- Unexpected Reaction of Oximinoacetoacetate with Amines: A Novel Synthesis of Carbamates
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The synthesis of alkyl carbamates by a solvent-free reaction of oximinoacetoacetate and amine at 130C is reported. A preliminary mechanism to this unexpected reaction is also given.
- Elghamry, Ibrahim
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- Atomically Dispersed Copper on N-Doped Carbon Nanosheets for Electrocatalytic Synthesis of Carbamates from CO2 as a C1 Source
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The synthesis of carbamates by electrocatalytic reduction of CO2 is an effective method to realize the utilization of CO2 resources. The development of high-performance electrocatalysts to complete this process more efficiently is of great significance to sustainable development. Owing to their unique structural characteristics, single-atom catalysts are expected to promote the reaction process more efficiently. In this study, an atomically dispersed Cu species on N-doped carbon nanosheet composite material (Cu?N?C) was prepared by metal-organic framework derivatization. Compared with traditional Cu bulk electrodes, the Cu?N?C material has better catalytic performance for the synthesis of methyl N-phenylcarbamate; and the optimized yield reached 71 % at room temperature and normal pressure. The Cu?N?C material has good stability that the catalytic performance does not decrease after repeated use for 10 times. In addition, the Cu?N?C material has good applicability to this catalytic system, and a variety of amines can be smoothly converted into corresponding carbamates.
- Li, Shi-Ming,Shi, Yi,Zhang, Jing-Jie,Wang, Ying,Wang, Huan,Lu, Jia-Xing
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- Preparation of methyl carbamates via a modified Hofmann rearrangement
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Treatment of a series of para-substituted aromatic and primary aliphatic carboxamides with NBS and NaOMe in methanol heated to reflux for ten minutes results in the conversion of the carboxamides to their corresponding primary amino methyl carbamates in nearly quantitative yields. The mild oxidative conditions of this modified Hofmann rearrangement are shown to be particularly useful for the preparation of p-substituted anilines.
- Huang, Xicai,Keillor, Jeffrey W.
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- Carbamate synthesis from amines and dimethyl carbonate under ytterbium triflate catalysis
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A facile synthesis of carbamates from amines and dimethyl carbonate has been achieved using ytterbium triflate as catalyst.
- Curini, Massimo,Epifano, Francesco,Maltese, Federica,Rosati, Ornelio
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- CuSe2/CeO2 as a novel heterogeneous catalyst for reductive carbonylation of nitroarenes for generating urethanes
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The reaction of CuCl2, SeO2, and cetyltrimethylammonium bromide (CTAB) under the CO pressure in methanol produce a black solid, which is identified as cupric diselenide, CuIISe2 using various spectroscopic analyses. Impregnation of 5 wt% of CuSe2 onto CeO2 resulted in much more enhanced catalytic activity due to the uniform and highly dispersed particle. The reductive carbonylation of nitrobenzene (NB) as a model substrate has been examined in the presence of the CuSe2/CeO2 as a single component heterogeneous catalyst, which is found to exhibit excellent catalytic activity for generating methyl-N-phenyl carbamate (MPC) in a highly selective fashion. The effects of various reaction parameters such as temperature, pressure, and reaction time have been investigated. A plausible reaction mechanism using this cheap heterogeneous catalyst is also presented, especially invoking the importance of CuSe2(μ-CO) species.
- Tran, Anh Vy,Nguyen, Thanh Tung,Lee, Hye Jin,Bae, Se Won,Baek, Jayeon,Kim, Hoon Sik,Kim, Yong Jin
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- L-Proline-TBAB-catalyzed phosgene free synthesis of methyl carbamates from amines and dimethyl carbonate
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The reaction of amines and dimethyl carbonate (DMC) in the presence of catalytic amounts of l-proline and tetrabutylammonium bromide (TBAB) afforded methyl carbamates in good to excellent yields under mild conditions. The presence of both l-proline and TBAB co-catalysts is vital for this transformation.
- Kumar, Subodh,Jain, Suman L.
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- TBCA mediated microwave-assisted Hofmann rearrangement
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A protocol for the microwave-assisted Hofmann rearrangement mediated by TBCA/KOH/MeOH was developed. Under these conditions high yields and short reaction times were observed for aromatic benzamides.
- Miranda, Leandro S.M.,Da Silva, Thayane Rabello,Crespo, Lívia Tenório,Esteves, Pierre Moth,De Matos, Louise F.,Diederichs, Carla C.,De Souza, Rodrigo Octávio Mendona Alves
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- Reductive Carbonylation of Nitroarenes Using a Heterogenized Phen-Pd Catalyst
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The reductive carbonylation of nitroarenes in the presence of MeOH and CO(g) is one of the interesting alternative routes without utilizing toxic phosgene and corrosive HCl generation for the synthesis of industrially useful carbamate compounds that serve as important intermediates for polyurethane production. Since homogeneous palladium catalysts supported by phen (phen = 1,10-phenanthroline) are known to be effective for this catalysis, the heterogenized Pd catalyst was developed using the phen-containing solid support. In this study, we report the synthesis of a phen-based heterogeneous Pd catalyst, Pd@phen-POP, which involves the solvent knitting of a phen scaffold via the Lewis-acid-catalyzed Friedel-Crafts reaction using dichloromethane as a source for linker in the presence of AlCl3 as a catalyst. The resulting solid material has been thoroughly characterized by various physical methods revealing high porosity and surface area. Similar to the homogeneous pallidum catalyst, this heterogeneous catalyst shows efficient reductive carbonylation of various nitroarenes. The catalytic reaction using nitrobenzene as a model compound presents a high turnover number (TON = 530) and a reasonable turnover frequency (TOF = 45 h-1), with a high selectivity (92%) for the carbamate formation. According to the recycling study, the heterogeneous catalyst is recyclable and retains ~90% of the original reactivity in each cycle.
- Padmanaban, Sudakar,Ganesan, Vinothkumar,Yoon, Sungho,Lee, Yunho
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p. 1552 - 1561
(2022/01/27)
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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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p. 9067 - 9075
(2021/07/19)
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- METHOD FOR PRODUCING CARBAMATE
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PROBLEM TO BE SOLVED: To provide a method that can produce carbamate with high yield and high selectivity, and excellent economical efficiency, using more different kinds of amines. SOLUTION: A method for producing carbamate has a reaction step where, in the presence of calcium carbide and potassium carbonate, a reaction is induced among amine, methanol, and carbon dioxide. The reaction step is preferably performed at a temperature of 165-180°C. The reaction step is preferably performed at a carbon dioxide pressure of 3-5 MPa. The reaction step is preferably performed using an acetonitrile solvent. SELECTED DRAWING: Figure 1 COPYRIGHT: (C)2021,JPOandINPIT
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Paragraph 0014-0024
(2021/08/13)
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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
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supporting information
p. 18066 - 18073
(2021/12/08)
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- Calcium carbide as a dehydrating agent for the synthesis of carbamates, glycerol carbonate, and cyclic carbonates from carbon dioxide
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Carbon dioxide (CO2) is a nontoxic and inexpensive C1 building block, which can be used for the synthesis of valuable chemicals such as aromatic carbamates from anilines and methanol (MeOH), glycerol carbonate from glycerol, and cyclic carbonates from diols. However, these reactions generate water as the byproduct and suffer from thermodynamic limits, which lead to low yields. Calcium carbide (CaC2) is a renewable chemical, which can be recycled from calcium that is abundant in the Earth's crust. Furthermore, CaC2 rapidly reacts with water. In this work, we used CaC2 as a dehydrating agent for the direct synthesis of carbamates (including polyurethane precursors) from amines, CO2, and MeOH. All reagents were commercially available. In addition, CaC2 was employed for the synthesis of glycerol carbonate from glycerol and CO2 with a zinc catalyst and N-donor ligand. A similar protocol was applied to synthesize cyclic carbonates from diols and CO2.
- Choi, Jun-Chul,Fujitani, Tadahiro,Fukaya, Norihisa,Lin, Xiao-Tao,Sato, Kazuhiko,Yuan, Hao-Yu,Zhang, Qiao
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p. 4231 - 4239
(2020/10/02)
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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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p. 1398 - 1405
(2019/02/07)
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- Zr-MOF-808@MCM-41 catalyzed phosgene-free synthesis of polyurethane precursors
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In this work, a catalytic method is presented for the synthesis of aromatic carbamates from aromatic amines using dimethyl carbonate instead of phosgene as a green and safe reaction process. Microcrystalline Zr-MOF-808 is reported as an active and efficient heterogeneous catalyst for the selective carbamoylation of anilines and industrially relevant aromatic diamines, under mild reaction conditions with near quantitative yields. We have accomplished the selective growth of well-dispersed Zr-MOF-808 nanocrystals within the mesoporous material MCM-41. A superior catalytic performance of the Zr-MOF-808@MCM-41 is demonstrated that together with increased stability stands out as an advantageous heterogeneous catalyst for polyurethane production. In situ FTIR studies have allowed a better understanding of the reaction pathway at the molecular level when the active MOF catalyst is present.
- Rojas-Buzo, Sergio,García-García, Pilar,Corma, Avelino
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p. 146 - 156
(2019/01/10)
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- PRODUCTION METHOD OF CARBAMIC ACID ESTER
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A method of production of carbamic acid ester has a high yield and high selectivity and is superior in economy. The method of production of a carbamic acid ester includes reacting an amine, carbon dioxide, and an alkoxysilane compound in the presence of a catalyst containing a zinc compound or an alkali metal compound or in the presence of an ionic liquid. A carbamic acid ester is produced, for example by reacting aniline, carbon dioxide, and tetramethoxysilane at a temperature of 150 to 180° C. in the presence of zinc acetate and 2,2′-bipyridine.
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Paragraph 0048; 0050
(2019/07/03)
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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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p. 4835 - 4839
(2018/10/15)
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- Electrochemical Hofmann rearrangement mediated by NaBr: Practical access to bioactive carbamates
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An electrochemical Hofmann rearrangement is reported. With the mediation of NaBr, highly corrosive and toxic halogens are avoided. Moreover, this efficient and green approach is well compatible with a broad range of amides, including several commercial medicine derivatives, and provides direct access to synthetically useful carbamates. The synthetic utility of this method is also demonstrated by the preparation of 15N labeling carbamate and gram-scale synthesis of Amantadine.
- Li, Lijun,Xue, Mengyu,Yan, Xin,Liu, Wenmin,Xu, Kun,Zhang, Sheng
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supporting information
p. 4615 - 4618
(2018/07/06)
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- Synthesis of N-(Hetero)aryl Carbamates via CuI/MNAO Catalyzed Cross-Coupling of (Hetero)aryl Halides with Potassium Cyanate in Alcohols
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An efficient route to N-(hetero)aryl carbamates was developed through CuI/MNAO [2-((2-methylnaphthalen-1-yl)amino)-2-oxoacetic acid] catalyzed cross-coupling of (hetero)aryl chlorides with potassium cyanate in alcohols at 120-130 °C. This method utilizes
- Kumar, S. Vijay,Ma, Dawei
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p. 2706 - 2713
(2018/03/09)
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- Phosgene-free synthesis of carbamates using co2 and titanium alkoxides
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A facile one-pot, phosgene-free method for the synthesis of N-phenylcarbamates is developed. Using this method, various aromatic carbamates could be prepared from aromatic amines, CO2 and metal alkoxides. Aniline reacted with titanium methoxide (Ti(OMe)4)) in the presence of CO2 (5 MPa) to give methyl N-phenylcarbamate in 85% yield, in 20min. Titanium residue could be regenerated by reaction with dimethyl carbonate at 220 °C for 16 h.
- Yuan, Hao-Yu,Zhang, Qiao,Fukaya, Norihisa,Lin,Fujitani, Tadahiro,Choi, Jun-Chul
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p. 1481 - 1486
(2018/10/25)
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- Rhodium-Catalyzed Oxidative Coupling Reaction of Isocyanides with Alcohols or Amines and Molecular Oxygen as Oxygen Source: Synthesis of Carbamates and Ureas
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The first Rh-catalyzed aerobic oxidative coupling reaction of isocyanides with alcohols or amines has been developed. The reaction takes place under very mild conditions, by using air as the terminal oxidant and oxygen-atom source. It provides a simple, efficient, and general method for the construction of N-arylcarbamates and ureas in an atom-economic manner. Moreover, the new mechanism, involving α-diazocarbonyl compounds as carbene precursors and a RhI/RhIIIcatalytic cycle with oxygen, might open up new avenues in rhodium chemistry.
- Bu, Xiu-Bin,Wang, Zhuo,Wang, Yuan-Hong,Jiang, Tao,Zhang, Lu,Zhao, Yu-Long
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supporting information
p. 1132 - 1138
(2017/03/08)
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- Iodoarene-catalyzed oxidative transformations using molecular oxygen
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Molecular oxygen serves as a useful oxidant for the glycol scission of 1,2-diols and the Hofmann rearrangement of primary amides using pentamethyliodobenzene as a catalyst. The use of isobutyraldehyde and Lewis basic nitriles under O2 enabled the iodine(i)/(iii) catalytic cycle, where in situ-generated peracid acts as a terminal oxidant.
- Miyamoto,Yamashita,Narita,Sakai,Hirano,Saito,Wang,Ochiai,Uchiyama
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supporting information
p. 9781 - 9784
(2017/09/07)
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- 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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- 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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p. 5614 - 5624
(2017/12/06)
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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
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- Palladium-Catalyzed Carbamate-Directed Regioselective Halogenation: A Route to Halogenated Anilines
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This study describes an efficient method for ortho-selective halogenation of N-arylcarbamates under mild conditions for the first time. Although being weakly coordinating, N-arylcarbamates act very well as a removable directing group for activation of C-H bonds. The developed procedure results in extremely valuable halogenated N-arylcarbmates that can further be hydrolyzed to halogenated anilines. The obtained reaction conditions showed broad scope and wide functional group tolerance. All the products were formed in good yields with extremely high selectivity.
- Moghaddam, Firouz Matloubi,Tavakoli, Ghazal,Saeednia, Borna,Langer, Peter,Jafari, Behzad
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p. 3868 - 3876
(2016/05/24)
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- Optimizing ring-opening polymerization of ε-caprolactone by using aluminum complexes bearing amide as catalysts and their application in synthesizing poly-ε-caprolactone with special initiators and other polycycloesters
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A series of aluminum complexes bearing amidate ligands, including acylamide, sulfonamide, and aryl carbamate, was synthesized. In addition, the optimization of ring-opening polymerization of ε-caprolactone by using these aluminum complexes as catalysts was studied. Polymerization results revealed that steric bulky groups in anilinyl groups decreased the catalytic activity of aluminum sulfonamide complexes but increased that of aluminum-acylamide complexes. Compared with other complexes bearing N-(4-methoxyphenyl) acylamidate and N-(4-methoxyphenyl) p-tolylsulfonamidate, an aluminum complex (MfOMeAlMe2) bearing methyl (4-methoxyphenyl)carbamate had the highest catalytic activity with an ideal molecular weight control and narrow polydispersity index (PDI). Other poly-ε-caprolactones with special end chains, such as PEG-200, 2-dimethylaminoethanol, bis(2-hydroxyethyl) disulfide, 2-((2-hydroxyethyl)disulfanyl)ethyl 2-bromo-2-methylpropanoate, and PEG-polyester-bearing disulfide group, were successfully synthesized using MfOMeAlMe2 as the catalyst. The polymerization of δ-valerolactone and 2-bromo-ε-caprolactone by using BnOH as an initiator and MfOMeAlMe2 as the catalyst resulted in poly-δ-valerolactone and poly-2-bromo-ε-caprolactone, respectively, with a precise molecular weight and a narrow PDI as well as poly-ε-caprolactones.
- Tseng, Hsi-Ching,Chen, Fu-Shen,Chiang, Michael Y.,Lu, Wei-Yi,Chen, Yu-Hsieh,Lai, Yi-Chun,Chen, Hsuan-Ying
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p. 90682 - 90690
(2015/11/11)
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- PdCl2 catalyzed efficient assembly of organic azides, CO, and alcohols under mild conditions: A direct approach to synthesize carbamates
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A simple and readily available PdCl2 catalyzed carbamate synthesis method via isocyanate generation and application in situ has been developed. This chemistry provides an efficient and practical approach to synthesize carbamates from simple organic azides, CO atmosphere and alcohols. The broad scope, mild and neutral conditions, and only N2 as the byproduct make this transformation very useful. Moreover, simple examples of modification of bioactive molecules and construction of macrocycles were achieved through this protocol. This journal is the Partner Organisations 2014.
- Ren, Long,Jiao, Ning
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p. 3706 - 3709
(2014/04/03)
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- Synthesis of aryl carbamates via copper-catalyzed coupling of aryl halides with potassium cyanate
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Coupling of aryl halides with potassium cyanate takes place at 100-110 °C in alcohols under the catalysis of CuI (cuprous iodide) and 2-(2,6-dimethylphenylamino)-2-oxoacetic acid, affording the corresponding aryl carbamates with great diversity. Copyright
- Yang, Xinye,Zhang, Yihua,Ma, Dawei
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supporting information
p. 2443 - 2446,4
(2020/08/31)
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- (Tosylimino)phenyl-λ3-iodane as a reagent for the synthesis of methyl carbamates via hofmann rearrangement of aromatic and aliphatic carboxamides
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A new, mild procedure for the Hofmann rearrangement of aromatic and aliphatic carboxamides using (tosylimino)phenyl-λ3-iodane, PhINTs, as a reagent is reported. Because of the mild reaction conditions, this method is particularly useful for the Hofmann rearrangement of substituted benzamides, which usually afford complex reaction mixtures with other hypervalent iodine oxidants. The mild reaction conditions and high selectivity in the reaction of carboxamides with PhINTs allow the isolation of the initially formed labile isocyanates or their subsequent conversion to stable carbamates by treatment with alcohols.
- Yoshimura, Akira,Luedtke, Matthew W.,Zhdankin, Viktor V.
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experimental part
p. 2087 - 2091
(2012/05/05)
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- Nitrogen-containing organobases as promoters in the cobalt(II)-Schiff base catalyzed oxidative carbonylation of amines
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The use of organic bases as promoters in the cobalt(II)-Schiff base complex catalyzed oxidative carbonylation of amines was investigated. The generality of the reaction was also studied by submitting different amines to the same procedure and by changing the reaction conditions. Very good yields in the corresponding ureas were achieved in toluene with a catalyst loading of 0.5 mol % and using TBD (1,5,7-triazabicyclo[4.4.0]dec-5-ene) as promoter. Methyl carbamates were obtained in methanol.
- Saliu, Francesco,Putomatti, Benedetto,Rindone, Bruno
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experimental part
p. 3590 - 3593
(2012/09/08)
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- Palladium-catalyzed carbonylation of amines: Switchable approaches to carbamates and N,N′-disubstituted ureas
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Switchable access to carbamates and ureas has been developed by solvent control palladium-catalyzed carbonylation of aromatic amines under an atmosphere of carbon monoxide. A variety of N-phenylcarbamates and N,N′- diphenylureas was easily synthesized in good to excellent yields from readily available aromatic amines under mild conditions. Copyright
- Guan, Zheng-Hui,Lei, Hao,Chen, Ming,Ren, Zhi-Hui,Bai, Yinjuan,Wang, Yao-Yu
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supporting information; experimental part
p. 489 - 496
(2012/04/04)
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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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experimental part
p. 3035 - 3037
(2012/07/27)
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- Copper-catalyzed coupling of arylboronic acids with potassium cyanate: A new approach to the synthesis of aryl carbamates
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The copper-catalyzed coupling of aromatic boronic acids with potassium cyanate in the presence of an alcohol has been employed for the synthesis of arylcarbamates. This simple and highly efficient approach can be carried out in air at room temperature and, importantly, no base, ligand, or additive is required. Copyright
- Kianmehr, Ebrahim,Baghersad, Mohammad Hadi
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supporting information; experimental part
p. 2599 - 2603
(2011/11/29)
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- Kinetic study of the reactions of methyl 2,4,6-trinitrophenyl carbonate with anilines
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The title reactions in water are subjected to a kinetic investigation. Under excess amine, pseudo-first-order rate coefficients (kobsd) are obtained. Plots of kobsd against aniline concentration are linear, with kN as the slope. The Bronsted-type plot (log kN vs anilinium pK a) is linear with slope 0.7, consistent with a concerted mechanism. By comparison of these reactions with others, it is concluded that anilines destabilize the tetrahedral intermediate relative to isobasic pyridines. The change of 2,4-dinitrophenoxide by 2,4,6-trinitrophenoxide as the leaving group of the carbonate destabilizes the tetrahedral intermediate and makes possible a change in mechanism. ARKAT-USA, Inc.
- Castro, Enrique A.,Aliaga, Margarita E.,Santos, Jose G.
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experimental part
p. 23 - 30
(2011/05/15)
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- Iron(II)-catalyzed oxidation of sp3 C-H bonds adjacent to a nitrogen atom of unprotected arylureas with tert-butyl hydroperoxide in water
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With a FeSO4/TBHP system in water, direct oxidation of sp 3 C-H bonds adjacent to nitrogen of arylureas to give both unprecedented tert-butoxylated and hydroxylated products 2 was revealed. Under elevated temperatures, either 2-oxo-N-arylpyrrolidine-1-carboxamides 3 or 1,3-diarylureas 4 were attained, depending on the aliphatic ring size of the arylurea substrates.
- Wei, Ying,Ding, Hongqian,Lin, Shaoxia,Liang, Fushun
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supporting information; experimental part
p. 1674 - 1677
(2011/05/13)
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- Direct fixation of [11C]-CO2 by amines: Formation of [11C-carbonyl]-methylcarbamates
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[11C-Carbonyl]-methylcarbamates can be synthesised directly from [11C]-CO2 and primary or secondary amines in a one-pot, two-step reaction. The use of either diazabicyclo[5.4.0]undec-7-ene (DBU) or 2-tert-butylimino-2-diethylamino-1,3-dimethyl-perhydro-1,3,2-diazaphosphorine (BEMP) enables efficient trapping of [11C]-CO2 in small volumes of DMF as [11C]-carbamate salts. Subsequent reaction with a variety of methylating agents rapidly generates the desired [ 11C-carbonyl]-methylcarbamates in high radiochemical yields. The usefulness of the method is illustrated by the efficient radiosynthesis of a kappa opioid receptor imaging radiotracer, useful in positron emission tomography (PET).
- Wilson, Alan A.,Garcia, Armando,Houle, Sylvain,Vasdev, Neil
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experimental part
p. 428 - 432
(2010/02/16)
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- Gold-catalyzed phosgene-free synthesis of polyurethane precursors
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(Figure Presented) Golden catalyst: In a two-step one-pot catalytic process gold nanoparticles supported on CeO2 are able to convert nitroaromatics into aromatic carbamates, thereby providing an alternative phosgene-free route towards aromatic polyurethanes (see figure).
- Juarez, Raquel,Concepcion, Patricia,Corma, Avelino,Fornes, Vicente,Garcia, Hermenegildo
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supporting information; scheme or table
p. 1286 - 1290
(2010/05/18)
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- Indium-catalyzed reaction for the synthesis of carbamates and carbonates: selective protection of amino groups
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We developed a simple, efficient, and selective method for preparing organic carbamates and carbonates using a catalytic amount of indium. A wide range of carbamates and carbonates were synthesized in high yields. The method is also applicable to the selective protection of amino groups under mild conditions.
- Kim, Joong-Gon,Jang, Doo Ok
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experimental part
p. 2688 - 2692
(2009/08/09)
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- Hindered ureas as masked isocyanates: Facile carbamoylation of nucleophiles under neutral conditions
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Bigger is better: Sterically hindered dialkyl ureas undergo nucleophilic substitution at dramatically faster rates than their less hindered counterparts (see scheme). Steric decompression upon the formation of an intermediate isocyanate can explain this c
- Hutchby, Marc,Houlden, Chris E.,Gair Ford,Tyler, Simon N. G.,Gagne, Michel R.,Lloyd-Jones, Guy C.,Booker-Milburn, Kevin I.
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supporting information; experimental part
p. 8721 - 8724
(2010/01/16)
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- A microfluidic flow chemistry platform for organic synthesis: the Hofmann rearrangement
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We report on the use of commercially available chemical microreactors to effect the Hofmann rearrangement of aromatic amides to the corresponding carbamates. Crown Copyright
- Palmieri, Alessandro,Ley, Steven V.,Hammond, Kelvin,Polyzos, Anastasios,Baxendale, Ian R.
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scheme or table
p. 3287 - 3289
(2009/08/07)
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- An efficient use of microwave-superoxide combination for the synthesis of organic carbamates and dithiocarbamates
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The present report demonstrates an efficient use of microwave- tetraethylammonium superoxide combination under non-aqueous conditions to bring about a mild and safe carbamation/thiocarbamation of amines, using carbon dioxide/carbon disulfide and methyl iodide.
- Singh, Satish Kumar,Verma, Manjusha,Singh, Krishna Nand
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experimental part
p. 1545 - 1548
(2009/04/07)
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- N-Alkyl-N-alkyloxycarbonylaminomethyl (NANAOCAM) prodrugs of carboxylic acid containing drugs
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Synthesis and hydrolysis in aqueous buffers of novel N-alkyl-N-alkyloxycarbonylaminomethyl (NANAOCAM) and N-aryl-N-alkyloxycarbonylaminomethyl (NArNAOCAM) derivatives of carboxylic acid containing drugs were carried out. The hydrolysis follows a SN1 type mechanism and is dependent on the nucleofugacity of the leaving group. Topical delivery of the NANAOCAM derivative of naproxen from IPM across hairless mice skin was examined in in vitro diffusion cell experiments. The prodrug was 4.5-fold less lipid soluble, 2.4-fold less water soluble and 3.6-fold less permeable than the parent drug.
- Majumdar, Susruta,Sloan, Kenneth B.
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p. 1447 - 1450
(2008/09/21)
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- Mild and convenient synthesis of organic carbamates from amines and carbon dioxide using tetraethylammonium superoxide
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A safe and simple method of preparing organic carbamates has been achieved from amines and carbon dioxide using tetraethylammonium superoxide generated in situ. Copyright Taylor & Francis Group, LLC.
- Singh, Krishna Nand
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p. 2651 - 2654
(2008/02/12)
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- An efficient modification of the Hofmann rearrangement: synthesis of methyl carbamates
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A series of methyl carbamates was synthesized using NaOCl as an oxidant in the presence of KF/Al2O3/MeOH at reflux in excellent yields.
- Gogoi, Pranjal,Konwar, Dilip
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p. 531 - 533
(2007/10/03)
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- Synthesis, hydrolyses and dermal delivery of N-alkyl-N-alkyloxycarbonylaminomethyl (NANAOCAM) derivatives of phenol, imide and thiol containing drugs
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Synthesis, characterization and hydrolysis in aqueous buffers of novel N-alkyl-N-alkyloxycarbonylaminomethyl (NANAOCAM) derivatives of substituted phenols, theophylline (Th) and 6-mercaptopurine (6MP) were carried out. The mechanism of hydrolysis was further investigated by synthesis, characterization and hydrolysis of N-aryl-N-alkyloxycarbonylaminomethyl (NArNAOCAM) derivatives of phenols. The hydrolysis follows pseudounimolecular first order kinetics and operates by way of an SN1-type mechanism. Topical delivery of selected derivatives of acetaminophen (APAP), Th and 6MP was examined in in vitro diffusion cell experiments from IPM across hairless mice skins. The prodrug of APAP and 6MP increased permeation across the skin by about 2- and 4-fold, respectively, compared to the parent drug. NANAOCAM promoieties can act as novel prodrug derivatives of phenol, imide and thiol containing drugs for enhancing topical absorption.
- Majumdar, Susruta,Sloan, Kenneth B.
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p. 3590 - 3594
(2007/10/03)
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- Trapping of carbamic acid species with (trimethylsilyl)diazomethane
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Methoxycarbonylation of a variety of amines into the corresponding methyl carbamates was accomplished by allowing them to react with (trimethylsilyl) diazomethane TMSCHN2 under bubbling of CO2. The reaction was performed at room temperature for a period of ca. 2 h in benzene-MeOH (4/1 v/v), which was the solvent of choice. In this mixed solvent, undesirable bicarbonate is formed in equilibrium along with carbamate anion. Owing to the irreversibility in the esterification step by TMSCHN2, however, the yield of methyl carbamate can reach very high.
- Ito, Yoshikatsu,Ushitora, Hiromi
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p. 226 - 235
(2007/10/03)
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- Selective N,N-dimethylation of primary aromatic amines with methyl alkyl carbonates in the presence of phosphonium salts
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In the presence of onium salts, at 140-170 °C. methyl alkyl carbonates [1a-c, ROCO2Me, R = MeO(CH2)2[O(CH 2)2]n; n = 2-0, respectively] react with primary aromatic amines (XC6H4NH2, X = p-OMe, p-Me, H, p-Cl, p-CO2Me, o-Et, and 2,3-Me2C 6H3NH2) to yield the corresponding N,N-dimethyl derivatives (ArNMe2) with high selectivity (up to 96%) and good isolated yields (78-95%). Phosphonium salts (e.g., Ph3PEtI and n-Bu4PBr) are particularly efficient catalysts. Overall, a solvent-free reaction is coupled with safe methylating agents (1a-c) made from nontoxic dimethyl carbonate.
- Selva, Maurizio,Perosa, Alvise,Tundo, Pietro,Brunelli, Davide
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p. 5770 - 5773
(2007/10/03)
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- The methoxycarbonylation of aryl chlorides catalysed by palladium complexes of bis(di-tert-butylphosphinomethyl)benzene
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A catalyst system based on palladium-1,2-bis-(di-tert-butylphosphinomethyl) benzene (BDTBPMB) shows good activity for the methoxycarbonylation of strongly activated aryl chlorides, like 4-chloromethylbenzoate or 4-chlorocyanobenzene. Surprisingly, the use of less activated aryl chlorides, like 4-chloroacetophenone, leads to the formation of dimethyl terephthalate amongst other products arising from organic reactions of methoxide ion and/or CO. Less nucleophilic alcohols such as 2,2,2-trifluoroethanol promote the formation of carbonylation products even from 4-chloroacetophenone and chlorobenzene. Labelling studies involving CD3OH, CD3OD or 13CO give information on the origin of many of the products. The Royal Society of Chemistry 2005.
- Jimenez-Rodriguez, Cristina,Eastham, Graham R.,Cole-Hamilton, David J.
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p. 1826 - 1830
(2007/10/03)
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- Synthesis of mono-N-substituted functionalized anilines
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The present invention relates to a process for direct and selective synthesis of mono-N-substituted functionalized anilines by using alkylating agents selected from the class of organic carbonates, preferably of the dialkyl, dibenzyl and diallyl types, in the presence of suitable catalysts that are chemically related to the class of aluminosilicates.
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- Polymer-immobilized gold catalysts for the efficient and clean syntheses of carbamates and symmetric ureas by oxidative carbonylation of aniline and its derivatives
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A series of highly efficient polymer-immobilized gold catalysts were prepared for the oxidative carbonylation of aniline and its derivatives to obtain carbamates and symmetric ureas in a clean, simple, solvent-free, and obtainable product-ready way. TEM showed that the average gold particle size of fresh catalyst was less than 10 nm.
- Shi, Feng,Deng, Youquan
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p. 548 - 551
(2007/10/03)
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