- 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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- 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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p. 2050 - 2055
(2021/03/24)
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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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- 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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- Oxidative Photochlorination of Electron-Rich Arenes via in situ Bromination
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Electron-rich arenes are oxidatively photochlorinated in the presence of catalytic amounts of bromide ions, visible light, and 4CzIPN as organic photoredox catalyst. The substrates are brominated in situ in a first photoredox-catalyzed oxidation step, followed by a photocatalyzed ipso-chlorination, yielding the target compounds in high ortho/para regioselectivity. Dioxygen serves as a green and convenient terminal oxidant. The use of aqueous hydrochloric acid as the chloride source reduces the amount of saline by-products.
- Düsel, Simon Josef Siegfried,K?nig, Burkhard
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supporting information
p. 1491 - 1495
(2019/04/30)
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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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- Methoxycarbonylation of Alkyl-, Cycloalkyl-, and Arylamines with Dimethyl Carbonate in the Presence of Binder-Free Zeolite
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Abstract: Methyl N-alkyl-, N-cycloalkyl-, and N-arylcarbamates were synthesized by reaction of the correspondingamines with dimethyl carbonate in the presence of binder-free FeHY zeolite. Theoptimal conditions (reactant ratio, amount of the catalyst, temperature,reaction time) were found to afford the target products with high yields.
- Khazipova, A. N.,Khusnutdinov, R. I.,Mayakova, Yu. Yu.,Shchadneva, N. A.
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p. 1228 - 1235
(2020/10/02)
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- PRODUCTION METHOD FOR AMIDATE COMPOUND
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A method for producing an amidate compound represented by Formula (3), comprising reacting a urethane compound represented by Formula (1) with a carboxylate compound represented by Formula (2): (in the formulas, A, n, R1, R2, R3, R4, R5, R6, X, and a are as described in the Description).
- -
-
Paragraph 0174-0176
(2020/02/13)
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- Amidate compound, catalyst for polyurethane production, and method for producing polyurethane resin
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Provided is an amidate compound represented by the formula (1): wherein A is a substituted or unsubstituted hydrocarbon group, n is an integer of 1 or more, and D is a nitrogen-containing organic group represented by the formula (2): wherein R1, R2, and R3 are the same or different, and are each a hydrocarbon group that may contain a heteroatom; some or all of R1, R2, and R3 may be bonded together to form a ring structure; X is a nitrogen atom, an oxygen atom, or a sulfur atom; and a is 0 or 1, wherein a is 1 when X is a nitrogen atom, and a is 0 when X is an oxygen atom or a sulfur atom.
- -
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Page/Page column 130
(2020/07/09)
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- Interaction of dimethyl carbonate with anilines in the presence of potassium methylate: Kinetics and the role of the base
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The kinetic patterns of the reaction between dimethyl carbonate and anilines in the presence of a potassium methylate as a catalyst were studied. The mechanism of aminolysis was clarified, which includes the detachment of the proton from the amino group of aniline and the subsequent attack of the resulting anion on the carbonyl group of dimethyl carbonate. It is shown that when the reaction occurs in the dimethyl carbonate-methanol 3:1 system, the process can be described as an irreversible first-order reaction in the aniline though the target reaction is complicated by side interaction between potassium methylate and dimethyl carbonate. The rate constants of the target reaction with substituted anilines and of the side reaction in the temperature range of 70-90°C were determined. It is shown that the influence of the substituent on the reaction rate is described by the Hammett equation, with the constant of the reaction series being positive and the best correlation being achieved for ??-scale. The results obtained are consistent with the proposed mechanism of the reaction and are explained by the facilitation of the aniline deprotonation with increasing acceptor properties of the substituent. Effective activation energies for the reaction of various anilines with dimethyl carbonate are found.
- Mantrov, Sergey N.,Gordeev, Dmitry A.,Dashkin, Ratmir R.,Nefedov, Pavel A.,Seferyan, Mary A.
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p. 777 - 785
(2019/08/07)
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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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- 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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- Selective N-monomethylation of primary anilines with dimethyl carbonate in continuous flow
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Selective N-monomethylation of anilines has been achieved under continuous flow conditions using dimethyl carbonate as a green methylating agent in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene. Our methodology takes advantage of the expanded process windows available in the continuous flow regime to safely induce monomethylation in superheated solvents at high pressure. We propose selective N-monomethylation is achieved via an in situ protection-deprotection pathway, which is supported by the observed reactivities of several putative reaction intermediates. The robust and scalable method was applicable to a broad range of primary aniline substrates including ortho-, meta-, and para-substituted anilines, as well as electron-rich and electron-deficient anilines. The synthetic precursor of diazepam, 5-chloro-2-(methylamino)benzophenone, was selectively synthesized under our optimized conditions.
- Seo, Hyowon,Bédard, Anne-Catherine,Chen, Willie P.,Hicklin, Robert W.,Alabugin, Alexander,Jamison, Timothy F.
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p. 3124 - 3128
(2017/12/11)
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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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- 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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- A synthetic approach to N -aryl carbamates via copper-catalyzed Chan-Lam coupling at room temperature
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A mild and efficient synthesis of N-arylcarbamates was achieved by reacting azidoformates with boronic acids in the presence of 10 mol % of copper chloride catalyst. The reaction proceeds readily in an open flask at room temperature without additional base, ligand, or additive. Rapid access to urea analogues via a two-step one-pot procedure is enabled by reacting N-arylcarbamates with aluminum-amine complexes. In addition, among several boronic acid derivatives prepared, dimethylphenyl boronate was found to react rapidly in its reaction with benzyl azidoformate, invoking in situ generation of this species in the catalytic cycle.
- Moon, Soo-Yeon,Kim, U. Bin,Sung, Dan-Bi,Kim, Won-Suk
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p. 1856 - 1865
(2015/02/19)
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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
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supporting information
p. 12066 - 12070
(2015/03/31)
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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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p. 2935 - 2938
(2013/09/12)
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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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- 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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- 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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scheme or table
p. 3590 - 3593
(2012/09/08)
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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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p. 2087 - 2091
(2012/05/05)
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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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supporting information; experimental part
p. 1639 - 1640
(2011/04/26)
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- Synthesis of methyl-1-(tert -butoxycarbonylamino)-2- vinylcyclopropanecarboxylate via a hofmann rearrangement utilizing trichloroisocyanuric acid as an oxidant
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A trichloroisocyanuric acid (TCCA) mediated Hofmann rearrangement was utilized to synthesize methyl-1-(tert-butoxycarbonylamino)-2- vinylcyclopropanecarboxylate. A variety of functional groups are tolerated in this reaction including vinyl, cyclopropyl, pyridyl, aryl, benzyl, and nitro groups.
- Crane, Zackary D.,Nichols, Paul J.,Sammakia, Tarek,Stengel, Peter J.
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supporting information; experimental part
p. 277 - 280
(2011/03/20)
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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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- Green and practical synthesis of carbamates from ureas and organic carbonates
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A practical method for the synthesis of carbamates from ureas and organic carbonates was developed with 100% atom economy using La2O 3/SiO2 as catalyst without any additional solvent. The scope of the protocol is demonstrated in the synthesis of 14 carbamates with various functional groups in excellent yields (76-95%).
- Guo, Xiaoguang,Shang, Jianpeng,Li, Jian,Wang, Liguo,Ma, Yubo,Shi, Feng,Deng, Youquan
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experimental part
p. 1102 - 1111
(2011/05/02)
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- Atom-economy synthesis of N-substituted carbamate from urea derivative and dimethyl carbonate catalyzed by La/SiO2: Characterization and activity
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A series of silica gel immobilized lanthanum catalysts were prepared for the atom-economy synthesis of N-substituted carbamates from urea derivatives and dimethyl carbonate. The La/SiO2 catalysts with lanthanum loadings varied from 1.3 wt% to 8.5 wt% were characterized by AES, BET, XRD, TEM, FT-IR, XPS and TPD. According to the characterization, lanthanum species with particle sizes of 5-10 nm on the surface of silica gel were formed. The catalysts were all amorphous and the surface areas were 336.5-530.2 m2/g. NH3-TPD analysis showed that all samples exhibited similar acid strength with different acid amounts. FT-IR measurement indicated that the component of lanthanum species on the catalyst surface were La(OH)3, LaOOH and hydrated La2O3. Also, the peak value of the absolute amount of LaOOH was obtained with 4.3 wt% lanthanum loading. The BET surface area decreased dramatically when the lanthanum loading was above 4.3 wt%. In consideration of the results obtained from the catalytic reactions, it could be concluded that LaOOH was the possible active species and high surface area was important for the high catalytic activity.
- Guo, Xiaoguanga,Shang, Jianpenga,Li, Jiana,Wang, Liguoa,Ma, Yuboa,Shi, Feng,Deng, Youquan
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experimental part
p. 164 - 170
(2010/10/19)
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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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- 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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- Efficient palladium/1,10-phenanthroline-catalyzed reductive carbonylation of mono- and dinitroarenes to urethanes in phosphonium salt ionic liquids
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(Chemical Equation Presented) The highly reactive and selective reductive carbonylation of mono- and dinitroarenes to the corresponding mono- and diurethanes was carried out in the presence of a PdCl2/Phen catalytic system, using PSIL110[C14H29(C6H 13)3P+PF6-] as the ionic liquid under mild reaction conditions. No cocatalyst is required.
- Yang, Qian,Robertson, Al,Alper, Howard
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experimental part
p. 5079 - 5082
(2009/05/07)
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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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- 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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- 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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- An environmentally benign access to carbamates and ureas
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Ureas were synthesized from methyl carbamates which were obtained by reaction of amines with dimethylcarbonate. Both reactions were catalyzed by γ-A12O3. (C) 2000 Elsevier Science Ltd.
- Vauthey,Valot,Gozzi,Fache,Lemaire
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p. 6347 - 6350
(2007/10/03)
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- Synthesis of functionalized carbamates through a palladium-catalyzed reductive carbonylation of substituted nitrobenzenes
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The palladium-catalyzed reductive carbonylation of ortho and para-substituted nitrobenzenes has proven to be an attractive route for the synthesis of functionalized carbamates. For the Pd(1,10-phenanthroline)2(triilate}2 catalyst system, the scope of the reaction has been studied. Substrates with electron-donating substituents at the para position were found to decrease the catalytic activity, most probably as a result of their relatively low oxidizing capacity. The selectivity towards the desired carbamate, however, was increased for these substrates. Under the influence of electron-withdrawing substituents the azoxybenzene and azobenzene derivatives became important side products. Introduction of large steric hindrance at the ortho position of the nitro substrates gave rise to an interesting side reaction, viz. methoxylation of the aromatic ring. The methoxylation reaction appeared to occur on an intermediate species in the catalytic cycle. Several functionalities have shown to be resistant to the reaction conditions required for the conversion of the nitro group. Especially with 4-nitrobenzoic acid, an extremely high activity and selectivity was found, thus yielding a very convenient synthesis for N-protected amines containing carboxylic acid functions. VCH Verlagsgesellschaft mbH.
- Wchman, Petra,Borst, Leo,Kamer, Paul C. J.,Van Leeuwen, Piet W. N. M.
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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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p. 313 - 316
(2007/10/03)
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- Indirect electrochemical carbonylation of aromatic amines with a palladium catalyst
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Aromatic amines are converted to carbamates under very mild conditions, using carbon monoxide, palladium (II) acetate and copper (II) acetate in combination with anodic reoxidation.
- Hartstock, Frederick W.,Herrington, Deborah G.,McMahon, Launa B.
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p. 8761 - 8764
(2007/10/02)
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- Carbamoyl complexes as a source of isocyanates or carbamyl chlorides
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Isocyanates or carbamyl chlorides have been prepared by reaction of carbamoyl complexes of nickel and palladium with CuCl2.Isocyanates are selectively produced from the carbamoyl complexes of primary amines, , (L=2,6-bis(diphenylphosphinomethyl) pyridine; R=C6H5, p-CH3C6H4, or p-ClC6H4)) and , whereas carbamoyl complexes of secondary amines, such as , afford carbamyl chloride.As expected, the reaction of the resulting isocyanates or carbamyl chlorides in situ with alcohols or amines produces carbamates or N,N'-substituted ureas, respectively.Key words: Carbamyl chloride; Carbamate; Carboxamide; Chloroformamide; Complex; Isocyanates; Palladium; Phosphine; Synthesis
- Giannoccaro, Potenzo,Tommasi, Immacolata,Aresta, Michele
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- A process for the preparation of carbamates
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A process for preparing carbamates having the general formula I: wherein R1 represents a hydrogen atom or an alkyl group, R2 represents an optionally substituted aryl group and R3 represents an alkyl, haloalkyl, alkenyl, haloalkenyl, alkynyl, haloalkynyl
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- Ring Cleavage Reaction of 1,3-Oxazine-2,4(3H)-dione Derivatives with Amines
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The reactions of 3,6-dimethyl -1,3-oxazine-2,4(3H)-diones (1a, 1b, and 1c) with various amines were investigated under various conditions.Several reactions products were obtained such as the pyrimidines (3a, 3b, 3c, and 3d), the acetoacetamides (4a, 4b, and 4c), (4-chlorophenyl)urethane (5a), and ethyl acetoacetate (4d) with primary amines, and the acetoacetamides (4e and 4f), the urethanes (5a and 5b), the carboxamides (5c, 5d, 5e, and 5f), and the butenamides (7a, 7b, and 7c) with secondary amines.In the case of 1c with amine, alcohol used as a solvent reacted as a nucleophile to give the urethane (5a or 5b).
- Kinoshita, Toshio,Takeuchi, Kozue,Kondoh, Masaya,Furukawa, Sunao
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p. 2026 - 2029
(2007/10/02)
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- Halogenation Using Quatenary Ammonium Polyhaloides. IX. One-Step Syntheses of Acylureas and Carbamates from Amides by Use of Tetrabutylammonium Tribromide and DBU
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The reaction of amides with tetrabutylammonium tribromide (TBA Br3) (0.5 equiv) and DBU (one equiv) in dichloromethane at room temperature gave N-substituted acylureas in fairly good yields.In the presence of alcohols, the reaction of amides with TBA Br3 (one equiv) and DBU (two equiv) gave N-substituted carbamates.
- Fujisaki, Shizuo,Tomiyasu, Kazushi,Nishida, Akiko,Kajigaeshi, Shoji
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p. 1401 - 1403
(2007/10/02)
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- Azepinoindole Synthesis from a 1,2,3,4-Tetrahydro-9(10H)-acridinone and Sodium Dichloroisocyanurate or Singlet Oxygen
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Sodium dichloroisocyanurate (4) acts on 7-methyl-1,2,3,4-tetrahydro-9(10H)-acridinone (1) to give principally either cis-1,2-diol 2 or azepinoindole 3, by suitable choice of reactant proportions. 2,3,6-Trimethyl-4(1H)-quinolinone (6) yields a novel, methylene-bridged, oxygenated dimer 9, while with excess 4 the chief product is the 1,2-dihydro-3H-indol-3-one 7. 6-Methyl-2-phenyl-4(1H)-quinolinone (12) initially gives the 3-chloro derivative 14, which then reacts further with 4, yielding chlorine-free 6-methyl-2-phenyl-4H-3,1-benzoxazin-4-one (16).The sensitized photooxidation of acridinone 1 furnishes azepinoindole 3 en route to dicarboxylic acid 5; upon similar treatment, quinolinone 6 provides the analogous indolone 7.Reaction pathways to account for the results are presented.N-Halo imide 4 offers advantages over the more conventional NaOCl in synthesis as illustrated also with a "one-pot" Hofmann degradation of 4-chlorobenzamide.
- Staskun, Benjamin
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p. 5287 - 5291
(2007/10/02)
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- An Exceptionally Mild, Catalytic Homogeneous Method for the Conversion of Amines into Carbamate Esters
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Aromatic amines react at room temperature and atmospheric pressure with carbon monoxide, oxygen, alcohols, and hydrochloric acid, with palladium chloride as the catalyst and copper(II) chloride as re-oxidant to give carbamate esters in fair to quantitative yields.
- Alper, Howard,Hartstock, Frederick W.
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p. 1141 - 1142
(2007/10/02)
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