(VI) complexes K[WO(O2)2F]·H2O, K2[WO(O2)2(CO3)]·H2O, [WO(O2)(SO4)(H2O)2] have been synthesized from reaction of Na2WO4·2H2O with aqueous HF, solid KHCO3, aqueous H2SO4 (W:F? 1:3; W: CO3 2 ? 1:1; and W: SO4 2 ? 1:3), and an excess of 30% H2O2 at pH 7.5–8. Precipitation was completed by the addition of precooled acetone. The occurrence of terminal W?O and triangular bidentate O2 2 ?(C 2 v) in the synthesized compounds was ascertained from IR spectra. The IR spectra also suggested that the F? and SO4 2 ? ions in K[WO(O2)2F]·H2O and [WO(O2)(SO4)(H2O)2] were bonded to the WO +4 center in monodentate manner, while CO3 2 ? ion in K2[WO(O2)2(CO3)]·H2O binds the metal center in bidentate chelating fashion. The complex [WO(O2)(SO4)(H2O)2] is stable upto 110°C. The water molecule in [WO(O2)(SO4)(H2O)2] is coordinated to the WO +4 center, whereas it occurs as water of crystallization in the corresponding peroxo(fluoro) and peroxo(carbonato) compounds. Mass spectra of the compounds are in good agreement with the molecular formulae of the complexes. K2[WO(O2)2(CO3)]·H2O acts as an oxidant for bromide in the aqueous-phase bromination of organic substrates to the corresponding bromo-organics, and the complex also oxidizes Hantzsch-1,4-dihydropyridine to the corresponding pyridine derivative in excellent yield at room temperature. Density functional theory computation was carried out to compute the frequencies of relevant vibrational modes and electronic properties, and the results are in agreement with the experimentally obtained data.
- Das, Nandita,Chowdhury, Shubhamoy,Dutta Purkayastha, Ranendra N.
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- Intermolecular [2 + 2] Cycloaddition of 1,4-Dihydropyridines with Olefins via Energy Transfer
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A highly regio- and diastereoselective visible-light-promoted [2 + 2] cycloaddition between readily available 1,4-dihydropyridines and olefins has been developed. This strategy is operationally simple and atom-economical and enables the construction of strained polysubstituted 2-azabicyclo[4.2.0]octanes with three all-carbon quaternary centers with good functional group tolerance. These products can be easily converted to various structurally unique derivatives. The primary mechanistic studies demonstrated that the reaction proceeds through an energy transfer pathway.
- Wang, Chengfeng,Lu, Zhan
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supporting information
p. 5888 - 5891
(2017/11/10)
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- Mitochondria-targeted dihydropyridine derivative as well as preparation method and application thereof
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The invention discloses a preparation method and application of a mitochondria-targeted dihydropyridine compound. The mitochondria-targeted dihydropyridine compound has structures of a formula (I) and a formula (II) (shown in the description). Experiments prove that the mitochondria-targeted dihydropyridine compound is capable of effectively eliminating reactive oxygen species (ROS) generated by ionization radiation and therefore can be applied to the treatment of free radical-induced relevant diseases such as Alzheimer's disease and ionization damage disease. The preparation method is simple, and the product is easily prepared and pollution-free.
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Paragraph 0038
(2017/10/13)
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- Synthesis and radioprotective activity of mitochondria targeted dihydropyridines in vitro
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The radiation-induced damage to mitochondrial oxidative respiratory chain could lead to generating of superoxide anions (O2-) and secondary reactive oxygen species (ROS), which are the major resources of continuous ROS production after radiation. Scavenging radiation-induced ROS effectively can help mitochondria to maintain their physiological function and relief cells from oxidative stress. Dihydropyridines (DHPs) are biomimetic hydrogen sources that could protect cells against radiation damage. In this study, we designed and synthetized three novel mitochondrial-targeted dihydropyridines (Mito-DHPs) that utilize the mitochondrial membrane potential to enter the organelle and scavenge ROS. MitoTracker confirmed Mito-DHPs accumulation in mitochondria, and the DCFH-DA assay demonstrated effective ROS scavenging activity. In addition, the γ-H2AX and comet assay demonstrated the ability of Mito-DHPs to protect against both radiation and ROS-induced DNA strand breaks. Furthermore, Mito-DHP1 proved to be non-toxic and displayed significant radioprotection activity (p 0.05) in vitro. Mito-DHPs are therefore promising antioxidants that could penetrate the membrane of mitochondria, scavenge excessive ROS, and protect cells against radiation-induced oxidative damage.
- Zhang, Yurui,Wang, Junying,Li, Yuanyuan,Wang, Feng,Yang, Fujun,Xu, Wenqing
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- One-Pot Synthesis of Hantzsch Pyridines via NH4I Promoted Condensation of 1,3-Dicarbonyl Compounds with DMSO and NH4OAc
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A one-pot synthesis of Hantzsch pyridines was achieved through NH4I-promoted condensation of 1,3-dicarbonyl compounds with DMSO and NH4OAc, in which the C4 of the pyridine rings was derived from DMSO and the nitrogen atom resulted from NH4OAc and NH4I. The target product could be obtained in moderate to excellent yields.
- Chang, Liming,Lai, Junyi,Yuan, Gaoqing
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p. 887 - 894
(2016/09/20)
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- Tetraethylammonium 2-(carbamoyl)benzoate as a bifunctional organocatalyst for one-pot synthesis of Hantzsch 1,4-dihydropyridine and polyhydroquinoline derivatives
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Abstract: A green, convenient, and environment-friendly approach for the synthesis of biologically active Hantzsch 1,4-dihydropyridine and polyhydroquinoline derivatives in the presence of tetraethylammonium 2-(carbamoyl)benzoate, as an effective bifunctional metal-free catalyst, has been developed via a one-pot multicomponent reaction of various aldehydes, ethyl acetoacetate or cyclic 1,3-dicarbonyl compounds, and ammonium acetate in EtOH under reflux conditions. The proposed methodology is capable of providing the desired products in good to excellent yields and short reaction time with straightforward work-up and a low-cost procedure. Graphical abstract: [Figure not available: see fulltext.]
- Yarhosseini, Mahsa,Javanshir, Shahrzad,Dekamin, Mohammad G.,Farhadnia, Mohammad
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p. 1779 - 1787
(2016/09/28)
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- Selective Debromination and α-Hydroxylation of α-Bromo Ketones Using Hantzsch Esters as Photoreductants
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Two transformations initiated by photoinduced one-electron transfer to α-bromo ketones have been demonstrated. Hantzsch esters donate one electron to α-bromo ketones under photoirradiation, promoting reductive debromination. Subsequent reactions of the resulting radical species of the ketones with molecular oxygen and Hantzsch esters lead to α-hydroxylation or debromination, respectively. The relative dominance of the two pathways depends profoundly on the reaction conditions, including solvent, O2 levels, and the concentration of the Hantzsch esters. The synthetic protocols feature advantages because they require the environmentally benign sources, molecular oxygen and visible light.
- Jung, Jaehun,Kim, Jun,Park, Gyurim,You, Youngmin,Cho, Eun Jin
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supporting information
p. 74 - 80
(2016/01/25)
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- Benzyltrimethylammoniumfluoride Hydrate: An Efficient Catalyst for One-Pot Synthesis of Hantzsch 1,4-Dihydropyridines and Their Aromatization
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An efficient, cost-effective and simple protocol has been developed for the synthesis of Hantzsch 1,4-dihydropyridines and their oxidation into pyridines using benzyltrimethylammonium fluoride hydrate as an excellent catalyst under solvent-free condition. All of the products synthesized by this method are characterized by various spectroscopic methods (IR, 1H NMR, 13C NMR, and DEPT).
- Khaskel, Anamika,Barman, Pranjit
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p. 114 - 120
(2016/04/01)
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- Simple Br?nsted acid catalyzed C-H functionalization: Efficient access to poly-substituted pyridines
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An exceptionally simple and environmentally friendly methodology has been developed for directly functionalizing the benzylic C-H bond of the poly-substituted pyridines with aromatic imines. Simple Br?nsted acid catalysts including salicylic acid and TsOH were successfully employed. Different types of poly-substituted pyridines could be efficiently obtained with moderate yields. Traditional ways to such types of pyridines involved the aromatization of the corresponding Hantzsch 1,4-dihydropyridines, while this method greatly simplified the synthetic procedures.
- Lai, Shujun,Ren, Xuwen,Zhao, Jinzhong,Tang, Zhuo,Li, Guangxun
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supporting information
p. 2957 - 2961
(2016/07/06)
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- USE OF COMPOSITIONS OBTAINED BY CALCINING PARTICULAR METAL-ACCUMULATING PLANTS FOR IMPLEMENTING CATALYTICAL REACTIONS
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The use of metal-accumulating plants for implementing chemical reactions especially catalytical reactions.
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Paragraph 0849-0850
(2016/01/25)
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- Silica functionalized sulphonic acid coated with ionic liquid: An efficient and recyclable heterogeneous catalyst for the one-pot synthesis of 1,4-dihydropyridines under solvent-free conditions
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Silica-supported sulphonic acid catalysts were prepared and coated with ionic liquid, and their catalytic activities were evaluated for the one-pot synthesis of 1,4-dihydropyridines. Different catalysts with an ionic liquid layer (SCILLs) have been prepared with a view to determine the most active catalyst. Silica sulphonic acid coated with [BMIM][PF6] was found to be the most active catalyst and can be recycled for several runs without the loss of significant activity. It was characterized using SEM, TEM, TGA and FTIR.
- Sharma, Pankaj,Gupta, Monika
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p. 1100 - 1106
(2015/03/04)
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- One-Pot Three-Component Synthesis of Hantzsch 1,4-Dihydropyridines Promoted by Dimethyl Phosphate Ionic Liquids
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A one-pot three-component reaction of ethyl acetoacetate, AcONH4, and different aldehydes has been successfully performed in the presence of ionic liquids (ILs) possessing a (MeO)2PO2- counterion. The impact of electronic and steric effects of the substituents of aromatic aldehydes, as well as the influence of different anions of ILs on the product yield, have been investigated. The application of dimethyl phosphate ILs in the synthesis of Hantzsch 1,4-dihydropyridines presents a simple method for obtaining structurally diverse products in moderate to high yields without using any additional catalyst.
- Priede, Elina,Zicmanis, Andris
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p. 1095 - 1103
(2015/08/24)
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- Photoinduced proton transfer promoted by peripheral subunits for some Hantzsch esters
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It is noted that, for a small series of 3,5-diacetyl-1,4-dihydrolutidine (DDL) derivatives and the corresponding Hantzsch esters, the presence of methyl groups at the 2,6-positions serves to extinguish fluorescence in solution but not in the solid state. Emission is weakly activated and affected by changes in solvent polarity. The latter situation arises because the optical transition involves intramolecular charge transfer. Calculations, both semiempirical and DFT, indicate that, in all cases, rotation of the carbonyl function is facile and that the dihydropyridine ring is planar. These calculations also indicate that the 2,6-methyl groups do not affect the generic structure of the molecule. It is proposed that illumination increases the molecular dipole moment and pushes electron density toward the carbonyl oxygen atom. Proton transfer can now occur from one of the methyl groups, leading to formation of a relatively low-energy, neutral intermediate, followed by a second proton transfer step that forms the enol. Reaction profiles computed for the ground-state species indicate that this route is highly favored relative to hydrogen transfer from the 4-position. The barriers for light-induced proton transfer are greatly reduced relative to the ground-state process but such large-scale structural transformations are hindered in the solid state. A rigid analogue that cannot form an enol is highly emissive in solution, supporting the conclusion that proton transfer is in competition to fluorescence in solution. (Figure Presented).
- Azizi, Sbastien,Ulrich, Gilles,Guglielmino, Maud,Le Calv, Stphane,Hagon, Jerry P.,Harriman, Anthony,Ziessel, Raymond
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- Synthesis of Functionalized 1H-Isochromene Derivatives via a Au-Catalyzed Domino Cycloisomerization/Reduction Approach
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A Au-catalyzed versatile and efficient access to 1H-isochromenes is reported. The efficiency of the [AuCl2(Pic)] complex (1-5 mol %) was demonstrated and allowed a domino cycloisomerization/reduction reaction process starting from a wide range of functionalized ortho-alkynylbenzaldehydes and one example of ortho-alkynylpyridinylaldehyde. The smooth reaction conditions were amenable to aryl- and alkyl-substituted alkynyl derivatives, as well as functionalized halogen and ether moieties, leading to a chemo- and regioselective 6-endo-cyclization with good to excellent yields.
- Tomás-Mendivil, Eder,Starck, Jéro?me,Ortuno, Jean-Claude,Michelet, Véronique
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supporting information
p. 6126 - 6129
(2016/01/09)
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- Phosphothreonine as a Catalytic Residue in Peptide-Mediated Asymmetric Transfer Hydrogenations of 8-Aminoquinolines
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Phosphothreonine (pThr) was found to constitute a new class of chiral phosphoric acid (CPA) catalyst upon insertion into peptides. To demonstrate the potential of these phosphopeptides as asymmetric catalysts, enantioselective transfer hydrogenations of a previously underexplored substrate class for CPA-catalyzed reductions were carried out. pThr-containing peptides lead to the observation of enantioselectivities of up to 94:6 e.r. with 2-substituted quinolines containing C8-amino functionality. NMR studies indicate that hydrogen-bonding interactions promote strong complexation between substrates and a rigid β-turn catalyst.
- Shugrue, Christopher R.,Miller, Scott J.
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supporting information
p. 11173 - 11176
(2016/07/06)
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- Alginic acid: A highly efficient renewable and heterogeneous biopolymeric catalyst for one-pot synthesis of the Hantzsch 1,4-dihydropyridines
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Alginic acid, a naturally occurring polysaccharide, in its granular form and without any post-modification was found to be an efficient, environmentally benign, easily recoverable and low-cost catalyst for the clean and rapid synthesis of 1,4-dihydropiridine derivatives (DHPs) just based on its polysaccharide architecture. The Hantzsch pseudo-four-component reaction of ethyl or methyl acetoacetate, ammonium acetate and different aldehydes is catalyzed by alginic acid efficiently under mild conditions to afford the desired products in high to quantitative yields and clean reaction profiles. Avoiding the use of any transition metal, the use of a one-pot and multi-component procedure for the synthesis of DHPs, the reusability of the catalyst and operational simplicity are important features of this methodology.
- Dekamin, Mohammad G.,Ilkhanizadeh, Siamand,Latifidoost, Zahra,Daemi, Hamed,Karimi, Zahra,Barikani, Mehdi
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p. 56658 - 56664
(2015/02/02)
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- Recyclable Bi2WO6-nanoparticle mediated one-pot multicomponent reactions in aqueous medium at room temperature
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Different types of multicomponent reactions (MCRs) are reported using Bi2O3, BiVO4, and Bi2WO6 (nanoparticle) as heterogeneous catalysts. Among these, Bi2WO6 nanoparticles showed excellent reactivity for the synthesis of functionalized dihydropyridine, polyhydroquinoline, 4H-chromene and 2-amino-4H-benzo[b]pyran derivatives at ambient temperature in aqueous medium. All the reactions gave good to excellent yields in 10-45 minutes in the presence of 5 mol% (optimized) of the catalyst. The catalyst was regenerated and reused up to 5 times without losing catalytic activity. The gram scale synthesis of dihydropyridine gave the desired product in 82% yield in 2 h. This journal is
- Paplal, Banoth,Nagaraju,Veerabhadraiah, Palakollu,Sujatha, Kodam,Kanvah, Sriram,Vijaya Kumar,Kashinath, Dhurke
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p. 54168 - 54174
(2015/02/18)
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- Task-specific ionic liquid incorporating anionic heteropolyacid-catalyzed Hantzsch and Mannich multicomponent reactions. Ionic liquid effect probed by ESI-MS(/MS)
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A task-specific ionic liquid with a Bronsted acid (1-(3-sulfopropyl)-3- methylimidazolium hydrogen sulfate, namely MSI) bearing an anionic heteropolyacid derivative ([PW12O40]3-, namely PW) were used as an efficient catalyst for the three-component Mannich and Hantzsch reactions. Using (MSI)3PW as the catalyst supported in imidazolium-based ionic liquids allowed these multicomponent reactions to take place in good to excellent yields. The Mannich reaction, performed at room temperature, was also evaluated by means of electrospray (tandem) mass spectrometry - ESI-MS(/MS). ESI-MS data pointed to the origin of the ionic liquid effect, i.e., formation of ion pairs with the charged reaction intermediates and furthers association into larger supramolecular aggregates. DFT calculations revealed the strength of the supramolecular interactions between the charged species detected by ESI-MS and the spontaneity association of these ion pairs affording larger supramolecular aggregates.
- Alvim, Haline G.O.,Bataglion, Giovana A.,Ramos, Luciana M.,De Oliveira, Aline L.,De Oliveira, Heibbe C.B.,Eberlin, Marcos N.,De Macedo, Julio L.,Da Silva, Wender A.,Neto, Brenno A.D.
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p. 3306 - 3313
(2014/05/06)
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- Synthesis, anticonvulsant activity and molecular properties prediction of dialkyl 1-(di(ethoxycarbonyl)methyl)-2,6-dimethyl-4-substituted-1,4- dihydropyridine-3,5-dicarboxylates
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The synthesis and anticonvulsant properties of new N-diethylmalonyl derivatives of nifedipine and other isosteric analogues (7a-7n) were described. Anticonvulsant screening was performed by subcutaneous pentylenetetrazole (scPTZ) and maximal electroshock (MES) induced seizures tests. Majority of the compounds were effective in scPTZ and MES screens. Compound 7k showed good activity displaying maximum protection, which may be due to the presence of styryl moiety at position 4 of 1,4-dihydropyridine nucleus and the methyl groups of diester functionality. Compounds 7a-7d, 7g, 7i and 7k obeyed the Lipinski's "rule of five" and have drug-likeness. Based on computational prediction of molecular and pharmacokinetic properties, it was found that the compounds have good oral absorption.
- Prasanthi,Prasad,Bharathi
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- Metal-free-mediated oxidation aromatization of 1,4-dihydropyridines to pyridines using visible light and air
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A metal-free and environmentally friendly aerobic aromatization photosensitized by organic dye eosin Y bis(tetrabutyl ammonium salt) (TBA-eosinY) has been developed. With the aid of K2CO3, the aerobic catalytic system converts 1,4-dihydropyridines to their corresponding pyridine derivatives efficiently under visible light irradiation (λ=450 nm) at room temperature.
- Wei, Xiaojing,Wang, Lin,Jia, Wenliang,Du, Shaofu,Wu, Lizhu,Liu, Qiang
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supporting information
p. 1245 - 1250
(2015/02/05)
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- Triton-X-100 catalyzed synthesis of 1,4-dihydropyridines and their aromatization to pyridines and a new one pot synthesis of pyridines using visible light in aqueous media
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A realistic and convenient synthetic method has been developed for the facile synthesis of 1,4-dihydropyridine derivatives in the presence of the non-ionic surfactant Triton X-100, in an aqueous medium at room temperature. A greener method to synthesize pyridine derivatives has also been developed by the oxidation of 1,4-dihydropyridine derivatives with almost 100% yields and also in a one pot synthesis, employing an aldehyde, ethyl acetoacetate and ammonium acetate in an aqueous micellar medium by irradiation with potassium persulphate in the presence of visible light. The one pot protocol offered excellent yields of the targeted product in a very short period of time at room temperature and the non-ionic surfactant catalyst can be recovered very easily. We also observed that during the reaction there was the formation of micelles, or micelle-like colloidal aggregates, from the non-ionic surfactant and the reaction mixture in water, measured by dynamic light scattering and visualized through an optical microscope. The process is advantageous as ammonia is generated from an ammonium salt under absolutely neutral conditions and the product purification follows a group assistant purification chemistry process (GAP).
- Ghosh, Partha Pratim,Mukherjee, Prasun,Das, Asish R.
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p. 8220 - 8226
(2013/09/02)
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- Hantzsch 1,4-dihydropyridine synthesis in aqueous ethanol by visible light
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A highly efficient environment-friendly Hantzsch 1,4-dihydropyridine synthesis under visible light in aqueous ethanol has been achieved in excellent yield via a one-pot three component reaction of various types of aliphatic and aromatic aldehydes with ethyl acetoacetate and ammonium hydroxide solution.
- Ghosh, Somnath,Saikh, Forid,Das, Jhantu,Pramanik, Arun Kumar
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supporting information
p. 58 - 62
(2013/02/21)
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- Synthesis and characterization of redox-active charge-transfer complexes with 2,3,5,6-tetracyanopyridine (TCNPy) for the photogeneration of pyridinium radicals
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The heteroaromatic polynitrile compound tetracyanopyridine (TCNPy) is introduced as a new electron acceptor for the formation of deeply colored charge-transfer complexes. In MeCN, TCNPy is characterized by a quasireversible one-electron-reduction process at -0.51 V (versus SCE). The tetracyanopyridine radical anion undergoes a secondary chemical reaction, which is assigned to a protonation step. TCNPy has been demonstrated to generate 1:1 complexes with various electron donors, including tetrathiafulvalene (TTF) and dihydroxybenzene derivatives, such as p-hydroquinone and catechol. Visible- or NIR-light-induced excitation of the intense charge-transfer bands of these compounds leads to a direct optical electron-transfer process for the formation of the corresponding radical-ion pairs. The presence of available electron donors that contain protic groups in close proximity to the TCNPy acceptor site opens up a new strategy for the photocontrolled generation of pyridinium radicals in a stepwise proton-coupled electron-transfer (PCET) sequence. Copyright
- Woess, Eva,Monkowius, Uwe,Knoer, Guenther
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p. 1489 - 1495
(2013/03/14)
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- PAA-supported Hantzsch 1,4-dihydropyridine ester: An efficient catalyst for the hydrogenation of α,β-epoxy ketones
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A new type of water-soluble polymer-supported NADH co-enzyme model-PAA (polyacrylic acid)-supported Hantzsch 1,4-dihydropyridine ester (PAA-HEH) was designed and synthesized. Catalytic amount of the supported reagent was used in the hydrogenation of α,β-epoxy ketones to the corresponding β-hydroxy ketones and showed great catalytic efficiency in the reduction reaction. This PAA-HEH was an optimal potential for recycling use.
- Zhou, Xin-Feng,Wang, Peng-Fei,Geng, Ye,Xu, Hua-Jian
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supporting information
p. 5374 - 5377
(2013/09/12)
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- Design, solvent free synthesis, and antimicrobial evaluation of 1,4 dihydropyridines
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Here in, we report the usage of cellulose sulfuric acid as a heterogeneous eco friendly catalyst for the synthesis of 1,4 dihydropyridines under solvent free conditions via Hantzsch three component reaction of an aldehyde, ethyl acetoacetate and ammonium acetate at 100 °C for 2-5 h. In silico studies were performed on twenty two possible 1,4 dihydropyridines (DHPs) analogues against K+ channel receptor (KcsA). In order to validate in silico studies, thirteen compounds were synthesized and evaluated as antibacterials against twenty seven ESBL isolates of Klebsiella pneumoniae and Escherichia coli.
- Murthy,Rajack, Abdul,Taraka Ramji,Jeson Babu,Praveen, Ch.,Aruna Lakshmi
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p. 6016 - 6023
(2012/11/07)
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- Aerobic organocatalytic oxidation of aryl aldehydes: Flavin catalyst turnover by Hantzsch's ester
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The first Dakin oxidation fueled by molecular oxygen as the terminal oxidant is reported. Flavin and NAD(P)H coenzymes, from natural enzymatic redox systems, inspired the use of flavin organocatalysts and a Hantzsch ester to perform transition-metal-free, aerobic oxidations. Catechols and electron-rich phenols are achieved with as low as a 0.1 mol % catalyst loading, 1 equiv of Hantzsch ester, and O2 or air as the stoichiometric oxidant source.
- Chen, Shuai,Foss, Frank W.
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supporting information
p. 5150 - 5153,4
(2020/09/15)
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