- Self-assembly of ionic liquids and metal complexes in super-cages of NaY: Integration of free catalysts and solvent molecules into confined catalytic sites
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The integration of a free metal complex, Pd(phen)2+, and a room temperature ionic liquid (IL) solvent molecule, 1-decyl-3-methyl imidazolium bromide, into a complete catalytically active site and confined in a NaY zeolite super-cage with an appropriate spatial arrangement was investigated. This integration was achieved through a molecular self-assembly method. A preliminary test of this catalyst system for the carbonylation of aniline to methyl phenyl carbamate indicated that far higher catalytic activity could be achieved (TOF increased from 3 000 to 23 000 h-1) with far lower amounts of the IL solvent and the Pd complex in comparison with a simple mixture of Pd(phen)Cl2/IL/NaY as the catalyst. This new system can also be applied to other areas of catalysis.
- Ma, Yubo,He, Yude,Zhang, Qinghua,Shi, Feng,Ma, Xiangyuan,Lu, Liujin,Deng, Youquan
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- -, -, and bimetallic clusters as catalysts for carbonylation of nitrobenzene to methyl phenylcarbamate
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Bimetallic clusters of the general formula 2 (M = Fe, Ru, or Os; PPN- = (PPh3)2N+) are active catlysts in the presence of methanol for the carbonylation of nitrobenzene to methyl phenylcarbamate.The clusters are active even without co-catalyst, but the addition of bipy (2,2'-bipyridine) greatly enhances both rates and selectivities.In the absence of methanol the conversion was much lower, with a low selectivity in phenyl isocyanate.Interchanging Fe, Ru, and Os has a negligible effect on the activity and a moderate effect on the selectivity, with ruthenium being best.However, the monometallic rhodium cluster - proved to be both more active and selective, and the monomer - was found to be even better.This last catalytic system has been optimized with respect to temperature, CO pressure and the bipy/Rh ratio.The influence of solvent was also examined.
- Ragaini, Fabio,Cenini, Sergio,Fumagalli, Alessandro,Crotti, Corrado
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- Oxidative carbonylation of aniline with a mesoporous silica gel immobilised Se-functionalised ionic liquid catalyst
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A series of BMImBF4-templated mesoporous silica gel immobilised Se-functionalised ionic liquids have been prepared. The catalysts were characterised by BET, FTIR and ICP-AES, and the results showed that the content of Se increased from 2.7 to 4.76 wt% with pore volume increasing from 0.83 to 1.26 cm3 g-1. Preliminary tests of this catalyst system on the carbonylation of aniline to afford methyl phenyl carbamate (MPC) indicated that good catalytic activity (higher than 74% aniline conversion with 99% MPC selectivity) could be achieved with higher than 150 mol h-1 mol -1 turnover frequency (TOF). TOF and aniline conversion slightly increased with increasing the content of Se from 2.7 to 3.0 wt%, then decreased when the content of Se increased to more than 3.0 wt%, this suggested that 2.7 to 3.0 wt% Se content should be appropriate for MPC synthesis. The appropriate Se content could be obtaineded by adjusting the range of pore volume of mesoporous silica gel from 0.83 to 0.85 cm3 g-1. In addition, the recycling test indicated that there was almost no deactivation of the catalyst when it was reused four times.
- Ma, Yubo,Shi, Feng,Deng, Youquan
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- The Induction Period and Novel Active Species in Zn(OAc)2 Catalyzed Synthesis of Aromatic Carbamates
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Abstract: Zn(OAc)2 is known to exhibit excellent catalytic activity for aromatic carbamate synthesis by the reaction of aromatic amine and dimethyl carbonate (DMC). It is determined that an induction period exists during the synthesis of dimethyl-4,4′-methylenediphenyl dicarbamate (MDC) and methyl N-phenyl carbamate (MPC), although this period is more evident in the case of MDC. Zn(OAc)2 is able to catalyze the reaction of amine and DMC, but also react with DMC to form Zn4O(OAc)6, which also shows excellent catalytic activity for carbamate synthesis. As for MDC synthesis, Zn4O(OAc)6 plays the important role. However, Zn(OAc)2 plays the leading role in MPC synthesis. The deactivation of Zn4O(OAc)6 was also investigated. Zn4O(OAc)6 was initially transformed into Zn5(OH)8(OAc)2·2H2O (LHZA) and then into ZnO. Graphical Abstract: [Figure not available: see fulltext.].
- Li, Fang,Wang, Xi,Li, Hongqin,Wang, Shufang,Xue, Wei,Wang, Yanji
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- Determination and modeling of isobaric vapor-liquid equilibria for the methylcarbamate + Methyl-N-phenyl carbamate system at different pressures
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The vapor pressures of methylcarbamate (MC) and methyl n-phenyl carbamate (MPC), at different temperatures ranging from (341.45 to 418.45) K, have been measured using the quasi-static ebulliometric method. The experimental data were fitted to the Antoine
- Xu, Dehua,Li, Huiquan,Li, Zhibao
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- The carbonylation reaction of nitrobenzene to methyl phenylcarbamate: Highly efficient promoters for the palladium-phenanthroline catalytic system based on phosphorus acids
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Phenomenal! The activity of the palladium-phenanthroline catalytic system for the carbonylation of nitrobenzene to methyl phenylcarbamate is greatly enhanced by the addition of phosphorus acids. Of those that were studied, the best promoter is the very cheap, easily separable, and nontoxic phosphoric acid.
- Ragaini, Fabio,Cognolato, Carlo,Gasperini, Michela,Cenini, Sergio
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- Highly selective phosgene-free carbamoylation of aniline by dimethyl carbonate under continuous-flow conditions
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Over the last 20 years organic carbamates have found numerous applications in pesticides, fungicides, herbicides, dyes, pharmaceuticals, cosmetics, and as protecting groups and intermediates for polyurethane synthesis. Recently, in order to avoid phosgene-based synthesis of carbamates, many environmentally benign and alternative pathways have been investigated. However, few examples of carbamoylation of aniline in continuous-flow apparatus have been reported. In this work, we report a high-yielding, dimethyl carbonate (DMC)-mediated carbamoylation of aniline in a fixed-bed continuously fed reactor employing basic zinc carbonate as catalyst. Several variables of the system have been investigated (i.e. molar ratio of reagents, flow rate, and reaction temperature) to optimize the operating conditions of the system.
- Grego, Sandra,Aricoi, Fabio,Tundo, Pietro
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- Alternative, easy and efficient preparation of poly[4-(diacetoxyiodo) styrene] from poly(4-iodostyrene) using sodium perborate as the oxidant
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An operationally simple, efficient, and considerably improved preparative procedure of poly[4-(diacetoxyiodo)styrene] (PSDIB) is reported. This procedure is performed with acetic acid, 1,2-dichloroethane, commercially available sodium perborate tetrahydrate as an oxidant, and triflic acid as an additive, and gives PSDIB after a short reaction time. PSDIB is employed as an oxidiz-ing agent in organic synthesis and can be regenerated and reused in the same reaction. Georg Thieme Verlag Stuttgart.
- Hossain, Md. Delwar,Kitamura, Tsugio
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- Mechanistic study of the palladium - Phenanthroline catalyzed carbonylation of nitroarenes and amines: Palladium - Carbonyl intermediates and bifunctional effects
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Palladium - phenanthroline complexes catalyze both the nitroarene carbonylation reaction and the amine oxidative carbonylation reaction to give, depending on the conditions, carbamates and ureas. There is evidence that the key step in both processes is the amine carbonylation. Here, we show that when the reaction is run in methanol key intermediate compounds have the general formula [Pd(RPhen)(COOMe)2] (1) (RPhen = l,10-phenanthroline or one of its substituted derivatives). The kinetics of the reaction of 1 with toluidine in the presence of a carboxylic or phosphorus acid is firstorder with respect to complex, acid, and toluidine. A CO atmosphere is also required for the reaction to proceed. Acid dimerization was shown not to be influential under the concentration conditions examined, but reaction between the acid and toluidine is not negligible and a correction has to be applied. Diphenylphosphinic acid is more effective than any carboxylic acid in promoting this reaction, as also observed under catalytic conditions. A series of equilibria and an irreversible acid-assisted proton transfer explain the observed data. Formation of an adduct between complexes of the kind 1 and CO was spectroscopically observed when RPhen = 2,9-Me2Phen. Several analogous complexes were also spectroscopically characterized and the X-ray structure of [Pd(2,9Me2Phen)Cl2(CO)] was solved. This shows an asymmetric coordination of the nitrogen ligand. Kinetic measurements were also conducted under catalytic conditions. An Eyring plot shows that the effect of the acidic promoter is to decrease the ?S * value, whereas no positive effect is observed on ?H*. A temperature-dependent correction for the reaction between the acid and aniline and phenanthroline present under the reaction conditions has to be applied. Comparison of the results obtained under stoichiometric and catalytic conditions strongly supports the view that 1 is involved even in the latter and that the acid is acting as a bifunctional promoter.
- Ragaini, Fabio,Gasperini, Michela,Cenini, Sergio,Arnera, Lucia,Caselli, Alessandro,Macchi, Piero,Casati, Nicola
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- Carbamate synthesis by solid-base catalyzed reaction of disubstituted ureas and carbonates
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A simple and efficient methodology to prepare carbamates has been demonstrated for the first time from symmetrical ureas and organic carbonates in the presence of solid base catalysts.
- Gupte,Shivarkar,Chaudhari
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- Phosphorus acids as highly efficient promoters for the palladium- phenanthroline catalyzed carbonylation of nitrobenzene to methyl phenylcarbamate
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A new family of promoters, based on phosphorus acids, is reported for the catalytic carbonylation of nitrobenzene to methyl phenylcarbamate by palladium-phenanthroline complexes. With the new promoters, unprecedented reaction rates (TOF up to 6000/h) and catalyst stability (TON up to 10 5) could be reached. The best promoter is phosphoric acid, which is also very cheap, nontoxic and easily separable from the reaction products.
- Ragaini, Fabio,Gasperini, Michela,Cenini, Sergio
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- Ruthenium Carbonyl Catalyzed Reductive Carbonylation of Aromatic Nitro Compounds. A Selective Route to Carbamates
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Ru3(CO)12 (1) and Ru(CO)3(PPh3)2 (2) catalyze the reductive carbonylation of nitrobenzene and of substituted aromatic mononitro compounds to give the corresponding methylcarbamates, in toluene-methanol, at 160-170 deg C and 60 atm, with high selectivity, in the presence of NEt4+Cl- as cocatalyst.Compound 1 also catalyzes the conversion of 2,4-dinitrotoluene into the corresponding dicarbamate although less efficiently.The effects of CO pressure, reaction temperature, and amount and nature of the added alcohol and cocatalyst have been studied.The mechanism of the reaction catalyzed by 1 has been investigated by studying the reactivity and catalytic activity of possible intermediates
- Cenini, Sergio,Crotti, Corrado,Pizzotti, Maddalena,Porta, Francesca
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- Mineral Oil/Methanol: A Cheap Biphasic Reaction Medium with Thermomorphic Properties and Its Application to the Palladium-Catalyzed Carbonylation of Nitrobenzene to Methyl Phenylcarbamate
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We developed the methanol/mineral oil system as a new thermomorphic solvent mixture that allows homogeneous catalyst recovery without the use of water or fluorinated solvents. Mineral oil (nujol) is cheap and shows a very limited miscibility with methanol at room temperature but becomes completely miscible at high temperatures. Here we report the synthesis of some phenanthrolines substituted with long-chain alkyl groups, which render them soluble in hydrocarbons and insoluble in methanol, and their application to the palladium-catalyzed carbonylation of nitrobenzene to methyl phenylcarbamate. Both the reagents and products of the catalytic reaction are much more soluble in methanol than in hydrocarbons, so an easy separation of the catalyst is possible.
- Ferretti, Francesco,Gallo, Emma,Ragaini, Fabio
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- Efficient and recyclable heterogeneous zinc alkyl carboxylate catalyst for the synthesis of N-phenyl carbamate from aniline and dimethylcarbonate
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Zinc alkyl carboxylate molecules were chemically bonded on a silica surface through an elaborately designed precursor agent and special grafting method. The heterogeneous salt catalyst possessing a cyclic single active site was highly active and recyclable in the reaction between dimethylcarbonate and aniline to produce methyl N-phenyl carbamate.
- Wang, Yi,Liu, Bo
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- CANNABINOID DERIVATIVES
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This disclosure relates generally to cannabinoid derivatives, pharmaceutical compositions comprising them, and methods of using the cannabinoid derivatives.
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Paragraph 0154
(2021/06/22)
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- Lossen rearrangement by Rh(iii)-catalyzed C-H activation/annulation of aryl hydroxamates with alkynes: Access to quinolone-containing amino acid derivatives
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A convenient and robust method for the preparation of new CF3-containing 2-quinolones has been developed via a Rh(iii)-catalyzed C-H activation/Lossen rearrangement/annulation cascade of N-pivaloyloxy-arylamides with internal alkynes bearing an α-CF3-α-amino acid moiety on the triple bond. This work expands the scope of valuable products that are available through C-H activation/annulation reactions of arylamides in organic synthesis. This journal is
- Petropavlovskikh, Dmitry A.,Vorobyeva, Daria V.,Godovikov, Ivan A.,Nefedov, Sergey E.,Filippov, Oleg A.,Osipov, Sergey N.
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supporting information
p. 9421 - 9426
(2021/11/17)
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- A convenient Hofmann reaction of carboxamides and cyclic imides mediated by trihaloisocyanuric acids
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A simple, efficient and pot-economic approach in a single vessel has been developed for conversion of aromatic and aliphatic carboxamides into primary amines with one fewer carbom atom (Hofmann reaction) in 38–89 % yield by reacting with trichloro- or tribromoisocyanuric acid and sodium hydroxide in aqueous acetonitrile. Under the same reaction conditions, cyclic imides gave amino acids (69–83 %). The role of the trihaloisocyanuric acids is the in situ generation of N-haloamides, key-intermediates for the Hofmann reaction. The scalability of the methodology was demonstrated by a multigram-scale transformation of phthalimide into anthranilic acid in 77 % yield.
- Bastos, Gustavo A.,de Mattos, Marcio C.S.
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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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- 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 0014-0022
(2021/08/13)
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- ZINC-IMIDAZOLE COMPLEX MIXED CATALYST AND METHOD FOR PRODUCING METHYL N-PHENYL CARBAMATE USING THE SAME
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Disclosed is a zinc-imidazole complex mixed catalyst. Also disclosed are a method for preparing the zinc-imidazole complex mixed catalyst and a method for producing a methyl N-phenyl carbamate in high yield with high selectivity in the presence of the catalyst. The zinc-imidazole complex mixed catalyst can be reused due to its high reaction stability. In addition, the use of the zinc-imidazole complex mixed catalyst leads to a marked improvement in the production yield of a methyl N-phenyl carbamate with high selectivity.
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Paragraph 0077-0078; 0089-0090
(2020/03/09)
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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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- 2-((disubstituted sulfonyl)methylene)-N-arylhydrazino-1-formamide derivative and preparation method and application thereof
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The invention discloses a 2-((disubstituted sulfonyl)methylene)-N-arylhydrazino-1-formamide derivative and a preparation method and application thereof. In the structural general formula (I), R1 is asubstituent such as a hydrogen atom, 4-chlorphenyl, 4-fluorophenyl, 3-methylphenyl, 3, 5-xylyl, 2, 6-xylyl and the like, and R2 is substituent groups such as methyl, ethyl, propyl, isopropyl, benzyl and 4-methyl benzyl. The compound has excellent antibacterial activity in bacterial diseases such as bacterial blight of rice, bacterial streak of rice, bacterial wilt of tobacco, bacterial leaf spot of pepper, citrus canker and the like, and is simple in structure and relatively stable in compound property.
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Paragraph 0059-0062; 0071-0073; 0076-0078; 0081-0083
(2020/11/01)
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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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- 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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- Methyl N -phenyl carbamate synthesis over Zn/Al/Ce mixed oxide derived from hydrotalcite-like precursors
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Methyl N-phenyl carbamate (MPC) is an important intermediate for the green synthesis of methylene diphenyl diisocyanate (MDI) as well as many other important products. In the present work, Zn/Al/Ce mixed oxides derived from hydrotalcite-like precursors were employed as effective and recoverable heterogeneous catalyst for MPC synthesis via DMC aminolysis. Zn/Al/Ce hydrotalcite-like precursors prepared via coprecipitation method and the resulting catalysts were characterized by means of XRD, BET, SEM and XPS. Strong interactions within the Zn/Al/Ce mixed oxides were observed via the addition of appropriate amount of cerium. The mixed oxides containing 2.5% cerium showed high DMC aminolysis activity giving aniline conversion of 95.8%, MPC selectivity of 81.6% and MPC yield of 78.2%. Moreover, as a heterogeneous catalyst, it also exhibited superiorities of easy recovery and recyclable stability for MPC synthesis.
- Kang, Min,Zhou, Hai,Tang, Dajiang,Chen, Xiaomei,Guo, Ying,Zhao, Ning
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p. 42474 - 42480
(2020/01/08)
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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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- 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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- Formation of defect site on ZIF-7 and its effect on the methoxycarbonylation of aniline with dimethyl carbonate
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The Zeolitic Imidazole Framework ZIF-7, (Zn(benzimidazole)2), is known to exhibit a unique gate-opening property depending on the temperature and pressure in the presence of guest molecules, making it useful for H2, CO2, and paraffine separation technology. Besides this distinctive gas adsorption property, ZIF-7 can be used as a catalyst because it contains a Lewis acid site on Zn, and a Lewis basic site on the benzimidazole. In this study, for the first time, we demonstrate that ZIF-7 is a very promising material as a catalyst for the methoxycarbonylation of aniline with dimethyl carbonate (DMC) to produce methyl phenyl carbamate (MPC), an isocyanate precursor. Fresh ZIF-7 showed a high aniline conversion of over 95% at 190 °C for 2 h, and the yield MPC was 60–70% due to the formation of methylated side products, such as N-methyl aniline and N,N′-dimethylaniline. However, interestingly, when the ZIF-7 was reused, the yield of MPC gradually increased and reached over 94.7% by the catalyst's 6th run. SEM and TEM images revealed the crystalline structure of ZIF-7 collapsed during the reaction due to the leaching of benzimidazole from the ZIF-7, which created defect sites on the Lewis acidic zinc center. Based on 1H NMR and XPS studies, it can be assumed that the DMC binds to the Zn defect sites on the ZIF-7, activating the carbonyl groups on DMC, resulting in the increased selectivity to methoxycarbonylation compared to methylation. Pretreating ZIF-7 with DMC at 190 °C for 6 h could directly activated the ZIF-7 for this methoxycarbonylation reaction. The activated ZIF-7 showed 91.0% MPC yield and the catalyst was reusable.
- Dahnum, Deliana,Seo, Bora,Cheong, Seok-Hyeon,Lee, Ung,Ha, Jeong-Myeong,Lee, Hyunjoo
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p. 297 - 306
(2019/11/03)
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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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- Synthesis, characterisation, and reactivity of novel pseudocyclic hypervalent iodine reagents with heteroaryl carbonyl substituents
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Two new hypervalent iodine reagents containing furan and thiophene moieties in addition to a carbonyl group in the vicinity of the iodine atom were synthesised and characterised. The X-ray analysis of both compounds revealed a strong intramolecular contact between the carbonyl oxygen and the hypervalent iodine atom with tosylate as a counter ion. The two reagents showed a broad range of synthetic applications and proved to be versatile oxidizing agents.
- Qurban, Jihan,Elsherbini, Mohamed,Alharbi, Haifa,Wirth, Thomas
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supporting information
p. 7998 - 8000
(2019/07/12)
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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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- 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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- Sulfonyl-containing thioformylhydrazine derivatives, preparation method and application thereof
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The invention discloses sulfonyl-containing thioformylhydrazine derivatives, a preparation method and application thereof. A structural general formula (I) of the sulfonyl-containing thioformylhydrazine derivatives is as follows, wherein R1 is methyl, ethyl, benzyl, 4-methyl benzyl or 2,4-dichlorobenzyl; R2 is hydrogen atom, 4-chlorine, 4-fluoride, 3-methyl, 3,5-dimethyl or 2,6-dimethyl. The sulfonyl-containing thioformylhydrazine derivatives have excellent resistance to bacterial diseases such as rice bacterial leaf blight bacteria, rice bacterial streak bacteria, citrus canker bacteria and the like, and are simple in structure and relatively stable in compound properties. (Shown in the description).
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Paragraph 0054; 0055; 0056
(2019/05/22)
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- N-substituent group-N-(substituted phenylaminocarbonyl)-1-substituted sulfonylthioformylhydrazide derivatives and application thereof
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The invention discloses N-substituent group-N-(substituted phenylaminocarbonyl)-1-substituted sulfonylthioformylhydrazide derivatives as well as a preparation method and application thereof. The derivatives have a structural general formula (I) shown in the description, wherein n = 0, 1 or 2, and X = C, N, O or S; R1 is C1-4 alkyl or substituted benzyl; and R2 is a hydrogen atom, an o-position, anm-position, a p-position monosubstituted halogen atom, C1-4 alkyl, C1-2 alkoxy, or a polysubstituted halogen atom. The derivatives provided by the invention have excellent antibacterial activity against bacterial diseases such as xanthomonas oryzae, xanthomonas oryzicola and xanthomonas citri, the synthetic raw materials have low costs, and the synthetic method is simple and easy.
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Paragraph 0042-0044
(2019/11/28)
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- PRODUCTION OF N-SUBSTITUTED AROMATIC HYDROXYLAMINE
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An economic, one-step method for the production of N-substituted aromatic hydroxylamines of formula (I) [in-line-formulae]R—N(OH)—C(═O)—(O)R1??(I),[/in-line-formulae] with hydrogen, by catalytic hydration with possibly modified hydration catalysts in an aprotic solvent and in the presence of a halogen formic acid ester and in some cases in the presence of a base.
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Paragraph 0047-0048
(2020/01/12)
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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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- 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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- 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 0031-0049
(2019/07/03)
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- A PROCESS FOR THE SYNTHESIS OF AROMATIC CARBAMATES
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The present invention discloses a process for the synthesis of aromatic carbamates from amine with dialkyl carbonate in the presence of binary or ternary mixed metal oxide catalyst. The present invention further discloses the yield of said aromatic carbamate in the range of 60 to 99%. Further, the ratio of amine to dialkyl carbonate is in the range of 1:2 to 1:30.
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Page/Page column 13; 16
(2018/12/13)
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- SILICA-BASED ZINC CATALYSTS. THEIR PREPARATION AND USE IN THE ALKOXYCARBONYLATION OF AMINES
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The present invention relates to silica-based heterogeneous zinc compounds which are suitable as catalysts in the reaction of amines with dialkyl carbonates to produce carbamates. The catalysts have the formula [SiO2]-CH2-CHR-X-COOZn[Y], wherein [SiO2] represents a silica carrier selected from the group consisting of ordered mesoporous silica and irregular amorphous narrow pore silica, R represents a moiety selected from the group consisting of hydrogen, -CH3, and -CH2CH3, preferably hydrogen, X is an aliphatic chain of 2 to 11 carbon atoms that optionally comprises ether moieties and [Y] represents a mono anion. The invention is also directed towards a method for the preparation of the aforementioned compounds and towards method for the alkoxycarbonylation of amines.
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Page/Page column 22-28
(2018/12/13)
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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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- Spontaneous and direct transformation of N,O-diaryl carbamates into N,N′-diarylureas
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We have discovered a spontaneous reaction of N,O-diaryl carbamates to afford symmetrical N,N′-diarylureas. Optimization of the conditions indicated that N,N-dimethylformamide (DMF) was the best solvent and triethylamine (Et3N) was the best additive for this transformation. The reaction requires the presence of aryl groups on the nitrogen and oxygen atoms of carbamates. Substrates bearing an electron-donating methoxy group on either of the aryl groups reacted slowly under these conditions.
- Yamasaki, Ryu,Honjo, Yutaka,Ito, Ai,Fukuda, Kazuo,Okamoto, Iwao
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p. 880 - 884
(2018/09/10)
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- NOVEL CYCLIC UREA DERIVATIVE-HYDROTRIBROMIDE
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PROBLEM TO BE SOLVED: To provide a novel bromination agent easy to handle. SOLUTION: There are provided a compound represented by a general formula (1) where n is 1 or 2, R1 and R2 may be same or different and represent an alkyl group having 1 to 4 carbon atoms, preferably a methyl group, and a bromination agent using the same. EFFECT: A cyclic urea derivative-hydrotribromide, which can be used as the bromination agent, can be provided, and the compound can be applied to various bromination reactions because it is stable solid and is easy to handle. SELECTED DRAWING: None COPYRIGHT: (C)2019,JPOandINPIT
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Paragraph 0042; 0043; 0044
(2018/11/22)
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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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- 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
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Paragraph 0041; 0043
(2018/10/16)
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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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- Metal-Free Synthesis of Unsymmetrical Ureas and Carbamates from CO2 and Amines via Isocyanate Intermediates
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A mild and metal-free synthesis of aryl isocyanates from arylamines under an atmosphere of CO2 was developed. The carbamic acid intermediate, derived from the arylamine starting material and CO2 in the presence of DBU, is dehydrated by activated sulfonium reagents to generate the corresponding isocyanate. The latter can be detected by in situ IR and trapped by various amines and alcohols to make unsymmetrical ureas and carbamates, respectively. Dicarbamates can also be prepared in good yields via the mild dehydration of the corresponding dicarbamic acids.
- Ren, Yiming,Rousseaux, Sophie A. L.
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p. 913 - 920
(2018/01/28)
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- Synthesis process of 4, 4'-methylene diphenyl dicarbamate
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The invention discloses a synthesis process of 4, 4'-methylene diphenyl dicarbamate (MDC). Aniline, dimethyl carbonate and formaldehyde are adopted as the raw materials, and MPC synthesis and MDC synthesis reactions are continuous. The invention solves the defects of batch operation and complex process in the prior art employing dimethyl carbonate to prepare methylene diphenyl dicarbamate. The method includes: adding aniline, dimethyl carbonate and a zinc ion catalyst into a reactor in order to carry out reaction at 120-200DEG C for 1-10h, cooling the reaction liquid to 60-100DEG C, adding concentrated hydrochloric acid, and adding a formaldehyde aqueous solution, then carrying out reaction at 60-100DEG C for 10-200min, distilling the reaction solution to remove the solvent, and carrying out filtering, separation and recrystallization to obtain 4, 4'-methylene diphenyl dicarbamate. The overall yield is up to 67%.
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Paragraph 0013
(2017/09/08)
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- Zinc-amine complex catalyst, preparation method therof and preparation method for methyl N-phenyl carbamate using the same
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The present invention relates to a zinc-base complex catalyst for synthesizing N-methyl aryl carbamate from an aromatic amine and dimethyl carbonate and a preparation method of N-methyl aryl carbamate using the catalyst. More specifically, the present invention relates to a zinc-base complex catalyst which is used in preparing N-methyl aryl carbamate from the aromatic amine and dimethyl carbonate, and which is prepared by synthesizing a zinc salt having characteristics of Lewis acid and a base having basic properties into a complex, and a preparation method of N-methyl aryl carbamate using the catalyst. A zinc-amine complex of the present invention comprises zinc and amine, wherein the zinc and amine have a mole ratio of 1:1 to 5, and the amine is one or more tertiary amines selected from the group consisting of chemical formulas 1 to 6. In chemical formulas 1 to 6, R_1, R_2, R_3 and R_4 are each equal to or different from one another, and are each independently an alkyl group having 1 to 6 carbon atoms. The zinc-base complex catalyst of the present invention comprises the zinc-amine complex. The zinc-base complex catalyst according to the present invention provides a synthesis process which can obtain N-methyl aryl carbamate at a high yield, has a very high selectivity, and environmentally friendly since the zinc-base complex catalyst has excellent reactivity when applying the zinc-base complex catalyst to the synthesis of N-methyl aryl carbamate from the aromatic amine and dimethyl carbonate.COPYRIGHT KIPO 2017
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Paragraph 0110; 0121; 0123
(2018/02/20)
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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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- Direct preparing method of carbamate compounds from amines
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The present invention relates to a direct preparation method of a carbamate compound from an amine compound, and more particularly, to direct preparation method of a carbamate compound by reacting the amine compound and an alcohol compound, in a mixed gas atmosphere of carbon monoxide (CO) and oxygen (O_2), by using a Pd/HY-zeolite catalyst carrying a palladium (Pd) active metal, in a HY-zeolite carrier having a controlled molar ratio of SiO_2/Al_2O_3.COPYRIGHT KIPO 2017
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Paragraph 0044-0047; 0060
(2017/08/26)
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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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- Base-Catalyzed Transcarbamoylation
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Inorganic bases such as NaH, KO t -Bu, NaOH, or KOH are efficient catalysts to promote the transcarbamoylation reaction between urethanes and a variety of primary and secondary alcohols under mild conditions. They constitute an alternative to organometallic catalysis and can be applied to aliphatic or aromatic urethanes.
- Rhoné, Beno?t,Semetey, Vincent
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supporting information
p. 2004 - 2007
(2017/09/13)
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- Method for preparing methyl carbamate by catalyzing methanol conversion
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The invention discloses a method for preparing methyl carbamate by catalyzing methanol conversion. The method specifically comprises: taking oxygen or air as an oxygen source, taking organic amine as a nitrogen source, taking methanol as a solvent, in the function of a catalyst, allowing methanol to undergo ammoxidation to generate methanamide, and allowing methanamide to undergo in-situ oxidation esterification to obtain methyl carbamate. The method is high in raw material utilization rate. The catalyst is cheap and available, is easy to recycle, can be reused, and is easy to separate from the product. The obtained methyl carbamate is excellent in performance and high in purity. The technical route is of great significance in releasing excess production capacity of methanol and reducing the dependence on highly toxic chemicals.
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Paragraph 0029; 0042-0044
(2018/01/09)
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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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- 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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p. 1297 - 1300
(2017/06/23)
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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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- 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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- Hofmann Rearrangement of Carboxamides Mediated by N-Bromoacetamide
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An efficient, one-pot procedure for the Hofmann rearrangement of aromatic and aliphatic amides has been developed. Methyl and benzyl carbamates are produced with N-bromoacetamide in the presence of lithium hydroxide or lithium methoxide, in high yields. β-Phenylamino amides gave five-membered cyclic ureas stereospecifically. Side products of aryl or benzyl bromination were minimized. This procedure offers an easy access to various protected amines or diamines, which represent important synthetic precursors.
- Jevti?, Ivana I.,Do?en-Mi?ovi?, Ljiljana,Ivanovi?, Evica R.,Ivanovi?, Milovan D.
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p. 1550 - 1560
(2016/06/01)
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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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- One-pot synthesis of carbamates and thiocarbamates from Boc-protected amines
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A highly efficient one-pot procedure for the synthesis of carbamates and thiocarbamates has been described. In the presence of 2-chloropyridine and trifluoromethanesulfonyl anhydride, the isocyanate intermediates were generated in situ for further reactions with alcohols and thiols to afford the desired carbamates and thiocarbamates in high yields.
- Kim, Hee-Kwon,Lee, Anna
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supporting information
p. 4890 - 4892
(2016/10/21)
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