- [2+2] and [2+4] type cycloadditions of isocyanates with ynolates
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Ynolates react with isocyanates to give azetidine-2,4-diones via a [2+2] type cycloaddition. The [4+2] type cycloaddition proceeds in the reactions of vinyl isocyanates with ynolates to provide 2-pyridones.
- Shindo, Mitsuru,Harada, Akiko,Matsumoto, Kenji,Shishido, Kozo
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- Preparation and applications of a polymer-supported phosphoryl azide
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A polymer-supported diphenylphosphoryl azide was prepared. This polymer-supported version of DPPA is useful due to its lower toxicity, moisture tolerance and ease of workup after reaction. The synthetic application of this solid-phase reagent was explored by conversion of a variety of carboxylic acids to urethanes and ureas through Curtius rearrangement reactions. Carboxylic acids bearing different functional groups (aromatic, aliphatic and heterocyclic carboxylic acids) were subjected to the reaction. The corresponding products were isolated with satisfactory yields.
- Lu, Yuhua,Taylor, Richard T.
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- Ultrasound promoted 'one pot' conversion of nitrocompounds to carbamates
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An efficient ultrasound promoted novel direct conversion of nitro compounds to N-(tert-butoxycarbonyl) amines and N-(ethoxycarbonylamines) is achieved using Sn-NH4Cl for the first time.
- Chandrasekhar,Narsihmulu,Jagadeshwar
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- Chemistry and antioxidant properties of titanium(IV) complexes
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Abstract The synthesis of titanium(IV) complexes with biologically active hydrazide ligands has been carried out. The complexes were characterized by spectroscopic methods (IR, 1H NMR and 13C NMR), elemental analysis and conductivity studies. These studies suggest bidentate coordination of the ligands through carbonyl oxygen and primary amine nitrogen, resulting in octahedral geometries. Hydrazides with pyridyl substituents displayed 1:2 metal-to-ligand ratio, and hydrazides with imino substituents exhibited 1:3 metal-to-ligand ratio resulting in an outer sphere complex. The remaining complexes displayed inner sphere coordination with 1:1 metal-to-ligand ratio. These complexes exhibit varying degrees of radical scavenging properties against DPPH, superoxide and nitric oxide free radicals. The free ligands showed inhibition against DPPH but were inactive against superoxide and nitric oxide free radicals. The structure-activity relationships of the complexes are discussed.
- Shaikh, Zara,Ashiq, Uzma,Jamal, Rifat Ara,Mahroof-Tahir, Mohammad,Shamshad, Bushra,Sultan, Sadaf
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- THE PLATINUM COMPLEX CATALYZED REDUCTIVE CARBONYLATION OF NITROARENE TO URETHANE
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The reductive carbonylation of nitrobenzene to an urethane (ethyl phenylcarbamate) is catalyzed by platinum(II)-tin(IV) systems.The catalytic activities are drastically enhanced by addition of a tertiary amine.
- Watanabe, Yoshihisa,Tsuji, Yasushi,Suzuki, Naoki
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- Synthesis of Amines, Carbamates and Amides by Multi-Step Continuous Flow Synthesis
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We report the continuous flow synthesis of acyl azides in various continuous flow systems and demonstrate that liquid–liquid separation may be incorporated to prepare anhydrous solutions of the acyl azide, which may be subsequently reacted with appropriate nucleophiles to prepare amines, carbamates and amides within a fully integrated multi-step process in high yields (> 80 %). Interesting effects were also observed when preparing carbamates with long chain alcohols, whereby as the chain length of the alcohol increased the products could be made in high yield even without incorporation of the liquid–liquid separation module.
- Sagandira, Cloudius R.,Watts, Paul
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- Selenium-catalyzed oxidative carbonylation of aniline and alcohols to n-phenylcarbamates
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A facile one-pot, phosgene-free synthesis of N-phenylcarbamates is demonstrated. Catalyzed by selenium, oxidative carbonylation of aniline with alcohols in the presence of carbon monoxide and oxygen affords the corresponding N-phenylcarbamates, mostly in fair to good yields. Selenium can be easily recovered because of its phase-transfer catalysis function. Copyright
- Zhang, Xiaopeng,Jing, Huanzhi,Zhang, Guisheng
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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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- Cs2CO3 or CaO as promoters of ethyl N-{[(4-methylphenyl)sulphonyl]oxy}carbamate in amination reactions
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Replacing triethylamine by heterogeneous inorganic bases makes it possible to aminate benzene or other nitrene acceptors, using the title reagent, previously reported to be scarcely reactive. Products of C-H insertion and/or those coming from intermediate aziridines are also obtained.
- Barani, Marco,Fioravanti, Stefania,Pellacani, Lucio,Tardella, Paolo A.
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- Improved amination by ethyl n-(4-nitrophenyl)sulphonyloxy carbamate in the presence of inorganic oxides or carbonates
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Inorganic solid bases give rise to α-elimination reactions of NsONHCO2Et under easy and mild conditions without catalyst or ultrasounds. For several kinds of substrates, a comparison of yields and reaction times with previous methods is presented.
- Barani, Marco,Fioravanti, Stefania,Antonietta Loreto,Pellacani, Lucio,Tardella, Paolo A.
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- Application of Pd(II) Complexes with Pyridines as Catalysts for the Reduction of Aromatic Nitro Compounds by CO/H2O
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Many efforts have been undertaken to minimize the cost of large-scale conversion of aromatic nitro compounds to amines. Toward this end, application of CO/H2O as a reducing agent instead of molecular hydrogen seems to be a promising method, and the process can be catalyzed by Pd(II) complexes. In this work, the catalytic activity of square planar complexes of general structure PdCl2(XnPy)2 (where XnPy = pyridine derivative) was studied. Particular attention was paid to the effects of substituents both in the aromatic ring of XnPy (ligand) and the nitro compound to be reduced (YC6H4NO2). Incorporation of electron-withdrawing Y in the aromatic ring of YC6H4NO2 increases the conversion, indicating that the kinetics of this process is similar to that for the carbonylation of nitrobeznene by CO in the absence of water (described in J. Mol. Catal. A: Chem. 2011, 337, 9-16). Surprisingly, the incorporation of electron-withdrawing substituents into the aromatic ring of the XnPy ligand also increases the conversion of YC6H4NO2 (regardless of the structure of the YC6H4NO2 substrate).
- Krogul, Agnieszka,Litwinienko, Grzegorz
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- Photoinduced Alcoholysis of the Trichloroacetyl Group
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Irradiation of α,α,α-trichloroacetophenone (1a) in methanol afforded alcoholysis products methyl benzoate (2; X=H, R=Me) and methyl benzoylformate (3; X=H, R=Me) along with dichloroacetophenone.Formation of 2 was greatly favored in the presence of oxygen, whereas that of 3 was favored by the sensitization.Quenching studies showed that both alcoholysis products are derived from different excited triplet states.Reaction mechanisms involving the exciplex between 1 and oxygen are discussed.
- Izawa, Yasuji,Tomioka, Hideo,Natsume, Masashi,Beppu, Shinji,Tsujii, Hideo
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- UEBER DIE Si-N-BINDUNG. XLIII. KINETISCHE UNTERSUCHUNGEN ZUR HYDROLYSE VON SILYLURETHANEN DES TYPS (p-XC6H4)Me2SiN(Ph)COOEt
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Hydrolysis reactions of silylurethanes ( p-XC6H4)Me2SiN(Ph)COOEt with X = MeO, Me, H or Cl in aqueous buffer solutions, with pH values from 1.73 to 10.00 and at temperatures of 20, 30, and 40 deg C were studied.The catalytic rate constants for the acid- and base-catalysed reactions and for the "non-catalysed" reaction k(H3O+), k(CH3COO-), k(NH3), k(OH-), and k0 and the Broensted coefficients for the general base-catalysed reactions were evaluated from the pseudo first-order rate constants kexp, determined by UV spectroscopy.The ρ values of the reactions can be derived from the ? constants given by Jaffe.Activation parameters can be obtained by means of the Arrhenius or Eyring equation.From the catalytic constants, Broensted coefficients, ρ values and activation parameters we derive mechanisms for the acid-and general base-catalysed reactions.Conclusions about these mechanisms are compared with the results obtained with the silylurethanes Me3Si(p-XC6H4)NCOOEt.
- Haenig, K.,Grosse-Ruyken, H.,Ruehlmann, K.,Schlapa, J.
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- Direct synthesis of carbamate from CO2 using a task-specific ionic liquid catalyst
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A superbase-derived protic ionic liquid (IL, [DBUH][OAc]) catalyst was used to directly synthesize carbamate from an amine, CO2, and a silicate ester. This IL catalyst was easily prepared using its precursors, DBU, and acetic acid. Using 10 mol% of the catalyst under a CO2 pressure of 5 MPa in acetonitrile at 150 °C, carbamate was isolated in up to 96% yield. Specifically, aliphatic and aromatic amines were activated even though aromatic amines exhibited low activities because of their low pKa values. Other functional groups in amines were barely activated, affording exclusive chemoselectivity for amine activation. Isotope labeling experiments indicated that the proton in the counter cation is crucial in the catalytic cycle to produce water. In addition, a chemical shift corresponding to a mixture of aniline and [DBUH][OAc] was observed in the 1H NMR spectrum, related to the formation of hydrogen bonds between aniline and basic acetate anions. The experimental results indicated that the designed IL catalysts require a protonated cation and a basic anion.
- Zhang, Qiao,Yuan, Hao-Yu,Fukaya, Norihisa,Yasuda, Hiroyuki,Choi, Jun-Chul
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- Copper-Catalyzed Coupling of Amines with Carbazates: An Approach to Carbamates
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A new approach for the preparation of carbamatesviathe copper-catalyzed cross-coupling reaction of amines with alkoxycarbonyl radicals generated from carbazates is described. This environmentally friendly protocol takes place under mild conditions and is compatible with a wide range of amines, including aromatic/aliphatic and primary/secondary substrates.
- Wang, Song-Ning,Zhang, Guo-Yu,Shoberu, Adedamola,Zou, Jian-Ping
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- Multistep continuous-flow microchemical synthesis involving multiple reactions and separations
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(Figure Presented) All for one and one for all: A continuous-flow, multistep microchemical synthesis of carbamates starting from aqueous azide and organic azoyl chloride by using the Curtius rearrangement reaction is described. The procedure involves three reaction steps and two separation steps (one gas-liquid and one liquid-liquid). Formation of a microreactor network for parallel synthesis of analogous compounds is also demonstrated.
- Sahoo, Hemantkumar R.,Kralj, Jason G.,Jensen, Klavs F.
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- Chemical library purification strategies based on principles of complementary molecular reactivity and molecular recognition
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A new methodology for solution-phase chemical library synthesis and purification is described. This approach applies fundamental properties of complementary molecular reactivity and recognition (CMR/R) as the basis for a general purification strategy. Specifically, parallel solution-phase reactions are purified by resins containing molecular recognition or molecular reactivity functionalities complementary to those of solution- phase reactants, reagents, and byproducts. When used in sequential or simultaneous combinations, various CMR/R resins remove excess reactants, reagents, and byproducts from solution-phase reaction products, which are isolated in purified form by filtration. Where reactions involve the need to remove byproducts or reagents that do not inherently contain sequestrable functionality, sequestration can be effected by the design and use of tagged reactants or reagents containing artificially-imparted molecular recognition functionality. An extension of this methodology utilizes CMR/R resins as the 'quench phase' instead of a liquid-phase workup commonly used in other library purification strategies. Hence, the essential features of complementary molecular reactivity or molecular recognition required for reaction workup are expressed on resins. The CMR/R library purification strategy is general and highly amenable to automation. Examples are illustrated with amine acylations, the Moffatt oxidation, and the reaction of organometallics with carbonyl compounds.
- Flynn, Daniel L.,Crich, Joyce Z.,Devraj, Rajesh V.,Hockerman, Susan L.,Parlow, John J.,South, Michael S.,Woodard, Scott
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- Activation of weak nucleophiles: Polyfluorocarbamates from polyfluoroalcohols via a fast radical reaction
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A new fast radical mechanism has been observed for the reaction of polyfluorinated alcohols and phenylisocyanate, very sensitive to the change of solvents and the concentration of reactants. The acidity of polyfluoroalcohols seems to be responsible for the observed new reactivity and evidences from kinetic studies, electron paramagnetic resonance, cyclic voltammetry, and photostimulation suggest that polyfluoroalkoxy radical is the key intermediate in the chain. To the best of our knowledge, it is the first time that a radical mechanism is described for the preparation of carbamates.
- Soto, Marc,Comalrena, Helena,Balduzzi, Ursula,Guirado, Gonzalo,Lloveras, Vega,Vidal-Gancedo, José,Sebastián, Rosa María,Marquet, Jordi
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- One pot synthesis of ureas and carbamates via oxidative carbonylation of aniline-type substrates by CO/O2 mixture catalyzed by Pd-complexes
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Abstract Carbonylation of aromatic amines by direct insertion of carbon monoxide is catalyzed by PdCl2(XnPy)2 complexes (where Py = pyridine, X = -CH3, -Cl; n = 0-2) and gives, depending on the conditions, ethyl N-phenylcarbamates or N,N′-diphenylureas. For carbonylation of aniline, a proper choice of XnPy ligands in PdCl2(XnPy)2 catalyst and application of molecular oxygen instead of nitrobenzene (conventionally used oxidant for carbonylations) allow to carry out the process under mild conditions with high yield and selectivity. The best results (75% yield of the main product with selectivity of catalyst above 90%) were obtained for the process catalyzed by PdCl2(2,4-Cl2Py)2 complex at 100°C and they were greatly improved in comparison to 41% yield and 68% selectivity obtained for CO/nitrobenzene used at 180°C.
- Krogul, Agnieszka,Litwinienko, Grzegorz
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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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- Base-catalyzed synthesis of amides and imines via C-C and CC bond cleavage
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A transition metal free base catalyzed approach for C-N bond formation via C-C and CC bond activation has been developed. The N-arylureas reacted smoothly with 1,3-dicarbonyls and α,β-unsaturated ketones to furnish the corresponding amides and imines respectively in moderate to excellent yields.
- Yadav, Dilip Kumar T.,Bhanage, Bhalchandra M.
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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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- CARBONYLATION OF NITROSOBENZENES TO CARBAMATE ESTERS CATALYZED BY PALLADIUM AND CUPRIC ACETATES UNDER AMBIENT CONDITIONS
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Palladium acetate and cupric acetate are effective catalysts for the reaction of nitrosobenzenes with carbon monoxide and alcohol at room temperature and one atmosphere.
- Alper, Howard,Vasapollo, Giuseppe
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- Direct Catalytic Synthesis of N-Arylcarbamates from CO2, Anilines and Alcohols
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The direct catalytic synthesis of carbamates from CO2, amines and methanol was achieved by controlling both the reaction equilibrium and the reactivity of the three components. The combination of CeO2 and 2-cyanopyridine was an effective catalyst, providing various carbamates including N-arylcarbamates in high selectivities.
- Tamura, Masazumi,Miura, Ayaka,Honda, Masayoshi,Gu, Yu,Nakagawa, Yoshinao,Tomishige, Keiichi
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- Efficient synthesis of methyl carbamate via Hofmann rearrangement in the presence of TsNBr2
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An efficient method has been developed for the synthesis of carbamates from the corresponding amides via the Hofmann rearrangement using N,N-dibromo-p-toluenesulfonamide (TsNBr2) in the presence of DBU in methanol. The reaction goes into completion in 10-20 min at 65 °C to produce the corresponding carbamate in excellent yield.
- Borah, Arun Jyoti,Phukan, Prodeep
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- Halogen-Free Synthesis of Carbamates from CO2 and Amines Using Titanium Alkoxides
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A direct synthesis of carbamates from amines and carbon dioxide in the presence of Ti(OR)4 (R=nBu (1), Me (2), Et (3), nPr (4)) was investigated. Aniline was reacted with titanium n-butoxide (1) in the presence of carbon dioxide (5 MPa) to give the corresponding n-butyl N-phenylcarbamate (BPC) in nearly quantitative yield (99 %) within 20 min. Furthermore, 1 could be regenerated upon reaction with n-butanol during water removal. The recovered 1 could then be reused in a subsequent reaction.
- Choi, Jun-Chul,Yuan, Hao-Yu,Fukaya, Norihisa,Onozawa, Syun-Ya,Zhang, Qiao,Choi, Seong Jib,Yasuda, Hiroyuki
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- PLATINUM COMPLEX CATALYZED REDUCTIVE N-CARBONYLATION OF NITROARENES TO THE CARBAMATES.
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The platinum catalyst combined with triphenylphosphine, tin(IV) chloride, and triethylamine showed high activity for the reductive N-carbonylation of nitroarene in ethanol at 180 degree C under carbon monoxide of 60 kg cm** minus **2. From nitrobenzene, ethyl phenylcarbamate was obtained in 83% yield. Iron(III) chloride, aluminum chloride and titanium(IV) chloride could be used as Lewis acids in place of tin(IV) chloride. Various nitroarenes were transformed into corresponding carbamate in moderate to excellent yields with the platinum catalyst.
- Watanabe,Tsuji,Takeuchi,Suzuki
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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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- 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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- UEBER DIE Si-N-BINDUNG. XLI. KINETISCHE UNTERSUCHUNGEN ZUR HYDROLYSE VON TRIMETHYLSILYLURETHANEN DES TYPS Me3Si(p-XC6H4)NCOOEt
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Hydrolysis reactions of silylurethanes Me3Si(p-XC6H4)NCOOEt (I) with X=Cl, H or Me in aqueous buffer solutions, with pH values from 1.94 to 10.00 were studied.The catalytic rate constants for the acid and base catalysed reactions and for the "non-catalysed" reaction k(H3O+), k(CH3COO-), k(H2PO-4), k(HPO2-4), k(NH3), k(OH-) and k0 were evaluated from the pseudo first-order rate constants kexp determined by UV spectroscopy.The Broensted coefficients for the base-catalysed reactions were obtained from the catalytic rate constants found and the known constants of dissociation K(HB+).The ρ values of the reactions could be derived from the ? constants given by Jaffe.The kinetical results obtained are interpreted mechanistically and are believed to also have model character for other nucleophilic substitution reactions with silicon compounds.
- Grosse-Ryuken, H.,Haenig, K.,Wagner, S.,Ruehlmann, K.,Schlapa, J.
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- Selective Ruthenium Carbonyl Catalysed Reductive Carbonylation of Aromatic Nitro Compounds to Carbamates
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Ru3(CO)12 and Ru(CO)3(PPh3)2 catalyse the reductive carbonylation of aromatic nitro compounds to the corresponding carbamates with high selectivity in the presence of NEt4+Cl- as co-catalyst.
- Cenini, Sergio,Pizzotti, Maddalena,Crotti, Corrado,Porta, Francesca,Monica, Girolamo La
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- Low-energy, Low-temperature Mass Spectra. 10-Urethanes
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The 12.1 eV, 75 deg C electron impact mass spectra of 24 urethanes, RNHCO2C2H5 nH2n+1 (n = 1-8), CH2=CHCH2, Ph, PhCH2 and PhCH2CH2>, and seven symmetrically disubstituted urethanes R2NCO2C2H5 (R = CnH2n+1 (n = 1-4) are reported and discussed.All 31 spectra show appreciable molecular ion peaks.For n-CnH2n+1NHCO2C2H5, M+. usually is the most abundant ion in the spectrum.A peak at m/z 102 of comparable intensity also is present; this corresponds to formal cleavage of the bond connecting the α- and β-carbon atoms in the N-alkyl group, though it is unlikely that the daughter ion has the structure (1+).In the RNHCO2C2H5 series, branching at the α-carbon atom enhances the relative abundance of the ion arising by notional α-cleavage at the expense of that of M+..Formal cleavage of the bond between β- and γ-carbon atoms occurs to some extent for +. ions; this reaction provides information on the degree of branching at the β-carbon, especially if metastable molecular ions are considered.The higher n-CnH2n+1NHCO2C2H5 (n = 5-8) urethanes exhibit two other significant ions in their mass spectra.First, there is a peak at (1+).Secondly, a peak is present at m/z 90; the most plausible structure for this ion is (1+), arising by double hydrogen transfer from the alkyl group and expulsion of a nH2n-1>. radical.Ions originating from secondary decomposition of the primary ionic species are generally of only very low abundance in these spectra.
- Bowen, Richard D.,Maccoll, Allan
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- THE CATALYTIC CARBONYLATION AT ATMOSPHERIC PRESSURE OF PHENYL AZIDE TO PhNCO, PhNHCONHPh AND PhNHCOOEt
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The catalytic activities of rhodium(I) complexes in the carbonylation of phenyl azide at atmospheric pressure, leading to the corresponding isocyanate have been studied. Cl and RhCl(CO)(PPh3)2 are the most active catalysts, and maintain their high activity even in the presence of aniline (which gives diphenylurea) or ethanol (which gives carbamate).
- Monica, Girolamo La,Cenini, Sergio
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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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- The Palladium catalysed Carbonylation of Nitrobenzene into Phenyl Isocyanate: A Metallacyclic Intermediate
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A metallacyclic complex has been isolated from the reaction of PhNO2 with CO using the Palladium(II)-o-phenanthroline system known to produce phenyl isocyanate or carbamates catalytically; reactions of this metallacycle have been studied and its role in the catalytic reaction discussed.
- Leconte, P.,Metz, F.,Mortreux, A.,Osborn, J. A.,Paul, F.,et al.
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- Kinetics of the Mercury(II) Ion-promoted Desulfurisation of Thiocarbamates in Aqueous Solution
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In a 1percent dioxane-water solvent in the presence of Hg2+ ions thiocarbamates p-RC6H4NHC(S)OEt (R = MeO, Me, H, F) rapidly form complexes of 2 thiocarbamate: 1 Hg2+ stoichiometry.In the presence of an excess of Hg2+ ions partial conversion to the 2:2-complexes probably occurs which decompose to the corresponding carbamates (p-RC6H4NHCO2Et) and HgS.With R = NO2 the 2:2 complex is dominant even at low Hg2+ ion concentrations, and desulfurisation is then independent of 2+>.Electron-withdrawal by R favours the 2:2 complex but decreases its rate of decomposition to products.The effects of changes in the hydrogen ion concentration suggest that ionisation of N-bound protons in the complexes favours reaction.A mechanism is suggested.The kinetic behaviour is somewhat similar to that found previously for thiobenzamides, but the new results suggest the mechanism previously proposed may need revision.
- Satchell, Derek P. N.,Satchell, Rosemary S.,Wassef, Wasfy N.
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- Preparation of a novel bromine complex and its application in organic synthesis
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Although molecular bromine (Br2) is a useful brominating reagent, it is not easy to handle. Herein, we describe the preparation of a novel air-stable bromine complex prepared from 1,3-dimethyl-2-imidazolidinone (DMI) and Br2, which was identified to be (DMI)2HBr3 by spectral and X-ray techniques. This complex was then used to brominate olefins, carbonyl compounds, and aromatics, as well as in the Hofmann rearrangement. Yields of reaction products using this complex were almost the same or superior to those using other bromine alternatives.
- Nishio, Yuya,Yubata, Kotaro,Wakai, Yutaro,Notsu, Kotaro,Yamamoto, Katsumi,Fujiwara, Hideki,Matsubara, Hiroshi
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- Transformation of a spirobarbituric acid via aminobarbituric acid-hydantoin rearrangement
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A successful application of the aminobarbituric acid-hydantoin rearrangement to produce a bicyclic carbamoylhydantoin from an intermediate spirobarbituric acid is reported. 7a-Phenylcarbamoyl-tetrahydro-1H-pyrrolo[1,2- c]imidazole-1,3(2H)-dione (8) was obtained in a one-pot multistep reaction of 1-acetyl-2,2-bis(ethoxycarbonyl)pyrrolidine (5) and phenylurea in the presence of sodium ethoxide. Under less severe conditions, 5 and phenylurea were reacted to afford 1-acetyl-7-phenyl-triaza[4,5]decane-6,8,10-trione (6). The structural elucidation of the bicyclic hydantoin 8 and the spirobarbituric acid 6 was based on relevant nmr signals in accordance with those of reference compounds, i.e. monocyclic hydantoins 4a,b and acetamidobarbituric acids 2a-c. The latter compounds were newly prepared from diethyl acetamidomalonates 1 and phenylurea.
- Ambrozak, Agnieszka,Guetschow, Michael
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- Spectroscopic characterization of model urea, urethane compound, and diamine extender for polyurethane-urea
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During the reaction injecting molding process of polyurethane-urea (PUU) based on 4,4′-methylenebisphenyl diisocyanate (MDI), urethane as well as urea linkages are produced when a highly fluorescent aromatic diamine is used as a chain extender. To explore intrinsic fluorescence as a cure characterization technique, model urethane and urea compounds with similar chemical structures to MDI-based PUU were synthesized. Their fluorescence behavior were compared with that of diethyltolunediamine (DETDA), which is often employed as a chain extender. The emission maxima for DETDA in polypropylene oxide (PPO) polyol occurred at 336 nm, while the urea (diphenylurea) and the urethane (ethyl N-phenylcarbamate) model compounds showed emission maxima at 301 and 303 nm, respectively. The relative quantum yield for DETDA was determined to be 57 times greater than the urea compound, while the urethane compound possessed a relative quantum yield 11 times greater than the urea compound. The viscosity effect increased DETDA fluorescence intensity greater than the observed fluorescence intensity decrease associated with a temperature increase of 55°C. DETDA was found to be an effective collisional quencher for the urea and the urethane model compounds. The urea compound does not appear to quench the urethane compound's fluorescence significantly. Study of FT-IR spectra of model urea, urethane compounds, and DETDA provided characteristic peaks for each compound: 1727 cm-1 for urethane, 1647 cm-1 for urea, and 1623.7 cm-1 for DETDA, which were also proportional to their concentration in PPO. NIR spectra of model compounds and DETDA indicate characteristics peaks for the urea, the urethane compounds, and DETDA. However, the urea peak absorbance was difficult to use for quantitative analysis, while the urethane and DETDA peaks could be readily applied for such analysis.
- Wang, Shi-Kwun,Sung, Chong Sook Paik
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- AgF-Mediated Electrophilic Amination of Alkoxyarylsilanes with Azodicarboxylates
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A facile and efficient AgF-mediated electrophilic amination of alkoxyarylsilanes with azodicarboxylates was developed. The reaction proceeds in green solvent under simple and mild conditions to generate the corresponding aryl hydrazines. AgF acts both as a stoichiometric fluoride source and a reagent for transmetalation to the arylsilver intermediate that eventually reacts with azodicarboxylates to provide aryl hydrazines.
- Deng, Shijun,Li, Dong,Shimokawa, Jun,Yorimitsu, Hideki,Zhang, Qian
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- Remarkably Efficient Iridium Catalysts for Directed C(sp2)-H and C(sp3)-H Borylation of Diverse Classes of Substrates
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Here we describe the discovery of a new class of C-H borylation catalysts and their use for regioselective C-H borylation of aromatic, heteroaromatic, and aliphatic systems. The new catalysts have Ir-C(thienyl) or Ir-C(furyl) anionic ligands instead of the diamine-type neutral chelating ligands used in the standard C-H borylation conditions. It is reported that the employment of these newly discovered catalysts show excellent reactivity and ortho-selectivity for diverse classes of aromatic substrates with high isolated yields. Moreover, the catalysts proved to be efficient for a wide number of aliphatic substrates for selective C(sp3)-H bond borylations. Heterocyclic molecules are selectively borylated using the inherently elevated reactivity of the C-H bonds. A number of late-stage C-H functionalization have been described using the same catalysts. Furthermore, we show that one of the catalysts could be used even in open air for the C(sp2)-H and C(sp3)-H borylations enabling the method more general. Preliminary mechanistic studies suggest that the active catalytic intermediate is the Ir(bis)boryl complex, and the attached ligand acts as bidentate ligand. Collectively, this study underlines the discovery of new class of C-H borylation catalysts that should find wide application in the context of C-H functionalization chemistry.
- Chattopadhyay, Buddhadeb,Hassan, Mirja Md Mahamudul,Hoque, Md Emdadul
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supporting information
p. 5022 - 5037
(2021/05/04)
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- Synthesis of 4-substituted-1,2-dihydroquinolines by means of gold-catalyzed intramolecular hydroarylation reaction of n-ethoxycarbonyl-n-propargylanilines
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An alternative Au(I)-catalyzed synthetic route to functionalized 1,2-dihydroquinolines is reported. This novel approach is based on the use of N-ethoxycarbonyl protected-Npropargylanilines as building blocks that rapidly undergo the IMHA reaction affording the 6-endo cyclization product in good to high yields. In the presence of N-ethoxycarbonyl-N-propargyl-metasubstituted anilines, the regiodivergent cyclization at the ortho-/para-position is achieved by the means of catalyst fine tuning.
- Arcadi, Antonio,Calcaterra, Andrea,Fabrizi, Giancarlo,Fochetti, Andrea,Goggiamani, Antonella,Iazzetti, Antonia,Marrone, Federico,Marsicano, Vincenzo,Mazzoccanti, Giulia,Serraiocco, Andrea
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supporting information
(2021/06/21)
-
- Electrophotocatalytic C?H Heterofunctionalization of Arenes
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The electrophotocatalytic heterofunctionalization of arenes is described. Using 2,3-dichloro-5,6-dicyanoquinone (DDQ) under a mild electrochemical potential with visible-light irradiation, arenes undergo oxidant-free hydroxylation, alkoxylation, and amination with high chemoselectivity. In addition to batch reactions, an electrophotocatalytic recirculating flow process is demonstrated, enabling the conversion of benzene to phenol on a gram scale.
- Huang, He,Lambert, Tristan H.
-
supporting information
p. 11163 - 11167
(2021/04/19)
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- N-Aryl and N-Alkyl Carbamates from 1 Atmosphere of CO2
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We have successfully isolated and characterized the zinc carbamate complex (phen)Zn(OAc)(OC(=O)NHPh) (1; phen=1,10-phenanthroline), formed as an intermediate during the Zn(OAc)2/phen-catalyzed synthesis of organic carbamates from CO2, amines, and the reusable reactant Si(OMe)4. Density functional theory calculations revealed that the direct reaction of 1 with Si(OMe)4 proceeds via a five-coordinate silicon intermediate, forming organic carbamates. Based on these results, the catalytic system was improved by using Si(OMe)4 as the reaction solvent and additives like KOMe and KF, which promote the formation of the five-coordinated silicon species. This sustainable and effective method can be used to synthesize various N-aryl and N-alkyl carbamates, including industrially important polyurethane raw materials, starting from CO2 under atmospheric pressure.
- Chen, Ming-Yu,Choe, Yoong-Kee,Choi, Jun-Chul,Fukaya, Norihisa,Hamura, Satoshi,Koizumi, Hiroki,Matsumoto, Kazuhiro,Matsumoto, Seiji,Shigeyasu, Shinji,Takeuchi, Katsuhiko,Yuan, Hao-Yu
-
supporting information
p. 18066 - 18073
(2021/12/08)
-
- A convenient synthesis of thiazol-2(3H)-one skeletons from a reaction involving terminal alkynes, elemental sulfur, and isocyanates
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An efficient copper-catalysed tandem reaction to synthesize thiazol-2(3H)-one structures from readily available raw materials is described. The protocol provides a cost-effective approach to a decent range of nitrogen and sulfur bearing heterocycles in acceptable yields. The transformation takes place with CuCl as catalyst, N-methylpiperidine as additive, and t-BuOK as base in anhydrous DMF as solvent.
- Heydari-Mokarrar, Fahimeh,Heydari, Reza,Maghsoodlou, Malek-Taher,Samzadeh-Kermani, Alireza
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p. 258 - 270
(2020/01/22)
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- Nickel-Catalyzed Synthesis of N-(Hetero)aryl Carbamates from Cyanate Salts and Phenols Activated with Cyanuric Chloride
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A simple and efficient domino reaction has been designed and employed for the one-pot synthesis of N-(hetero)aryl carbamates through the reaction between alcohols and in-situ produced (hetero)aryl isocyanates in the presence of a nickel catalyst. The phenolic C?O bond was activated via the reaction of phenol with cyanuric chloride (2,4,6-trichloro-1,3,5-triazine (TCT)) as an inexpensive and readily available reagent. This strategy provides practical access to N-(hetero)aryl carbamates in good yields with high functional groups compatibility.
- Dindarloo Inaloo, Iman,Esmaeilpour, Mohsen,Majnooni, Sahar,Reza Oveisi, Ali
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p. 5486 - 5491
(2020/09/04)
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- Photocatalyzed synthesis of unsymmetrical ureas via the oxidative decarboxylation of oxamic acids with PANI-g-C3N4-TiO2 composite under visible light
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The synthesis of unsymmetrical ureas via the photocatalyzed oxidative decarboxylation of oxamic acids has been developed. The carbamoyl radicals were generated from oxamic acids in the presence of a hypervalent iodine reagent and the PANI(Polyaniline)-g-C3N4-TiO2 composite under visible light irradiation. The radicals were converted in situ into the corresponding isocyanates, which were then trapped by amines to afford the corresponding products in moderate to good yields. This protocol avoided the direct use of environmentally unfriendly isocyanates and a series of substrates were tolerated. Moreover, the photocatalyst could be readily recovered by simple filtration and be reused for several runs with only a slight decrease in the catalytic activity.
- Wang, Liang,Wang, Hao,Wang, Yaoyao,Shen, Minggui,Li, Shubai
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supporting information
(2020/04/28)
-
- Carbon dioxide utilization in the efficient synthesis of carbamates by deep eutectic solvents (DES) as green and attractive solvent/catalyst systems
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A green and eco-friendly solvent/catalyst system based on a deep eutectic solvent (DES) was devised and developed for the simple synthesis of carbamates through three-component coupling of amines, alkyl halides and carbon dioxide (CO2). It was found that choline chloride:zinc(ii) chloride ([ChCl][ZnCl2]2) was very proficient and effective for the activation and utilization of CO2 in carbamate formation reactions from a wide scope of amines. Surprisingly, this strategy provides the desired carbamates under atmospheric CO2 pressure at room temperature. In particular, both aromatic and aliphatic amines were effective and demonstrated excellent yields. Besides, the [ChCl][ZnCl2]2 exhibited very high stability and also could be reused for at least five consecutive cycles without any significant loss of activity. It is worth noting that this is the first solvent/catalyst system which can be recycled successfully from the reaction mixture.
- Dindarloo Inaloo, Iman,Majnooni, Sahar
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p. 11275 - 11281
(2019/07/31)
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- A Fe3O4?SiO2/Schiff Base/Pd Complex as an Efficient Heterogeneous and Recyclable Nanocatalyst for One-Pot Domino Synthesis of Carbamates and Unsymmetrical Ureas
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A palladium-catalyzed domino method for the direct synthesis of carbamates and ureas has been developed by using readily available and economical starting materials (aryl halide, carbon monoxide, sodium azide, amines and alcohols) in a one-pot approach. The domino process underwent carbonylation, Curtius rearrangement, and nucleophilic addition. This protocol provides a step-economical and highly efficient reaction to access the wide range of valuable carbamates, symmetrical and unsymmetrical ureas with high yields under remarkable mild reaction conditions that are important factors in pharmaceutical science, biochemistry and agricultural industries. Furthermore, the magnetically recoverable nanocatalyst (Fe3O4?SiO2/Pd(II)) can be conveniently and swiftly recycled using external magnet and reused at least for seven times without noticeable loss of its catalytic activity.
- Inaloo, Iman Dindarloo,Majnooni, Sahar
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p. 6359 - 6368
(2019/11/05)
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- An Fe3O4@SiO2/Schiff base/Cu(ii) complex as an efficient recyclable magnetic nanocatalyst for selective mono: N-arylation of primary O-alkyl thiocarbamates and primary O-alkyl carbamates with aryl halides and arylboronic acids
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An efficient, convenient and novel method for the selective mono N-arylation of primary O-alkyl thiocarbamates and primary O-alkyl carbamates with aryl halides and arylboronic acids in the presence of a recyclable magnetic Cu(ii) nanocatalyst is described. A variety of mono N-arylated O-alkyl thiocarbamates and O-alkyl carbamates were prepared in good to excellent yields with a broad range of aryl coupling partners. The magnetic nanocatalyst can be easily recovered with an external magnetic field and reused at least five times without noticeable leaching or loss of its catalytic activity. This cost-effective and eco-friendly methodology has some other advantages, such as easy preparation of the catalyst, simple workup procedure, and easy purification, which makes this protocol interesting for the users in various fields of pharmacology and biotechnology systems.
- Sardarian, Ali Reza,Dindarloo Inaloo, Iman,Zangiabadi, Milad
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p. 8557 - 8565
(2019/06/14)
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- One stone two birds: Cobalt-catalyzed in situ generation of isocyanates and benzyl alcohols for the synthesis of N-aryl carbamates
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An efficient method for the synthesis of N-aryl carbamates from N-Boc-protected amines has been developed. The cobalt-catalyzed in situ generation of isocyanates from N-Boc-protected amines and benzyl alcohols from benzyl formates has been achieved for the first time, which in turn furnished the corresponding benzyl carbamates in moderate to high yields. The reaction was catalyzed by CoI2 with tris-(4-dimethylaminophenyl)-phosphine as the ligand and zinc powder as the reductant. The developed reaction conditions were found to be compatible for aromatic amines with both electron-donating and -withdrawing substituents.
- Li, Sida,Khan, Ruhima,Zhang, Xia,Yang, Yong,Wang, Zheting,Zhan, Yong,Dai, Yuze,Liu, Yue-E,Fan, Baomin
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p. 5891 - 5896
(2019/06/24)
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- An efficient one-pot synthesis of N,N′-disubstituted phenylureas and N-aryl carbamates using hydroxylamine-O-sulfonic acid
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We have developed an efficient one-pot method for the microwave-assisted synthesis of ureas and carbamates via a proposed Lossen rearrangement. Herein we report the first examples of the direct conversion of benzoyl chlorides into N,N′-disubstituted ureas and N-aryl carbamates using hydroxylamine-O-sulfonic acid as reagent. Using our general method, we have produced 11 examples of N,N′-disubstituted phenylureas in yields up to 95% using various substituted anilines, and primary and secondary amines. Additionally, we were able to generate a series of N-aryl carbamates in moderate yields using primary, secondary and tertiary alcohols.
- Bao, Jennifer,Kuik, Dale,Tranmer, Geoffrey K.
-
supporting information
p. 5546 - 5553
(2018/06/12)
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- METHOD FOR PRODUCING CARBAMATE
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PROBLEM TO BE SOLVED: To provide a method for producing carbamate in which a high yield can be obtained and the amount of by-products produced can be reduced. SOLUTION: In the method, carbamate is synthesized using at least one member selected from the group consisting of amine and derivative thereof, alcohol having 3 or more carbon atoms and carbon dioxide as a raw material, cerium oxide as a catalyst, and 2-cyanopyridine as a dehydrating agent. By using an alcohol having 3 or more carbon atoms, a high yield can be obtained and the amount of by-products produced can be reduced. In addition, the pressure of carbon dioxide can be lowered and the production can be of ease. SELECTED DRAWING: Figure 1 COPYRIGHT: (C)2018,JPO&INPIT
- -
-
Paragraph 0041; 0043
(2018/10/16)
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- Ureas as safe carbonyl sources for the synthesis of carbamates with deep eutectic solvents (DESs) as efficient and recyclable solvent/catalyst systems
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A simple, efficient and eco-friendly one-pot synthesis of primary, N-mono- and N-disubstituted carbamates is developed from ureas. The corresponding carbamates were produced at 120 °C, within 18 h, and in the presence of a deep eutectic solvent as a recyclable catalytic system. The catalyst can be reused for several runs without any reduction in its activity. To demonstrate the utility of this approach, a wide variety of alcohols and phenols were studied to find a vast range of carbamate derivatives in moderate to high yields.
- Dindarloo Inaloo, Iman,Majnooni, Sahar
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p. 13249 - 13255
(2018/08/21)
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- Selective Synthesis of Secondary Arylcarbamates via Efficient and Cost Effective Copper-Catalyzed Mono Arylation of Primary Carbamates with Aryl Halides and Arylboronic Acids
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Abstract: An efficient, selective and cost-effective procedure has been developed for mono N-arylation of primary alkyl and benzyl carbamates with aryl iodides and bromides by incorporating CuI as an inexpensive and commercially available catalyst. Despite previous reports on C–N coupling reactions, this process does not need expensive ligands and takes advantage of readily available and inexpensive ethylenediamine (EDA) as the ligand. Reaction times were relatively short and related N-arylated carbamates were obtained in excellent yields. Interestingly, replacing CuI with Cu(OAc)2 allowed us to use arylboronic acids as coupling partner for this reaction. All products are well characterized by 1H- and 13C-NMR, MS, melting point, IR and CHNS techniques.
- Sardarian, Ali Reza,DindarlooInaloo, Iman,Zangiabadi, Milad
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p. 642 - 652
(2018/01/11)
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- Efficient preparation of carbamates by Rh-catalysed oxidative carbonylation: unveiling the role of the oxidant
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The synthesis of a wide variety of carbamates from amines, alcohols and carbon monoxide has been achieved by means of a Rh-catalysed oxidative carbonylation reaction that uses Oxone as a stoichiometric oxidant. In-depth studies on the reaction mechanism shed light on the intimate role of Oxone in the catalytic cycle.
- Iturmendi, Amaia,Iglesias, Manuel,Munárriz, Julen,Polo, Victor,Pérez-Torrente, Jesús J.,Oro, Luis A.
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supporting information
p. 404 - 407
(2017/01/03)
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- Teaching Old Compounds New Tricks: DDQ-Photocatalyzed C?H Amination of Arenes with Carbamates, Urea, and N-Heterocycles
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The C?H amination of benzene derivatives was achieved using DDQ as photocatalyst and BocNH2 as the amine source under aerobic conditions and visible light irradiation. Electron-deficient and electron-rich benzenes react as substrates with moderate to good product yields. The amine scope of the reaction comprises Boc-amine, carbamates, pyrazoles, sulfonimides and urea. Preliminary mechanistic investigations indicate arene oxidation by the triplet of DDQ to radical cations with different electrophilicity and a charge transfer complex between the amine and DDQ as intermediate of the reaction.
- Das, Somnath,Natarajan, Palani,K?nig, Burkhard
-
supporting information
p. 18161 - 18165
(2017/12/28)
-
- A Simple Zinc Catalyst for Carbamate Synthesis Directly from CO2
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Several zinc salts were employed as catalysts for the synthesis of carbamates directly from aromatic amines, CO2, and silicate esters. Zn(OAc)2 offered the best performance among the salts tested. The addition of an N-donor ligand such as 1,10-phenanthroline increased the yield. The best catalytic performance of Zn(OAc)2 can be explained by carboxylate-assisted proton activation. The interaction between the substrate and the catalyst can be observed by chemical shifts in 1H and 15N NMR spectra. Isocyanate was a key intermediate, which was generated from amine and CO2. Silicate ester was finally converted to siloxane, which was determined by 29Si NMR. The commercially available catalyst system could be reused. The yield of isolated carbamate could reach up to 96 % with various substrates, and the catalytic reaction was amine-selective in the presence of other functional groups.
- Zhang, Qiao,Yuan, Hao-Yu,Fukaya, Norihisa,Yasuda, Hiroyuki,Choi, Jun-Chul
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p. 1501 - 1508
(2017/04/14)
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- Synthesis of carbamates from carbon dioxide promoted by organostannanes and alkoxysilanes
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A cooperative methoxy transfer between orthosilicate esters and organotin oxides was developed for the synthesis of various N-alkyl and N-aryl carbamates from carbon dioxide in up to 97% isolated yield. The reaction is highly selective and N-alkylated amines are not observed. Density functional theory calculations of the reaction were performed and, together with NMR observations, a plausible mechanism featuring the catalytic regeneration of dialkyltin dialkoxide is proposed.
- Germain, Nicolas,Hermsen, Marko,Schaub, Thomas,Trapp, Oliver
-
-
- 2 - substituent -5 - substituted anilino - 1, 3, 4 - oxdiazole derivatives and its synthetic method and application
-
The invention discloses a compound 2-substituent-5-substitued anilino-1,3,4-oxadiazole derivative with functions of resisting plant germs and plant viruses and a preparation method and an application thereof, wherein the structure of the compound is represented by the general formula (I). In the invention, the substituted arylamine is adopted as a start raw material, and a thioether compound is prepared by the steps of esterification, hydrazinolysis, salifying, ring closing and etherification; a sulfone compound is prepared by thioether oxidization. The compound disclosed by the invention has a good inhibiting effect on gibberella zeae, pepper fusarium wilt pathogen, valsa mali and tobacco mosaic virus and can be used for preparing medicines resisting plant germs and plant viruses.
- -
-
Paragraph 0093-0094
(2017/04/22)
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- (4-Arylsulfamoyl)phenylcarbamic acid esters: I. Synthesis and activity against herpes viruses
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Aiming to modify the biological activity of sulfonamides, a number of alkyl (4-arylsulfamoyl)- phenylcarbamates were prepared in 50–70% yield. Biological screening showed that the target compounds possessed a high activity against herpes viruses as well as a traditional antibiotic one.
- Krutikov,Erkin,Tets,Shmarov
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p. 1567 - 1573
(2016/08/26)
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- Fe3O4@SiO2/Schiff base/Pd complex as an efficient heterogeneous and recyclable nanocatalyst for chemoselective: N -arylation of O -alkyl primary carbamates
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An efficient, heterogeneous and cost effective method has been developed using an Fe3O4@SiO2/Schiff base/Pd complex as a magnetic and easily recyclable nanocatalyst for rapid and effective N-arylation of carbamates in good to excellent yield. The catalyst can be easily recovered and reused over six runs without significant decrease in the activity. Further highlights of this protocol are operational simplicity, versatility and relatively short reaction times.
- Sardarian,Zangiabadi,Inaloo, I. Dindarloo
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p. 92057 - 92064
(2016/10/11)
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- BMIm HCO3: an ionic liquid with carboxylating properties. Synthesis of carbamate esters from amines
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1-Butyl-3-methylimidazolium hydrogen carbonate (BMIm HCO3) was used as an ionic liquid with carboxylating properties able to convert, in the presence of an alkyl halide, amines into the corresponding carbamate esters. Moderate to good yields of
- Di Nicola,Arcadi,Rossi
-
supporting information
p. 9895 - 9898
(2016/12/07)
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- Copper-catalyzed carbonylation of anilines by diisopropyl azodicarboxylate for the synthesis of carbamates
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A Cu-catalyzed efficient methodology for the direct carbonylation of anilines has been developed. The N-H bond cleavage and N-C bond formation were notably achieved under solvent-free conditions and a variety of carbamates were synthesized from readily available anilines using diisopropyl azodicarboxylate (DIAD) as the carbonylating source.
- Usman, Muhammad,Ren, Zhi-Hui,Wang, Yao-Yu,Guan, Zheng-Hui
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p. 107542 - 107546
(2016/11/29)
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- An efficient one-pot synthesis of: N, N ′-disubstituted ureas and carbamates from N -acylbenzotriazoles
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A facile and high-yielding one-pot synthesis of carbamates and N,N′-disubstituted symmetrical ureas from N-acylbenzotriazoles has been devised. It is believed that, the intermediate acyl-azide undergo Curtius rearrangement and in different solvents gives different products i.e. carbamates in alcohols and N,N′-disubstituted symmetrical urea in THF.
- Singh, Anoop S.,Kumar, Dhananjay,Mishra, Nidhi,Tiwari, Vinod K.
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p. 84512 - 84522
(2016/10/12)
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- One-pot preparation of carbamoyl benzotriazoles and their applications in the preparation of ureas, hydrazinecarboxamides and carbamic esters
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Carbamoyl benzotriazoles were conveniently synthesized in one-pot from carboxylic acids, diphenyl phosphorazidate (DPPA) and 1H-benzotriazole (BtH). The reactivity and applications of carbamoyl benzotriazoles were also explored. Carbamoyl benzotriazoles react smoothly with amino acids, hydrazines and alcohols, thus providing facile access to the corresponding ureas, hydrazinecarboxamides and carbamic esters, respectively, in good to excellent yields.
- Mao, Hui,Liu, Huili,Tu, Yawei,Zhong, Zhiyun,Lv, Xin,Wang, Xiaoxia
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-
- Palladium catalyzed Csp2-H activation for direct aryl hydroxylation: The unprecedented role of 1,4-dioxane as a source of hydroxyl radicals
-
A novel strategy for direct aryl hydroxylation via Pd-catalysed Csp2-H activation through an unprecedented hydroxyl radical transfer from 1,4-dioxane, used as a solvent, is reported with bio relevant and sterically hindered heterocycles and various acyclic functionalities as versatile directing groups.
- Seth, Kapileswar,Nautiyal, Manesh,Purohit, Priyank,Parikh, Naisargee,Chakraborti, Asit K.
-
supporting information
p. 191 - 194
(2015/01/09)
-
- Zinc Triflate Catalyzed C-Benzylation: Chemo- and Regioselective Route to Amido Substituted Diaryl and Arylheteroarylmethanes
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An unprecedented zinc triflate catalyzed selective C-benzylation of anilides and heteroaryl amides with benzyl chlorides having electron-donating group at para-position is reported. The protocol offers moderate to high yield of para-amido substituted diaryl and arylheteroarylmethanes, uses cheap and easily available benzyl chlorides as the benzylating agent, catalytic amount of zinc triflate, and takes place under ambient conditions. Aminodiarylmethane derivatives can be obtained by hydrolysis of the corresponding amides. The methodology has also been applied for preparing dimethoxydiarylmethanes in good yields, which are the key precursors for synthesis of phenolic natural products.
- Deshmukh, Mahesh Subhashrao,Srivastava, Ananya,Das, Biswajit,Jain, Nidhi
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p. 10041 - 10048
(2015/11/03)
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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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- Metal-free reductive cleavage of C-N and S-N bonds by photoactivated electron transfer from a neutral organic donor
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A photoactivated neutral organic super electron donor cleaves challenging arenesulfonamides derived from dialkylamines at room temperature. It also cleaves a)ArC-NR and b)ArN-C bonds. This study also highlights the assistance given to these cleavage reactions by the groups attached to N in (a) and to C in (b), by lowering LUMO energies and by stabilizing the products of fragmentation. Radical fragmentations: Electron transfer from the photoactivated neutral electron donor 1 delivers high yields of S-N and C-N cleavage products for a range of nitrogen-containing species. These reactions proceed at room temperature and under mild reaction conditions in the absence of any metal reagents. DMF=N,N-dimethylformamide, Ts=4-toluenesulfonyl.
- O'Sullivan, Steven,Doni, Eswararao,Tuttle, Tell,Murphy, John A.
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supporting information
p. 474 - 478
(2014/01/23)
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- Aniline carbamates: A versatile and removable motif for palladium-catalyzed directed c-h activation
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The aniline carbamate is introduced as a new removable directing group for C-H activation. Its versatility and ability as a directing group are demonstrated by its use in the ortho-arylation of a wide variety of aniline derivatives under palladium(II) catalysis, with symmetric diaryliodonium salts as aryl donors. The reaction differs from previously reported arylations in its selectivity and its mechanism, as elucidated by kinetic and isotopic experiments. The directing group can also be easily removed under a variety of conditions.
- Uhlig, Nick,Li, Chao-Jun
-
supporting information
p. 12066 - 12070
(2015/03/31)
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- Cu(II)-ion-catalyzed solvolysis of N,N- bis(2-picolyl)ureas in alcohol solvents: Evidence for cleavage involving nucleophilic addition and strong assistance of bis(2-picolyl)amine leaving group departure
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The kinetics and products for solvolysis of N-p-nitrophenyl-N′, N′-bis(pyridin-2-ylmethyl) urea (7a), N-methyl-N-p-nitrophenyl-N′, N′-bis(pyridin-2-yl methyl) urea (7b), and N-phenyl-N′,N′- bis(pyridin-2-yl-methyl) urea (DPPU) (7c) promoted by Cu(II) ion in methanol and ethanol were studied under sspH-controlled conditions at 25 °C. Methanolysis and ethanolysis of these substrates proceeds rapidly at a 1:1 ratio of substrate:metal ion, the half-times for decomposition of the Cu(II):7a complexes being ~150 min in methanol and 15 min in ethanol. In all cases, the reaction products are the Cu(II) complex of bis(2-picolyl)amine and the O-methyl or O-ethyl carbamate of the parent aniline, signifying that the point of cleavage is the bis(2-picolyl) - N - C - O bond. Reactions of the Cu(II):7b complexes in each solvent proceed about 3-5 times slower than their respective Cu(II):7a complexes, excluding an elimination mechanism that proceeds through an isocyanate which subsequently adds alcohol to give the observed products. The reactions also proceed in other solvents, with the order of reactivity ethanol > methanol >1-propanol >2-propanol > acetonitrile (with 0.2% methanol) > water spanning a range of 150-fold. The mechanism of the reactions is discussed, and the reactivity and mode of cleavage are compared with that of the M(II)-promoted ethanolytic cleavage of a mono-2-picolyl derivative, N-p-nitrophenyl-N′-(pyridin-2-yl-methyl) urea (4a), which had previously been shown to cleave at the aniline N-C - O bond. The large estimated acceleration of the rate of attack of ethoxide on 7b of at least 2 × 1016 provided by associating Cu(II) with the departing group in this urea is discussed in terms of a trifunctional role for the metal ion involving Lewis acid activation of the substrate, intramolecular delivery of a Cu(II)-coordinated ethoxide, and metal-ion-assisted leaving group departure.
- Belzile, Mei-Ni,Neverov, Alexei. A.,Brown, R. Stan
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supporting information
p. 7916 - 7925
(2014/08/18)
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- Ceric ammonium nitrate (CAN) catalyzed modification of ketones via two C-C bond cleavages with the retention of the oxo-group
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A simple ceric ammonium nitrate (CAN) catalyzed functionalization of ketones through double C-C bond cleavage strategy has been disclosed. This reaction provides a mild, practical method toward carbamoyl azides, which are versatile intermediates and building blocks in organic synthesis. Based on relevant mechanistic studies, a unique and plausible C-C bond and N-O bond cleavage process is proposed, where the oxyamination intermediate plays an important role in this reaction.
- Feng, Peng,Sun, Xiang,Su, Yijin,Li, Xinyao,Zhang, Li-He,Shi, Xiaodong,Jiao, Ning
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p. 3388 - 3391
(2014/07/08)
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- Microwave-assisted expeditious synthesis of 5-fluoroalkyl-3-(aryl/alkyl)- oxazolidin-2-ones
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An efficient and convenient protocol for synthesis of 5-fluoroalkyl-3- (aryl/alkyl)-oxazolidin-2-ones is described. The reaction of allyl (aryl/alkyl) carbamates with fluoroalkyl iodide initiated by sodium dithionite in aqueous acetonitrile resulted in adducts that undergoes a cyclization assisted by microwave irradiation to form 5-fluoroalkyl-3-(aryl/alkyl)-oxazolidin-2-ones with high yields. It was also found that the products can be more efficiently formed via an AIBN-initiated one-pot addition-cyclization sequence from benzyl allyl(aryl/alkyl) carbamates and fluoroalkyl iodide.
- Yang, Bo,Shi, Luyan,Wu, Jingjing,Fang, Xiang,Yang, Xueyan,Wu, Fanhong
-
supporting information
p. 3331 - 3337
(2013/04/24)
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- Reaction of organozinc halides with aryl isocyanates
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Reformatsky reagent, benzylzinc bromide or alkylzinc iodides react with aryl isocyanates directly to give corresponding N-substituted carbamates under mild reaction conditions. However, the reaction of allylzinc bromide or propargylzinc bromide with aryl isocyanates produces the corresponding N-substituted amides. The reactions provide alternative methods for the synthesis of N-substituted carbamates or amides.
- Yang, Haoran,Huang, Danfeng,Wang, Ke-Hu,Xu, Changming,Niu, Teng,Hu, Yulai
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supporting information
p. 2588 - 2593
(2013/03/28)
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- Design and synthesis of novel stiripentol analogues as potential anticonvulsants
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A series of stiripentol (STP) analogues namely, 2-[(1E)-1-(1,3-benzodioxol- 5-yl)-4,4-dimethylpent-1-en-3-ylidene]-N-(aryl/H)hydrazinecarboxamides 7a-h, (±)-(5RS)-N-(aryl/H)-(1,3-benzodioxol-5-yl)-3-tert-butyl-4, 5-dihydro-1H-pyrazole-1-carboxamides (±)-8a-h, and (±)-[(5RS)-(1, 3-benzodioxol-5-yl)-3-tert-butyl-4,5-dihydro-1H-pyrazol-1-yl](aryl)methanones (±)-13a-f was synthesized by adopting appropriate synthetic routes and was pharmacologically evaluated in the preliminary anticonvulsant screens. The selected bioactive new chemical entities were subjected to ED50 determination and neurotoxicity evaluation. The most active congeners are 7h in MES screen and (±)-13b in scPTZ screen which displayed ED50 values of 87 and 110 mg/kg, respectively, as compared to that of STP (ED 50 = 277.7 and 115 mg/kg in MES and scPTZ, respectively).
- Aboul-Enein, Mohamed N.,El-Azzouny, Aida A.,Attia, Mohamed I.,Maklad, Yousreya A.,Amin, Kamilia M.,Abdel-Rehim, Mohamed,El-Behairy, Mohammed F.
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experimental part
p. 360 - 369
(2012/03/11)
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- Antidepressant activity of carbamates and urea derivatives
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Thirteen (13) compounds of N-phenyl-O-alkyl carbamates (1 and 3), N,N-diethyl-N′-alkyl/aryl/phenylpiperazinoureas (4-6, 8-12), N-phenyl-N′-phenylpiperazino/imidazoureas (2, 7), and N-ethyl-(N′- phenylpiperazino) thioureas 13 were synthesized and tested for their antidepressant-like activity in mice. It was found that compound N-phenyl-O-heptyl carbamate 1 and N-phenyl-N′-phenylpiperazinourea 2 showed 32.5 and 27.7% antidepressant activity in the forced swim test in mice, respectively. Considering other carbamates it was found that a decrease in alkyl chain length caused a marked decline in the antidepressant activity. Compounds 1-4 show even higher activities in the forced swim test than the standard phenelzine. Springer Science+Business Media, LLC 2011.
- Perveen, Shahnaz,Fatima, Nasreen,Khan, Muhammad Aitmaud,Dar, Ahsana,Khan, Khalid M.,Afza, Nighat,Voelter, Wolfgang
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p. 2709 - 2715
(2012/11/06)
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- Preparation of ionic liquid-based vilsmier reagent from novel multi-purpose dimethyl formamide-like ionic liquid and its application
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In continuation of research to explore the applied potential of DMF-like ionic liquid, the ionic liquid version of N,N-dimethyliminiumchloride (Vilsmier reagent) has been synthesized from DMF-like ionic liquid and tested effectively for its capacity to achieve more useful organic transformations. The results show that DMF-like ionic liquid is world's first task specific ionic liquid which has catalyzed numerous diverse type of reaction and is multipurpose in its application. Thus a new term for this DMF-like ionic liquid has been coined that is DMF-like "multipurpose" ionic liquid. Copyright
- Hullio, Ahmed Ali,Mastoi
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scheme or table
p. 1647 - 1657
(2012/09/21)
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