- Understanding Ni(II)-Mediated C(sp3)-H Activation: Tertiary Ureas as Model Substrates
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We report a mechanistic study of C(sp3)-H bond activation mediated by nickel. Cyclometalated Ni(II) ureate [(PEt3)Ni(?3-C,N,N-(CH2)N(Cy)(CO)N((N)-quinolin-8-yl))] was synthesized and isolated from the urea precu
- Beattie, D. Dawson,Grunwald, Anna C.,Perse, Thibaut,Schafer, Laurel L.,Love, Jennifer A.
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Read Online
- The reactions of organoboranes with N-chloro-N-sodiocarbamates: A novel synthesis of N-alkylcarbamates
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Trialkylboranes react with N-chloro-N-sodiocarbamates to form N-alkylcarbamates in yields ranging from 50-88%. The reaction is best carried out without intermediate isolation of the N-chlorocarbamate salt. Only one of the alkyl groups of the trialkylborane is utilized.
- Wachter-Jurcsak,Scully Jr.
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Read Online
- Halogen-free process for the conversion of carbon dioxide to urethanes by homogeneous catalysis
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Carbon dioxide is converted to urethanes (carbamic acid derivatives) through reaction with amine and alcohol catalyzed by tin complexes; the addition of acetals as a dehydrating agent under high CO2 pressure is the key to achieve high yields.
- Abla,Choi,Sakakura
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Read Online
- A simple method for the synthesis of carbamates
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A new method for carbamate synthesis using aryl and alkylamines with sodium hydride and diethylcarbonate in dry benzene is described.
- Angeles,Santillan,Martinez,Ramirez,Moreno,Salmon,Martinez
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Read Online
- Activation of carbon dioxide by bicyclic amidines
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Activation of the carbon dioxide molecule was achieved using bicyclic amidines (DBU, PMDBD, and DBN). The solution reaction of CO2 with amidines yielded the corresponding zwitterionic complexes through the formation of a N-CO2 bond. 13C NMR data confirmed the carbamic nature of the carbamic zwitterions, DBU-CO2 and PMDBD-CO2. However, when these adducts were crystallized, the X-ray analyses of the single crystals were in agreement with bisamidinium bicarbonate salt structures, indicating that structural changes occurred in the crystallization process. The elemental and thermogravimetric analysis data for the carbamic zwitterions, DBU-CO2 and PMDBD-CO2, initially obtained by the direct reaction of amidines with CO2, suggest that these molecules are probably associated with one molecule of water by hydrogen-bond formation (amidinium+-COO-...H2O). A correlation was observed between the thermal stability and the transcarboxylating activity for the amidine-CO2 complexes. Theoretical calculations of hardness were performed at the B3LYP/cc-pVTZ level of theory and showed concordance with the experimental reactivity of DBU and PMDBD toward CO2.
- Perez, Eduardo R.,Santos, Regina H. A.,Gambardella, Maria T. P.,De Macedo, Luiz G. M.,Rodrigues-Filho, Ubirajara P.,Launay, Jean-Claude,Franco, Douglas W.
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Read Online
- Urethanes synthesis from oxamic acids under electrochemical conditions
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Urethane synthesis via oxidative decarboxylation of oxamic acids under mild electrochemical conditions is reported. This simple phosgene-free route to urethanes involves an in situ generation of isocyanates by anodic oxidation of oxamic acids in an alcoholic medium. The reaction is applicable to a wide range of oxamic acids, including chiral ones, and alcohols furnishing the desired urethanes in a one-pot process without the use of a chemical oxidant.
- Ogbu, Ikechukwu Martin,Lusseau, Jonathan,Kurtay, Gülbin,Robert, Frédéric,Landais, Yannick
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p. 12226 - 12229
(2020/10/26)
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- Chemoselective synthesis of carbamates using CO2 as carbon source
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Synthesis of carbamates directly from amines using CO2 as the carbon source is a straightforward and sustainable approach. Herein, we describe a highly effective and chemoselective methodology for the synthesis of carbamates at room temperature and atmosp
- Riemer, Daniel,Hirapara, Pradipbhai,Das, Shoubhik
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p. 1916 - 1920
(2018/08/17)
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- N-Substituted carbamate synthesis using urea as carbonyl source over TiO2-Cr2O3/SiO2 catalyst
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The use of urea as an active form of carbon dioxide is a feasible way to substitute phosgene in the chemical industry. This paper reports an effective route for the synthesis of N-substituted carbamates from amines, urea and alcohols. Under the optimized reaction conditions, several important N-substituted carbamates were successfully synthesized in 95-98% yields over a TiO2-Cr2O3/SiO2 catalyst. The catalyst could be reused for several runs without deactivation. The catalysts were characterized by BET, XPS, XRD, and TPD, which suggested that the strength and amount of the acidic and basic sites might be the major reason for the high catalytic activity of TiO2-Cr2O3/SiO2.
- Wang, Peixue,Ma, Yubo,Liu, Shimin,Zhou, Feng,Yang, Benqun,Deng, Youquan
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p. 3964 - 3971
(2015/07/15)
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- Direct reductive amination using triethylsilane and catalytic bismuth(III) chloride
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Direct reductive amination (DRA) using triethylsilane (TESH) and catalytic bismuth(III) chloride (BiCl3) is described for the first time. The use of TESH and BiCl3 provides easy handling, low cost, non-toxicity, and a mild Lewis acid activity, thereby meeting the demand for green and sustainable chemistry. The developed DRA is highly chemoselective and applicable to less-basic amines. The experimental results of this study revealed that the developed DRA could be catalyzed by BiCl3, which was gradually reduced to Bi(0) or bismuth with a low valency by TESH, but TESCl, Bi(0), and Bi(0) with TESCl catalyzed the DRA to some extent.
- Matsumura, Takehiko,Nakada, Masahisa
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p. 1829 - 1834
(2014/03/21)
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- Stereoselective direct reductive amination of ketones with electron-deficient amines using Re2O7/NaPF6 catalyst
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The first example of direct reductive amination (DRA) of ketones with electron-deficient amines (EDA) such as Cbz-, Boc-, EtOCO-, Fmoc-, Bz-, ArSO2-, etc. protected amines have been achieved using catalytic Re2O7/NaPF6. Excellent chemoselectivities as well as diastereoselectivity (for 2-alkyl cyclohexanones) were obtained. The Royal Society of Chemistry 2013.
- Das, Braja Gopal,Ghorai, Prasanta
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supporting information
p. 4379 - 4382
(2013/08/23)
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- Solvent free, N,N'-carbonyldiimidazole (CDI) mediated amidation
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The method involves CDI mediated amidation under solvent-free conditions. The protocol is green, simple, and scalable and has broad structural applicability. The protocol has also been used for BOC protection of amine. The protocol has reduced the time for CDI mediated amidation from 2-4 h to 5-10 min without the use of any dry organic solvent and nitrogen atmosphere.
- Verma, Sanjeev K.,Ghorpade, Ramarao,Pratap, Ajay,Kaushik
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experimental part
p. 2373 - 2376
(2012/05/31)
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- Green and practical synthesis of carbamates from ureas and organic carbonates
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A practical method for the synthesis of carbamates from ureas and organic carbonates was developed with 100% atom economy using La2O 3/SiO2 as catalyst without any additional solvent. The scope of the protocol is demonstrated in the synthesis of 14 carbamates with various functional groups in excellent yields (76-95%).
- Guo, Xiaoguang,Shang, Jianpeng,Li, Jian,Wang, Liguo,Ma, Yubo,Shi, Feng,Deng, Youquan
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experimental part
p. 1102 - 1111
(2011/05/02)
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- METHOD FOR PREPARING A CARBAMATE, A CATALYST APPLIED IN THE METHOD, A METHOD FOR PREPARING THE CATALYST AND USE THEREOF
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The present invention pertains to a novel method for preparing a carbamate, in which the method comprises reacting an aliphatic substituted urea and/or its derivatives, with a hydroxyl group containing compound to obtain a carbamate. In addition, the pres
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Page/Page column 6
(2010/12/26)
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- Carbamate synthesis from amines and dialkyl carbonate over inexpensive and clean acidic catalyst-Sulfamic acid
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Sulfamic acid has been proved to be the most efficient and recyclable catalyst in carbamate synthesis from alkylamine and dialkyl carbonate. High selectivity, cost-efficiency and simple product separation were the advantageous features obtained in this process. Sulfamic acid could be reused several times and keep its initial activity in the recycle runs. In addition, sulfamic acid has also exhibited the potential catalytic ability for alkylation of aromatic amines.
- Wang, Bo,He, Jing,Sun, Run Cang
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scheme or table
p. 794 - 797
(2011/11/13)
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- Study of the carbon dioxide chemical fixation-activation by guanidines
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Fixation of CO2 is one of the most important priorities of the scientific community dedicated to reduce global warming. In this work, we propose new methods for the fixation of CO2 using the guanidine bases tetramethylguanidine (TMG) and 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]-pyrimidine (TBD). In order to understand the reactions occurring during the CO2 fixation and release processes, we employed several experimental methods, including solution and solid-state NMR, FTIR, and coupled TGA-FTIR. Quantum mechanical NMR calculations were also carried out. Based on the results obtained, we concluded that CO2 fixation with both TMG and TBD guanidines is a kinetically reversible process, and the corresponding fixation products have proved to be useful as transcarboxylating compounds. Afterward, CO2 thermal releasing from this fixation product with TBD was found to be an interesting process for CO2 capture and isolation purposes.
- Pereira, Fernanda Stuani,deAzevedo, Eduardo Ribeiro,da Silva, Eirik F.,Bonagamba, Tito José,da Silva Agostíni, Deuber L.,Magalh?es, Alviclér,Job, Aldo Eloizo,Pérez González, Eduardo R.
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p. 10097 - 10106
(2008/12/22)
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- N-tosyloxycarbamates as reagents in rhodium-catalyzed C-H amination reactions
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Metal nitrenes for use in C-H insertion reactions were obtained from N-tosyloxycarbamates in the presence of an inorganic base and a rhodium(II) dimer complex catalyst. The C-H amination reaction proceeds smoothly, and the potassium tosylate that forms as a byproduct is easily removed by filtration or an aqueous workup. This new methodology allows the amination of ethereal, benzylic, tertiary, secondary, and even primary C-H bonds. The intramolecular reaction provides an interesting route to various substituted oxazolidinones, whereas the intermolecular reaction gives trichloroethoxycarbonyl-protected amines that can be isolated with moderate to excellent yields and that cleave easily to produce the corresponding free amine. The development, scope, and limitations of the reactions are discussed herein. Isotopic effects and the electronic nature of the transition state are used to discuss the mechanism of the reaction.
- Huard, Kim,Lebel, Helene
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scheme or table
p. 6222 - 6230
(2009/05/27)
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- De novo synthesis of troc-protected amines: Intermolecular rhodium-catalyzed C-H amination with N-tosyloxycarbamates
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The rhodium-catalyzed intermolecular C-H insertion of the nitrene derived from 2,2,2-trichloroethyl-N-tosyloxycarbamate proceeded in good to excellent yields to produce a variety of Troc-protected amines. With cyclic aliphatic alkanes, it is possible to use only 2 equiv of substrate, whereas the reaction with aromatic alkanes is run neat. Not only does the nitrene insertion proceed in benzylic, secondary, and tertiary C-H bonds but also primary C-H insertion products were obtained in good yields. Finally, the use of chiral rhodium catalysts to provide an enantioselective version of this process is discussed.
- Lebel, Helene,Kim, Huard
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p. 639 - 642
(2008/02/03)
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- Electrochemically promoted C-N bond formation from amines and CO 2 in ionic liquid BMIm-BF4: Synthesis of carbamates
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A new electrochemical procedure for the synthesis of organic carbamates from amines and carbon dioxide has been developed using selective cathodic reduction of carbon dioxide in CO2-saturated room-temperature ionic liquid BMIm-BF4 solutions containing amines 1a-j, followed by addition of EtI as an alkylating agent. The synthesis was carried out under mild (PCO2 = 1.0 atm, t = 55 °C) and safe conditions, and the use of volatile and toxic solvents and catalysts (according to the growing demand for ecofriendly synthetic methodologies), as well as of any supporting electrolyte (for a very easy workup of the reaction mixture), was avoided. Carbamates 2a-j were isolated in good to high yields.
- Feroci,Orsini,Rossi,Sotgiu,Inesi
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p. 200 - 203
(2007/10/03)
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- Mechanism of formation of organic carbonates from aliphatic alcohols and carbon dioxide under mild conditions promoted by carbodiimides. DFT calculation and experimental study
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Dicyclohexylcarbodiimide (CyN=C=NCy, DCC) promotes the facile formation of organic carbonates from aliphatic alcohols and carbon dioxide at temperatures as low as 310 K and moderate pressure of CO2 (from 0.1 MPa) with an acceptable rate. The conversion yield of DCC is quantitative, and the reaction has a very high selectivity toward carbonates at 330 K; increasing the temperature increases the conversion rate, but lowers the selectivity. A detailed study has allowed us to isolate or identify the intermediates formed in the reaction of an alcohol with DCC in the presence or absence of carbon dioxide. The first step is the addition of alcohol to the cumulene (a known reaction) with formation of an O-alkyl isourea [RHNC(ORO=NR] that may interact with a second alcohol molecule via H-bond (a reaction never described thus far). Such an adduct can be detected by NMR. In alcohol, in absence of CO 2, it converts into a carbamate and a secondary amine, while in the presence of CO2, the dialkyl carbonate, (RO)2CO, is formed together with urea [CyHN-CO-NHCy]. The reaction has been tested with various aliphatic alcohols such as methanol, ethanol, and allyl alcohol. It results in being a convenient route to the synthesis of diallyl carbonate, in particular. O-Methyl-N,N′-dicyclohexyl isourea also reacts with phenol in the presence of CO2 to directly afford for the very first time a mixed aliphatic-aromatic carbonate, (MeO)(PhO)CO. A DFT study has allowed us to estimate the energy of each intermediate and the relevant kinetic barriers in the described reactions, providing reasonable mechanistic details. Calculated data match very well the experimental results. The driving force of the reaction is the conversion of carbodiimide into the relevant urea, which is some 35 kcal/mol downhill with respect to the parent compound. The best operative conditions have been defined for achieving a quantitative yield of carbonate from carbodiimide. The role of temperature, pressure, and catalysts (Lewis acids and bases) has been established. As the urea can be reconverted into DCC, the reaction described in this article may further be developed for application to the synthesis of organic carbonates under selective and mild conditions.
- Aresta, Michele,Dibenedetto, Angela,Fracchiolla, Elisabetta,Giannoccaro, Potenzo,Pastore, Carlo,Papai, Imre,Schubert, Gabor
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p. 6177 - 6186
(2007/10/03)
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- Synthesis of Carbamates Using Yttria-Zirconia Based Lewis Acid Catalyst
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A variety of amines react with chloroformates in the presence of catalytic amount of yttria-zirconia based catalyst to afford the corresponding carbamates in excellent yields.
- Pandey, Rajesh K.,Dagade, Sharda P.,Dongare, Mohan K.,Kumar, Pradeep
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p. 4019 - 4027
(2007/10/03)
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- Cyanomethyl anion/carbon dioxide system: An electrogenerated carboxylating reagent. Synthesis of carbamates under mild and safe conditions
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A new carboxylating reagent (-CH2CN/CO2) was obtained by bubbling CO2 in a CH3CN-TEAP (tetraethylammonium perchlorate) solution previously electrolyzed under galvanostatic control. Organic carbamates were isolated from these solutions after addition of amines and an alkylating agent. In this paper, we describe the optimized conditions for the electrochemical synthesis of carbamates from amines and CO2, in mild and safe conditions, without any addition of bases, probases, or catalysts. Carbamates were isolated from primary and secondary aliphatic amines in high to excellent yields and from aromatic amines in moderate yields (dependent on the nucleophilicity of the nitrogen atom).
- Feroci, Marta,Casadei, Maria Antonietta,Orsini, Monica,Palombi, Laura,Inesi, Achille
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p. 1548 - 1551
(2007/10/03)
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- Efficient and clean synthesis of N-alkyl carbamates by transcarboxylation and O-alkylation coupled reactions using a DBU-CO2 zwitterionic carbamic complex in aprotic polar media
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N-Alkyl carbamates were obtained with good to excellent yields by clean and mild transcarboxylation of several amines with the previously synthesized DBU-CO2 complex and subsequent O-alkylation. Transcarboxylation was found to be selective, as
- Pérez, Eduardo R,Da Silva, Michele Odnicki,Costa, Vanessa C,Rodrigues-Filho, Ubirajara P,Franco, Douglas W
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p. 4091 - 4093
(2007/10/03)
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- A novel PdCl2/ZrO2-SO42- catalyst for synthesis of carbamates by oxidative carbonylation of amines
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At 170°C and ca. 4.0 MPa, oxidative carbonylation of aromatic amines to synthesize corresponding carbamates over a novel PdCl2/ZrO2-SO42- catalyst could proceed with high conversion and selectivity.
- Shi, Feng,Deng, Youquan,SiMa, Tianlong,Yang, Hongzhou
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p. 525 - 528
(2007/10/03)
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- The reaction of amines with an electrogenerated base. Improved synthesis of arylcarbamic esters
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The electrogenerated base of 2-pyrrolidone reacts with amines and anilines yielding the corresponding alkyl and aryl carbamates, after addition of carbon dioxide and ethyl iodide. Arylcarbamic esters are obtained in very good yields under mild reaction conditions with respect to the methods so far reported. (C) 2000 Elsevier Science Ltd.
- Feroci, Marta,Inesi, Achille,Rossi, Leucio
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p. 963 - 966
(2007/10/03)
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- Electrogenerated Superoxide-Activated Carbon Dioxide. A New Mild and Safe Approach to Organic Carbamates
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The electrochemical reduction of O2 (E = -1.0 V vs SCE) in dipolar aprotic solvents in the presence of CO2 gave a carboxylating reagent (O2·-/CO2) able to convert amines and different types of their derivatives into carbamates. Primary and secondary aliphatic and aromatic amines were converted into the corresponding ethyl carbamates by the addition of EtI to the carbamate anions generated in the first step of the reactions. The yields were dependent on the nucleophilicity of the nitrogen atom ω-Bromoethyl- and propylamine gave 2-oxazolidinone and tetrahydro-l,3-oxazm-2-one in moderate yields. N-Acyl or N-(alkoxycarbonyl)alkylamines bearing a leaving group at the β position of the alkyl substituent were converted into 3-substituted-2-oxazolidinones in high yields. By using chiral substrates, enantiopure 3-alkoxycarbonyl(or acyl)-4-substituted oxazolidin-2-ones (70-85% isolated yields) were obtained. This represents a new mild and safe route to these important auxiliaries for asymmetric synthesis. Some limitations of the process are also evidenced and accounted for.
- Casadei, Maria Antonietta,Moracci, Franco Micheletti,Zappia, Giovanni,Inesi, Achille,Rossi, Leucio
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p. 6754 - 6759
(2007/10/03)
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- Electrochemical activation of carbon dioxide: Synthesis of carbamates
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Electrochemically activated CO2 reacts with amines and EtI under mild reaction conditions affording the corresponding carbamates in high to excellent yields.
- Casadei, Maria A.,Inesi, Achille,Moracci, Franco Micheletti,Rossi, Leucio
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p. 2575 - 2576
(2007/10/03)
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- Reactivity of Carbamoyl Radicals. A New, General, Convenient Free-Radical Synthesis of Isocyanates from Monoamides of Oxalic Acid
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A new, general, simple synthesis of isocyanates was developed by oxidation of monoamides of oxalix acid with peroxydisulfate catalyzed by Ag and Cu salts.The reaction was carried out in a two-phase system (water and an organic solvent), and it is suitable also for practical applications, due to the simple experimental conditions and the inexpensive as well as nontoxic reagents.The first example of homolytic intramolecular aromatic carbamoylation is also reported.
- Minisci, Francesco,Fontana, Francesca,Coppa, Fausta,Yan, Yong Ming
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p. 5430 - 5433
(2007/10/02)
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- Method for treating swine dysentery with the derivatives of the antibiotic A82810
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New polyether antibiotic A82810, its acyl and alkyl ester, acyl ester and urethane derivatives, and salts thereof, are useful antibacterial and anticoccidial agents and increase feed-utilization efficiency in animals. Methods of making A82810 by culture of Actinomodura fibrosa sp. nov. NRRL 18348 and synergistic compositions of the A82810 compounds with nicarbazin, 4,4'-dinitrocarbanilide, certain napthalenamine and benzenamine compounds and metichlorpindol are also provided.
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- Processes for producing carbamates and isocyanates
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Processes for producing carbamates comprise contacting a first reactant selected from primary amine components, secondary amine components, urea components and mixtures thereof; carbon monoxide; at least one organic hydroxyl component and at least one oxygen-containing oxidizing agent in the presence of a catalyst composition comprising at least one metal macrocyclic complex, preferably in the further presence of a halogen component.
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- Oxidative Carbonylation of Amines Catalysed by Metallomacrocyclic Compounds
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Metallomacrocyclic compounds, such as metalloporphyrins, have been shown to catalyse the oxidative carbonylation of amines to carbamates which are precursors to isocyanates.
- Leung, Tak W.,Dombek, B. Duane
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p. 205 - 206
(2007/10/02)
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- Chemical Ionization Mass Spectra of Urethanes
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Chemical ionization mass spectra using methane as the reagent gas are reported for 33 urethanes of general structure RNHCO2C2H5 nH2n+1 (n=1-8), CH2CH=CH2, cyclo-C6H11, Ph, PhCH2, PhCH2CH2, and Ph(CH3)CH> and R2NCO2C2H5 nH2n+1 (n=1-4)>.Abundant MH+ ions are present in all the spectra, accompanied by satellite peaks corresponding to + and +.Four classes of fragment ions are of general importance in the spectra.Two of these, + and +, are associated with the CO2C2H5 group.The other two, corresponding to alkane and alkene elimination from MH+, arise from the RNH or R2N function.The mechanisms whereby these fragment ions are formed are discussed and their analytical utility is illustrated by reference to the spectra of the four isomeric C4H9NHCO2C2H5 and the eight isomeric C5H11NHCO2C2H5 compounds.The results of 2H-labelling studies are presented and a comparison is made between the methane and ammonia chemical ionisation spectra of selected urethanes.
- Wright, Andrew D.,Bowen, Richard D.,Jennings, Keith R.
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p. 1521 - 1528
(2007/10/02)
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- Photoinduced Nitrene, Carbene, and Atomic Oxygen Transfer Reactions Starting from the Corresponding Pyridinium N-, C-, and O-Ylides
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Ultraviolet irradiation of the pyridinium ylides 1, 2, and 3 led to fragmentation of the exocyclic polar bonds, as well as to skeletal rearrangements.The photoinduced fragmentation processes gave the corresponding pyridines and highly reactive intermediates, i. e. ethoxycarbonylnitrene, dicyanocarbene and atomic oxygen (oxene), respectively.Trapping of the reactive intermediates by alkanes and alkenes permitted the determination of their spin multiplicity.Ethoxycarbonylnitrene was in its triplet ground state at the moment of its formation.Dicyanocarbene occurred as a mixture of singlet and triplet, as determined by dilution experiments with variable amounts of alkenes.As to atomic oxygen, all collected data point to its formation in solution in its triplet ground state.
- Strub, Henri,Strehler, Christiane,Streith, Jacques
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p. 355 - 364
(2007/10/02)
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- Production of urethane compounds
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A process for producing a urethane compound which comprises reacting at least one compound selected from the group consisting of a primary amine, a secondary amine and a urea compound with carbon monoxide and an organic hydroxyl compound in the presence of a catalyst system comprising: (a) at least one member selected from the group consisting of platinum group metals and compounds containing at least one platinum group element; and (b) at least one halogen-containing compound selected from the group consisting of alkali or alkaline earth metal halides, onium halides, compounds capable of forming onium halides in the reaction, oxo acids of halogen atoms and their salts, complex compounds containing halogen ions, organic halides and halogen molecules, in the presence of molecular oxygen and/or an organic nitro compound as an oxidizing agent at a temperature of from about 80° C. to about 300° C. under a pressure of from about 1 Kg/cm2 to about 500 Kg/cm2.
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- Antibiotic A80190, pharmaceutical compositions containing same and method of use
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New polyether antibiotic A80190, its acyl and alkyl ester, acyl ester and urethane derivatives, and salts thereof, are useful antibacterial and anticoccidial agents and increase feed-utilization efficiency in animals. Methods of making A80190 by culture of Actinomodura oligospora NRRL 15877 and synergistic compositions of the A80190 compounds with nicarbazin, 4,4'-dinitrocarbanilide, certain napthalenamine and benzenamine compounds and metichlorpindol are also provided.
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- Triphenodioxazine acid dyes
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Triphenodioxazine dyes which, in the free acid form, have the formula: STR1 wherein A is Cl or Br; Y is cyclopentylene, cyclohexylene or (CH2)x where x is 2, 3 or 4; and Z is NRCO2 R1 or STR2 wherein R is H, optionally substituted alkyl or optionally substituted aryl; R1 is optionally substituted alkyl, optionally substituted cycloalkyl or optionally substituted aryl; and R2 is --CH=CH--,--CH=CH--CH2 --,--(CH2)--2-4 or a 1,2-radical of a 5 or 6 membered carbocyclic compound; or, when Y is cyclopentylene or cyclohexylene, Z may also be H or alkyl, alkoxy, aryl, aryloxy, cycloalkyl, cycloalkoxy or amino, all of which may be optionally substituted.
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- Electrophilic Aromatic N-Substitution by Ethoxycarbonylnitrenium Ion generated from Ethyl Azidoformate in the Presence of Trifluoroacetic Acid
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Thermal reactions of ethyl azidoformate with aromatic compounds in the presence of trifluoroacetic acid (TFA) gave ethyl N-arylcarbamates.Toluene, nitrobenzene, or naphthalene was selectively attacked on the ortho- and para-positions, on the ortho- and meta-positions, or in the 1- and 2-positions, respectively.The yields were ca. twice as high as those for thermolysis ( a nitrene-azepine route) in the absence of TFA with the subsequent addition of TFA at room temperature.The positional selectivities for toluene and naphthalene were lower for the former thermolysis than for the latter.The reactivity of cyclohexane or toluene relative to benzene was greater in the latter thermolysis than the former.A Hammett plot with ρ - 1.7 was obtained for the formation of ethyl N-arylcarbamates in the former thermolysis in TFA-nitrobenzene (8:2 v/v); the value was more negative than that (-1.32) for the disappearance of substituted benzenes in the reaction with ethoxycarbonylnitrene.The results suggest that the thermolysis in the presence of TFA involves an electrophilic aromatic N-substitution by ethoxycarbonylnitrenium ion.
- Takeuchi, Hiroshi,Mastubara, Eiji
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p. 981 - 985
(2007/10/02)
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- The Action of Nitrenes on Halogenothiophenes; Formation of Thiophene S,N-Ylides
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When ethyl or phenyl azidoformate, or p-tolylsulphonyl azide are decomposed in warm tetrachlorothiophene, tetrachlorothiophene S,N-ylides are formed; 2,5-dichloro-, 2,5-dibromo-, and tetrabromo-thiophene on the other hand give products arising from attack at the α-position followed by rearrangement.
- Meth-Cohn, Otto,Vuuren, Gerda van
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p. 190 - 191
(2007/10/02)
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- A Novel Catalytic Synthesis of Carbamates by the Oxidative Alkoxycarbonylation of Amines in the Presence of Platinum Group Metal and Alkali Metal Halide or Onium Halide
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Carbamates are prepared in good yields from amines, alcohols, CO, and oxygen in the presence of a novel catalyst system comprising platinum group metal and iodide.
- Fukuoka, Shinsuke,Chono, Masazumi,Kohno, Masashi
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p. 1458 - 1460
(2007/10/02)
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- A Novel Catalytic Synthesis of Carbamates by Oxidative Alkoxycarbonylation of Amines in the Presence of Palladium and Iodide
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Palladium and iodide catalyse the oxidative carbonylation of amines by CO, O2, and alcohols to give carbamates in high yields.
- Fukuoka, Shinsuke,Chono, Masazumi,Kohno, Masashi
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p. 399 - 400
(2007/10/02)
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- Amidomercuriation: A General Addition of Amides and Related Compounds to Olefins
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The addition of different carboxamides and related compounds such as urethane or urea to olefins using mercury(II) nitrate followed by sodium borohydride reduction to give the corresponding N-substituted amides, urethanes, or ureas, respectively, is described.The monoalkylated ureas, through the same amidomercuriation-demercuriation procedure, yield symmetrical and unsymmetrical N,N'-disubstituted ureas.This amidomercuriation-demercuriation process provides a new, convenient, and general method for the Markovnikov amidation of carbon-carbon double bonds.
- Barluenga, Jose,Jimenez, Carmen,Najera, Carmen,Yus, Miguel
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p. 591 - 593
(2007/10/02)
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- Electrophilic Aromatic Substitution by Ethoxycarbonylnitrenium Ion. Reactions of Ethyl Azidoformate with Aromatics in the Presence of Trifluoroacetic Acid
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Electrophilic aromatic substitution by ethoxycarbonylnitrenium ion occurs in reactions of ethyl azidoformate with aromatics in the presence of trifluoroacetic acid, giving ethyl n-arylcarbamates.
- Takeuchi, Hiroshi,Koyama, Kikuhiko
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p. 226 - 228
(2007/10/02)
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- The Reaction of Isocyanides with Halogens or N-Halosuccinimides and Alcohols
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The reaction of aliphatic isocyanides with bromine or chlorine in primary alcohols, followed by hydrolysis, afforded the corresponding carbamates in moderate yields, together with various amounts of amines.Bromine was superior to chlorine as a halogen source for the formation of carbamates, unexpectedly, the addition of HgCl2 resulted in a decrease in the carbamate yield.When N-halosuccinimides were used in the place of halogens, an additional formation of the succinimide-incorporated product was observed to some extent.
- Yamada, Hideyo,Wada, Yasuo,Tanimoto, Shigeo,Okano, Masaya
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p. 2480 - 2483
(2007/10/02)
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- Investigation of Thermally Induced α-Deoxysilylation of Organosilylated Hydroxylamine Derivatives as a General Method for Nitrene Production
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A variety of organosilylated hydroxylamine derivatives have been synthesized and studied as possible nitrene generators by thermally induced α-deoxysilylation: GN(OR')SiR3 GN + R'OSiR3, where G = EtO2C, ArCO, ArSO2, Me, H, and Ph2PO.The methods used to assess nitrene formation include trapping product characterization, substitutent variation, kinetic activation parameter measurements, Hammett studies, and solvent effects.While the latter two types of precursors were only briefly investigated because of their marked resistance to fragmentation, the combined data for the remaining compounds are consistent with the intermediacy of a nitrene.The existence of alternative deoxysilylation pathways is discussed in some cases, and for comparison with the nitrogen systems reported herein, kinetic activation parameters for α-deoxysilylation about carbon and silicon have been determined.
- Chang, Young Hwan,Chiu, Fang-Ting,Zon, Gerald
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p. 342 - 354
(2007/10/02)
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