- Light-Activated Sensitive Probes for Amine Detection
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Our new, simple, and accurate colorimetric method is based on diarylethenes (DAEs) for the rapid detection of a wide range of primary and secondary amines. The probes consist of aldehyde- or ketone-substituted diarylethenes, which undergo an amine-induced decoloration reaction, selectively to give the ring-closed isomer. Thus, these probes can be activated at the desired moment by light irradiation, with a sensitivity that allows the detection of amines at concentrations as low as 10?6m in solution. In addition, the practical immobilization of DAEs on paper makes it possible to detect biogenic amines, such as cadaverine, in the gas phase above a threshold of 12 ppbv within 30 seconds.
- Valderrey, Virginia,Bonasera, Aurelio,Fredrich, Sebastian,Hecht, Stefan
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Read Online
- Conformation of secondary amides. A predictive algorithm that correlates DFT-calculated structures and experimental proton chemical shifts
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The magnetic deshielding caused by the amido group on CON-CHα protons of secondary amides can easily be correlated with DFT-based structures at the B3LYP/6-31G* level of theory via a novel algorithm that refines previous models, such as the classical McConnell equation. The shift is given by δ = a + 2.16 cos2(α - 35)/d, where α denotes the virtual dihedral angle resulting from linking the carbonyl and the α-carbons and d is the distance (A) between the shifted proton and the carbonyl oxygen. Notably, in this equation a is a parameter that can be optimized for different solvents, namely, CDCl3, DMSO-d6, and D2O. For the development of these correlations, the preferential conformation of amides is taken from the optimized structures in the gas phase obtained at the DFT level. The deshielding on anti and gauche protons in both rotamers of (Z)-acetamides and E/Z isomers of formamides has been evaluated. This methodology has proved to be highly reliable, allowing us to discard ab initio or DFT conformational arrangements when shifts calculated by the above-mentioned equation differ from the experimental values. Thus, the anti disposition between the CHα proton and the N-H bond appears to be the more stable conformation of simple amides. For amides bearing only one proton at Cα, a local syn minimum can equally be characterized. The rotational barriers around the CON-alkyl bond along with the pyramidalization of the amido group have also been reassessed. As the conformation is taken away from anti or local syn minima, the nonplanarity of the amido group appears to increase.
- Avalos, Martin,Babiano, Reyes,Barneto, Jose L.,Cintas, Pedro,Clemente, Fernando R.,Jimenez, Jose L.,Palacios, Juan C.
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Read Online
- Design, synthesis and in vitro evaluation of novel SARS-CoV-2 3CLpro covalent inhibitors
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Severe diseases such as the ongoing COVID-19 pandemic, as well as the previous SARS and MERS outbreaks, are the result of coronavirus infections and have demonstrated the urgent need for antiviral drugs to combat these deadly viruses. Due to its essential role in viral replication and function, 3CLpro (main coronaviruses cysteine-protease) has been identified as a promising target for the development of antiviral drugs. Previously reported SARS-CoV 3CLpro non-covalent inhibitors were used as a starting point for the development of covalent inhibitors of SARS-CoV-2 3CLpro. We report herein our efforts in the design and synthesis of submicromolar covalent inhibitors when the enzymatic activity of the viral protease was used as a screening platform.
- Stille, Julia K.,Tjutrins, Jevgenijs,Wang, Guanyu,Venegas, Felipe A.,Hennecker, Christopher,Rueda, Andrés M.,Sharon, Itai,Blaine, Nicole,Miron, Caitlin E.,Pinus, Sharon,Labarre, Anne,Plescia, Jessica,Burai Patrascu, Mihai,Zhang, Xiaocong,Wahba, Alexander S.,Vlaho, Danielle,Huot, Mitchell J.,Schmeing, T. Martin,Mittermaier, Anthony K.,Moitessier, Nicolas
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- Concentration-dependent circularly polarized luminescence of chiral cyclometalated platinum(II) complexes for electroluminescence
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Circularly polarized organic light-emitting diodes (CP-OLEDs) have been attracting increasing attention due to the direct generation of CP light, and they show the improved image contrast and luminous efficiency in OLEDs displays. In this work, a pair of chiral Pt(II) complexes with methylbenzylisocyanide and 1,3-bis(2-pyridyl)benzene as a tridentate N∧C∧N ligand were synthesized. Both of them exhibited bright green emission in dilute acetonitrile solution, while strong orange emission in high concentration of acetonitrile solution. However, when the complexes were doped into polymethyl methacrylate, the green emission originated from intrinsic single molecule can be changed to the red emission from excimer by adjusting the doping ratios. More importantly, the amplification of CPL signal can be achieved compared with the solution state. Furthermore, the monochrome devices were fabricated by utilizing these two enantiomers as emitters.
- Guo, Song,Han, Jianmei,Liu, Shujuan,Lu, Hu,Tao, Peng,Xu, Yanan,Zhang, Xinwen,Zhao, Qiang,Zheng, Xiaokang
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- Metal-free Carbon Monoxide (CO) Capture and Utilization: Formylation of Amines
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The capture and utilization of CO by 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) were performed in the absence of transition-metal complexes. The reaction of TBD with CO afforded TBD-CO adducts, which were converted to formylated TBD (TBD-CHO). TBD-CO adducts may include an interaction of CO with positively charged species based on NMR and IR analysis. In the presence of amines, CO was transferred from TBD-CO to amines, producing formylated amines with good yields. The reaction mechanism involving TBD-CO adducts is presented based on theoretical calculations. (Figure presented.).
- Noh, Hyeong-Wan,An, Youngjoon,Lee, Seulchan,Jung, Jaehoon,Son, Seung Uk,Jang, Hye-Young
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supporting information
(2019/04/26)
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- N-formylation of amine using graphene oxide as a sole recyclable metal-free carbocatalyst
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Abstract: Graphene oxide (GO), an inexpensive, environment-friendly, and metal-free carbocatalyst, used for the N-formylation of amines is developed. In this reaction, GO shows good activity, selectivity, and recyclability. This strategy has an array of advantages, such as being metal free, without additive, wide-scope protocol, scalable with a low catalyst loading of 3?wt%, use of readily available and recyclable carbocatalyst, and DMF as a readily available formyl source. Furthermore, this strategy provides an avenue for the convenient hydroformylation of various amines. Graphical abstract: [Figure not available: see fulltext.].
- Ma, Juan,Zhang, Jingyu,Zhou, Xiao,Wang, Jiawei,Gong, Hang
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p. 2851 - 2860
(2018/10/31)
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- Method for synthesizing formamide derivatives by molybdenum catalyzed formylation reaction
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The invention discloses a method for synthesizing formamide derivatives by molybdenum catalyzed formylation reaction. The method includes that the formamide derivatives are generated by one-pot reaction of amine compounds and formamide compounds under the catalytic action of molybdenum salts and/or molybdenum oxides. Reaction methods and catalysts are cheap and easy to acquire, reaction steps andoperations are simple, the method has advantages of high reaction selectivity, high yield, expandability in reaction and the like, and defects of high toxicity of reaction agents, expensive catalysts,complex reaction steps, high quality of by-products and the like in the prior art are overcome.
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Paragraph 0073; 0074
(2018/05/16)
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- First report on bio-catalytic N-formylation of amines using ethyl formate
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A bio-catalyzed N-formylation reaction of different amines has been developed using ethyl formate as a formylating agent. This protocol provides a facile and convenient strategy featuring mild reaction conditions, high efficacy, a broad substrate scope and recyclability of lipase. This method also works on a large scale in high yield.
- Patre, Rupesh E.,Mal, Sanjib,Nilkanth, Pankaj R.,Ghorai, Sujit K.,Deshpande, Sudhindra H.,El Qacemi, Myriem,Smejkal, Tomas,Pal, Sitaram,Manjunath, Bhanu N.
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supporting information
p. 2382 - 2385
(2017/02/23)
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- Nonacidic Farnesoid X Receptor Modulators
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As a cellular bile acid sensor, farnesoid X receptor (FXR) participates in regulation of bile acid, lipid and glucose homeostasis, and liver protection. Clinical results have validated FXR as therapeutic target in hepatic and metabolic diseases. To date, potent FXR agonists share a negatively ionizable function that might compromise their pharmacokinetic distribution and behavior. Here we report the development and characterization of a high-affinity FXR modulator not comprising an acidic residue.
- Flesch, Daniel,Cheung, Sun-Yee,Schmidt, Jurema,Gabler, Matthias,Heitel, Pascal,Kramer, Jan,Kaiser, Astrid,Hartmann, Markus,Lindner, Mara,Lüddens-D?mgen, Kerstin,Heering, Jan,Lamers, Christina,Lüddens, Hartmut,Wurglics, Mario,Proschak, Ewgenij,Schubert-Zsilavecz, Manfred,Merk, Daniel
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supporting information
p. 7199 - 7205
(2017/09/07)
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- Chemoselective Schwartz Reagent Mediated Reduction of Isocyanates to Formamides
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Addition of the in situ generated Schwartz reagent to widely available isocyanates constitutes a chemoselective, high-yielding, and versatile approach to the synthesis of variously functionalized formamides. Steric and electronic factors or the presence of sensitive functionalities (esters, nitro groups, nitriles, alkenes) do not compromise the potential of the method. Full preservation of the stereochemical information contained in the starting materials is observed. The use of formamides in the nucleophilic addition of organometallic reagents (Chida-Sato allylation, Charette-Huang addition to imidoyl triflate activated amides, Matteson homologation of boronic esters) is briefly investigated.
- Pace, Vittorio,De La Vega-Hernández, Karen,Urban, Ernst,Langer, Thierry
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supporting information
p. 2750 - 2753
(2016/06/15)
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- Transamidation catalysed by a magnetically separable Fe3O4 nano catalyst under solvent-free conditions
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An environmentally benign protocol for transamidation of carboxamides with different amines under solvent free conditions using magnetically separable nano Fe3O4 as a heterogeneous catalyst is developed. The series of aryl and alkyl amines with long chain alkyl substituents have been selectively converted into transamide products. The current protocol offers a diverse substrate scope with good yield of the product. The Fe3O4 nano catalyst has also been used for formylation of amines via transamidation of dimethyl formamide. Efficient transamidation, ease of work up, simple separation and reusability of the catalyst for up to six runs are the important highlights of this process.
- Thale, Pranila B.,Borase, Pravin N.,Shankarling, Ganapati S.
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p. 52724 - 52728
(2016/06/14)
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- Hydrogen acceptor- and base-free N-formylation of nitriles and amines using methanol as C1 source
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An N-formylation method using methanol as the C1 source without a stoichiometric amount of activating reagent is described. Nitriles as well as amines can be directly used as substrates. The reaction is catalyzed by an N-heterocyclic carbene coordinated ruthenium(II) dihydride complex, which mediates methanol dehydrogenation, nitrile reduction, and C-N bond formation without any external base, hydrogen acceptor, or oxidant.
- Kang, Byungjoon,Hong, Soon Hyeok
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supporting information
p. 834 - 840
(2015/03/18)
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- A Practical and General Base-Catalyzed Carbonylation of Amines for the Synthesis of N-Formamides
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A highly practical and general base-catalyzed carbonylation of amines to the corresponding N-formamides has been realized. Cheap inorganic bases, including GroupIA and IIA metal hydroxides, alkoxides, carbonates, and phosphates, were effective catalysts for the transformation. In the presence of 10-40mol% of KOH or K2CO3, various amines were converted into the corresponding N-formamides in good-to-excellent yields using CO as the formylation reagents. Metal-free carbonylation: A simple and practical procedure for the catalytic carbonylation of amines has been developed (see scheme). In the presence of 10-40mol% of KOH or K2CO3, various amines have been converted into the corresponding N-formamides in good-to-excellent yields by using CO as the formylation reagent.
- Li, Wanfang,Wu, Xiao-Feng
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supporting information
p. 14943 - 14948
(2015/10/19)
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- Enantioselective addition of diethylzinc to aldehydes catalyzed by (R)-1-phenylethylamine-derived 1,4-amino alcohols
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A series of o-xylylene-type 1,4-amino alcohols, synthesized from (R)-1-phenylethylamine, were used as chiral ligands for the enantioselective addition of diethylzinc to benzaldehyde. (S)-1-Phenyl-1-propanol was obtained with high enantioselectivity in all cases since the stereochemical outcome of the reaction was controlled by the chiral benzylic carbon bearing amino group. Highest catalytic activity was obtained by using (R)-1-{2-[1-(pyrrolidin-1-yl)ethyl]phenyl}cyclohexan-1-ol (1n) derived from (R)-1-(1-phenylethyl)pyrrolidine and cyclohexanone. Various chiral secondary alcohols were obtained by the reaction of diethylzinc and aldehydes in the presence of 1n within 2 h with good to high enantioselectivities.
- Asami, Masatoshi,Miyairi, Naomichi,Sasahara, Yukihiro,Ichikawa, Ken-Ichi,Hosoda, Naoya,Ito, Suguru
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p. 6796 - 6802
(2015/08/24)
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- Effective Formylation of Amines with Carbon Dioxide and Diphenylsilane Catalyzed by Chelating bis(tzNHC) Rhodium Complexes
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The reductive formylation of amines using CO2 and hydrosilanes is an attractive method for incorporating CO2 into valuable organic compounds. However, previous systems required either high catalyst loadings or high temperatures to achieve high efficiency, and the substrate scope was mostly limited to simple amines. To address these problems, a series of alkyl bridged chelating bis(NHC) rhodium complexes (NHC=N-heterocyclic carbene) have been synthesized and applied to the reductive formylation of amines using CO2 and Ph2SiH2. A rhodium-based bis(tzNHC) complex (tz=1,2,3-triazol-5-ylidene) was identified to be highly effective at a low catalyst loading and ambient temperature, and a wide substrate scope, including amines with reducible functional groups, were compatible. Beyond the norm: Rhodium complexes bearing a strong electron-donating bis(1,2,3-triazol-5-ylidene) ligand were found to be excellent catalysts for the reductive formylation of amines with CO2 and Ph2SiH2 at ambient temperature. The catalyst system possesses a broad substrate scope which tolerates a variety of reducible functional groups and is suitable for the synthesis of bioactive compounds. Tf=trifuoromethanesulfonyl.
- Nguyen, Thanh V. Q.,Yoo, Woo-Jin,Kobayashi
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supporting information
p. 9209 - 9212
(2015/08/06)
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- Direct synthesis of amides from carboxylic acids and amines using B(OCH2CF3)3
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B(OCH2CF3)3, prepared from readily available B2O3 and 2,2,2-trifluoroethanol, is as an effective reagent for the direct amidation of a variety of carboxylic acids with a broad range of amines. In most cases, the amide products can be purified by a simple filtration procedure using commercially available resins, with no need for aqueous workup or chromatography. The amidation of N-protected amino acids with both primary and secondary amines proceeds effectively, with very low levels of racemization. B(OCH2CF3)3 can also be used for the formylation of a range of amines in good to excellent yield, via transamidation of dimethylformamide.
- Lanigan, Rachel M.,Starkov, Pavel,Sheppard, Tom D.
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p. 4512 - 4523
(2013/06/05)
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- Chain branching approach in structure modification of TRPV1 receptor antagonist MK056 and its analogs
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A series of chain branched 1,3-dibenzylthiourea derivatives were designed, synthesized, and evaluated for their antagonist activity against TRPV1. The synthesized chain branched 1,3dibenzylthioureas 9a-g were tested for their antagonist activities against TRPV1 by 45 Ca 2+ influx assay using neonatal rat cultured spinal sensory neurons. Fluorinated ethyl-branched analog 9g showed the most potent antagonist activity with an IC50 value of 0.41 μM, but all of the chain branched analogs were less potent than the parent compounds MK-056 and SC0030, indicating that chain branching on the benzylic position of B-ring is detrimental to potency. Optimized receptor binding seems to be interfered by chain branching, and resulted in decrease in potency.
- Jang, Mijung,Ryu, Chong Hyun,Park, Young-Ho,Kim, Hee-Doo
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scheme or table
p. 321 - 326
(2012/08/29)
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- Sulfated tungstate catalyzed highly accelerated N-formylation
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Sulfated tungstate catalyzed, green, rapid, and practical method for N-formylation of amines using formic acid under solvent-free conditions is described. This method showed improvements over the reported in terms of yield, reaction time, and chemoselectivity.
- Pathare, Sagar P.,Sawant, Ravindra V.,Akamanchi, Krishnacharya G.
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experimental part
p. 3259 - 3263
(2012/07/30)
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- Chiral aminophosphines as catalysts for enantioselective double-michael indoline syntheses
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The bisphosphine-catalyzed double-Michael addition of dinucleophiles to electron-deficient acetylenes is an efficient process for the synthesis of many nitrogencontaining heterocycles. Because the resulting heterocycles contain at least one stereogenic center, this double-Michael reaction would be even more useful if an asymmetric variant of the reaction were to be developed. Aminophosphines can also facilitate the double-Michael reaction and chiral amines are more readily available in Nature and synthetically; therefore, in this study we prepared several new chiral aminophosphines. When employed in the asymmetric double-Michael reaction between ortho-tosylamidophenyl malonate and 3-butyn-2-one, the chiral aminophosphines produced indolines in excellent yields with moderate asymmetric induction.
- Khong, San N.,Kwon, Ohyun
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scheme or table
p. 5626 - 5650
(2012/07/03)
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- Self-disproportionation of enantiomers of non-racemic chiral amine derivatives through achiral chromatography
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Efficient self-disproportionation of enantiomers of several non-racemic chiral amines was achieved through conversion to N-acetamides and subsequent MPLC using an achiral column. The MPLC of these non-racemic N-acetamide derivatives gave the chart having a clear boundary between two fractions. Thus, in the less polar fraction, remarkable enantiomer enrichment was observed (>99%ee), while the ee of more polar fraction was considerably reduced. The magnitude of the enantiomer enrichments and depletions strongly depended on substituent on the amino group.
- Nakamura, Tsuyoshi,Tateishi, Kaori,Tsukagoshi, Shiori,Hashimoto, Saori,Watanabe, Shotaro,Soloshonok, Vadim A.,Ace?a, José Luis,Kitagawa, Osamu
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experimental part
p. 4013 - 4017
(2012/07/14)
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- Boric acid: A highly efficient catalyst for transamidation of carboxamides with amines
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A novel method of transamidation of carboxamides with amines using catalytic amounts of readily available boric acid under solvent-free conditions has been developed. The scope of the methodology has been demonstrated with (i) primary, secondary, and tertiary amides and phthalimide and (ii) aliphatic, aromatic, cyclic, acyclic, primary, and secondary amines.
- Nguyen, Thanh Binh,Sorres, Jonathan,Tran, Minh Quan,Ermolenko, Ludmila,Al-Mourabit, Ali
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supporting information; experimental part
p. 3202 - 3205
(2012/08/07)
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- N-Formylsaccharin: A new formylating agent
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N-Formylsaccharin, a very cheap reagent, has been revealed to be an efficient and chemoselective formylating agent of amines. Georg Thieme Verlag Stuttgart New York.
- Cochet, Thomas,Bellosta, Véronique,Greiner, Alfred,Roche, Didier,Cossy, Janine
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experimental part
p. 1920 - 1922
(2011/10/02)
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- Sulfonic acid supported on hydroxyapatite-encapsulated-γ-Fe2O3 nanocrystallites as a magnetically Br?nsted acid for N-formylation of amines
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Treatment of aqueous formic acid (85%) with structurally diverse amines in the presence of a catalytic amount of sulfonic acid supported on hydroxyapatite-encapsulated-γ-Fe2O3 [HAp@-γ-Fe2O3] (0.9 mol.%) as a heterogeneous, reusable and highly efficient catalyst gave the corresponding formamides in good to excellent yields at room temperature. The magnetically catalytic system was recovered by-passing time consuming filtration operation by using an external magnet device. In addition to facility, this methodology, it also enhances product purity and promises economic as well as environmental benefits.
- Ma'mani, Leila,Sheykhan, Mehdi,Heydari, Akbar,Faraji, Mohammad,Yamini, Yadollah
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experimental part
p. 64 - 69
(2010/07/05)
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- Iridium-catalyzed formylation of amines with paraformaldehyde
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Amines have been formylated using aqueous formaldehyde or paraformaldehyde and the iridium catalyst [CpIrI2]2. Paraformaldehyde acts as both a formylating agent and an oxidant.
- Saidi, Ourida,Bamford, Mark J.,Blacker, A. John,Lynch, James,Marsden, Stephen P.,Plucinski, Pawel,Watson, Robert J.,Williams, Jonathan M.J.
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body text
p. 5804 - 5806
(2010/11/05)
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- Silver-mediated direct amination of benzoxazoles: Tuning the amino group source from formamides to parent amines
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Formamides or parent amines were used as an amino group source for the silver-mediated amination of benzoxazoles. Although reactions with formamides proceeded at high temperatures, the direct amination with amines took place under much milder conditions (
- Cho, Seung Hwan,Kim, Ji Young,Lee, S. Yunmi,Chang, Sukbok
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supporting information; experimental part
p. 9127 - 9130
(2010/03/04)
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- Catalytic enantioselective addition of organometallic reagents to N-formylimines using monodentate phosphoramidite ligands
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(Chemical Equation Presented) The asymmetric synthesis of protected amines via the copper/phosphoramidite-catalyzed addition of organozinc and organoaluminum reagents to N-acylimines, generated in situ from aromatic and aliphatic α-amidosulfones, is reported. High yields of optically active N-formyl-protected amines and enantioselectivities up to 99% were obtained. Under the reaction conditions, partial oxidation of the phosphoramidite ligand to the corresponding phosphoric amide was detected. A preliminary study on the origin and the effect on the catalytic addition reaction is presented.
- Pizzuti, Maria Gabriella,Minnaard, Adriaan J.,Feringa, Ben L.
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p. 940 - 947
(2008/09/18)
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- Asymmetric control in Diels-Alder cycloadditions of chiral 9-aminoanthracenes by relay of stereochemical information
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Two approaches to the synthesis of chiral 9-amino anthracenes are described. The first, by nucleophilic addition of organolithium reagents to imines promoted by BF3·OEt2, unexpectedly provided stable aminoboranes as products. The second approach, using palladium catalysed cross coupling, was more successful for primary amines, and the key 9-(α-methylbenzylamino)anthracene subjected to cycloadditions with N-methyl maleimide and maleic anhydride. Excellent reactivity was achieved with good levels of diastereoselectivity, through a favourable combination of electrostatic and hydrogen bonding effects. Trial studies of the retro Diels-Alder reaction of these cycloadducts were also performed.
- Adams, Harry,Bawa, Ramadan A.,McMillan, Keith G.,Jones, Simon
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p. 1003 - 1012
(2008/02/03)
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- Synthesis of N-Methyl-N-{(1S)-1-[(3R)-pyrrolidin-3-yl]ethyl} amine
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N-Methyl-N-{(1S)-1-[(3R)-pyrrolidin-3-yl]ethyl} amine (1)1 is a key intermediate in the preparation of premafloxacin (2), which was under development as an antibiotic for use against pathogens of veterinary importance. This paper describes the development of a practical, efficient, and stereoselective process for the preparation of 1 from isobutyl (3S)-3-{methyl[(1S)-1-phenylethyl]-amino}butanoate (5c). The key steps in the synthetic sequence are an asymmetric Michael addition, which yields 5c, and a stereoselective alkylation, which yields (3S,4S)-3-allyl-1,4-dimethylazetidin-2-one (17).
- Fleck, Thomas J.,McWhorter Jr., William W.,DeKam, Richard N.,Pearlman, Bruce A.
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p. 9612 - 9617
(2007/10/03)
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- 2,2,2-trifluoroethyl formate: a versatile and selective reagent for the formylation of alcohols, amines, and N-hydroxylamines.
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[reaction: see text] Treatment of a variety of alcohols, amines, and N-hydroxylamines with 2,2,2-trifluoroethyl formate gave the corresponding formylated adducts in high yields.
- Hill, David R,Hsiao, Chi-Nung,Kurukulasuriya, Ravi,Wittenberger, Steven J
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p. 111 - 113
(2007/10/03)
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- Optically active 3-(1-(alkylamino))alkyl pyrrolidines
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This invention relates to processes for the synthesis of various optically active amino pyrrolidinyl stereoisomers, or enantiomers, that may be attached to quinolonecarboxylic acids or naphthyridones. Processes and essential intermediates are disclosed an
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- Asymmetric Catalysis, 77. - New Optically Active Pyrazole Derivatives for Enantioselective Catalysis
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Starting from the amines 3-6 and the dipyrazolopyrazinedione 2, the optically active (pyrazolylmethyl)amines 11-14 have been synthesized.Furthermore, the preparation of the (+)-camphor-derived optically active pyrazole 17 is described.Pyrazoles 11-13 and 17 are introduced as chiral building blocks into the 2-(1-pyrazolyl)pyridines 30-33.The optically active compounds 23-25 are formed from 2-pyridine and 2,6-bispyridine, respectively, and (+)-3-(bromomethyl)pinane.The pyrazole derivatives 27-29 contain (+)-(1-phenylethyl)hydrazine as the optically active component.Key Words: Pyrazoles, optically active / Pyridines, 2--, 2,6-bis-, 2-(1-pyrazolyl)-
- Brunner, Henri,Scheck, Thomas
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p. 701 - 710
(2007/10/02)
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- Stereoselective α-Methylation of N-Methyl Benzylamine via a Combination of Chromium Tricarbonyl and Chiral Formamidine Methodologies.
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Whereas carbanions of formamidines derived from N-methyl benzylamine and L-valinol or L-leucinol undergo electrophilic benzylic methylation with poor stereoselectivities (d.e. 17-26percent), enhanced stereoselectivities (d.e. 74-84percent) are observed for the corresponding chromium tricarbonyl complexes.
- Albert, Joan,Davies, Stephen G.
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p. 5945 - 5948
(2007/10/02)
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- N-Formylation of Aliphatic Primary Amines with N,N-Dimethylformamide Promoted by 2,3-Dihydro-1,4-naphthalazinedione
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The N-formylation of aliphatic primary amine proceeded very effectively in N,N-dimethylformamide in the presence of restorable 2,3-dihydro-1,4-naphthalazinedione.
- Iwata, Masaaki,Kuzuhara, Hiroyoshi
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p. 2029 - 2030
(2007/10/02)
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- ATROPISOMERISM IN POLYMERS. SCREW-SENSE SELECTIVE POLYMERIZATION OF ISOCYANIDES BY INHIBITING THE GROWTH OF ONE ENANTIOMER OF A RACEMIC PAIR OF HELICES.
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The authors describe a method for the preparation of a polymer with an excess of either left- or right-handed helices, starting from an achiral isocyanide. To this end, they added a slowly polymerizing optically active isocyanide as comonomer to a rapidly polymerizing achiral isocyanide. CD spectra and optical rotation indicate that the screw sense of the resulting polymer samples is opposite to the one preferred by the homopolymer of the optically active comonomer. A mechanism is proposed according to which the optically active comonomer is preferentially incorporated in one of the two helices formed from the achiral isocyanide, viz. the one that corresponds to its own homopolymer.
- Kamer,Cleij,Nolte,Harada,Hezemans,Drenth
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p. 1581 - 1587
(2007/10/02)
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- Base Catalysed Rearrangements involving Ylide Intermediates. Part 18. Competing , , and Rearrangements of Ammonium Ylides
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The rearrangements of acyl stabilised ammonium ylides are, in several cases, accompanied by competing rearrangements and in one case by a rearrangement.For examples involving migrating benzyl or phenylethyl groups the mechanism of these rearrangements has been studied.Thus the competing , , and rearrangements of the ylide (12) are largely intramolecular, but the intermolecularity is as high as 28percent for the and rearrangements and 14percent for the rearrangement in methanol at 55 deg C.The competing and rearrangements of the optically active (29a) give products with predominant retention of the configuration of the migrating phenylethyl group, but the intramolecular stereoselectivity of the rearrangement is significantly greater than that of the rearrangement.These results are consistent with a radical pair pathway for all three modes of rearrangement.Suitably substituted acyl stabilised allylammonium ylides (55) rearrange by competing , and processes.
- Chantrapromma, Kan,Ollis, W. David,Sutherland, Ian O.
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p. 1049 - 1062
(2007/10/02)
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- CATALYTIC ALKYL GROUP EXCHANGE REACTION OF PRIMARY AND SECONDARY AMINES.
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It has been shown that primary and secondary amines undergo alkyl group exchange reactions upon treatment with palladium catalyst as depicted in an operationally simple and efficient reaction which provides a convenient method for synthesis of unsymmetrical amines. The application of the reaction for the preparation of various substituted amines and heterocyclic compounds such as hexahydropyrimidine tetrahydropyrimidine, imidazolidine, and imidazoles is described. The preparation of polyamines such as H//2N(CH//2)//mNH(CH//2)//nNH//2 (10) and H//2N(CH//2)//lNH(CH//2)//mNH(CH//2)//nNH//2 (l-n, equals 2,3; 11) is readily performed by the appadium-catalyzed reactions of azetidine (6) and aziridine (7) via azetine (9) and azirine intermediates. The mechanism the palladium-catalyzed reaction has been extensively studied on the carbonylation, racemization, and deuteurium-exchange reaction of (S)-( minus )- alpha -phenylethylamine (17).
- Murahashi,Yoshimura,Tsumiyama,Kojima
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p. 5002 - 5011
(2007/10/02)
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- Derecemization par protonation enantioselective. Application a un α-aminoacide, la phenylglycine
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This work describes the application of deracemization by enantioselective protonation to α-aminoacid derivatives.Esters of phenylglycine are readly converted into Schiff bases.Melanation of the latter by a lithium amide, followed by protonation by a chiral acid, leads to the optically active starting materials (e.e. as high as 70percent).Chiral acids can easily be retrieved after protonation with excellent yields and conservation of enantiomeric purity.A mechanism responsible for the asymmetric induction is suggested by means of a study of the parameters modifying the selectivity, such as the nature of protecting groups, chiral acid, and lithium amide.
- Duhamel, Lucette,Plaquevent, Jean-Christophe
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- Helical configuration of poly(tert-butyliminomethylene). Complete resolution and maximum optical rotation
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By repeated chromatography over optically active poly(sec-butyliminomethylene) on glass beads complete resolution of poly(tert-butyliminomethylene) was obtained.The specific rotation increases with molecular weight up to 57820 = 56 +/- 2 deg at approxymately 20 repeating units.
- Beijnen, A. J. M. van,Nolte, R. J. M.,Drenth, W.
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p. 121 - 123
(2007/10/02)
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