- Catalytic synthesis of methylene diphenyl dicarbamate from methyl phenyl carbamate and trioxane over sulfuric acid catalyst
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Methylene diphenyl dicarbamate (MDC) was synthesized from methyl phenyl carbamate (MPC) and trioxane using sulfuric acid (H2SO4) as catalyst. The effects of reaction temperature, reaction time, molar ratio of reactants and the content of catalyst have been studied in details. The results showed that H2SO4 exhibited high catalytic activity with the merits of moderate reaction velocity. Under the conditions of n(MPC)/n(trioxane) = 3:1, reaction temperature of 95°C, reaction time of 3.5 h and 30% H2SO4, the conversion of MPC reached 99.0% with the selectivity of MDC 81.6%. Moreover, the H2SO4 catalyst was reused five times without obviously activity decrease. Based on the identification of byproducts, a possible reaction mechanism was proposed. Higher Education Press and Springer-Verlag Berlin Heidelberg 2010.
- Li, Tao,Li, Huiquan,Qin, Guotong,Liu, Haitao,Pei, Yixia
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Read Online
- The method for preparing dicarbamate compounds from diamines and the catalyst thereof
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The present invention relates to a method of directly preparing a dicarbamate compound from a diamine compound, and more particularly to a method of directly preparing a dicarbamate compound by reacting a diamine compound with an alcohol compound in the presence of a mixed gas of carbon monoxide (CO) and oxygen (O2) using a Pd/MOx catalyst configured such that a palladium (Pd) active metal is supported on a metal oxide or metalloid oxide carrier.
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Paragraph 0083-0085
(2022/01/12)
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- Montmorillonite K30 Supported Tungstophosphoric Acid as an Efficient Catalyst for Condensation Reaction of Methyl N-phenylcarbamate for Generating Diurethane
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Methylene diphenyl-4,4′-dicarbamate (MDC) was prepared via condensation reaction of methyl N-phenyl carbamate (MPC) and formaldehyde (HCHO) over montmorillonite K30 supported tungstophosphoric acid (TPA/K30) as an effective catalyst. A 26.2?wt.% TPA/K30 exhibited the highest product yield (75.5%) under a mild reaction temperature of 90?°C for 4?h at the molar ratio of MPC/HCHO = 4. Pyridine FTIR study indicates that Br?nsted and Lewis acid sites in the TPA/K30 were found to be beneficial for achieving an excellent yield of MDC. Furthermore, the TPA/K30 could be reused at least four runs without significant loss in the original activity. Graphic Abstract: [Figure not available: see fulltext.].
- Baek, Jayeon,Baik, Joon Hyun,Kim, Yong Jin,Lee, Hye Jin,Tran, Anh Vy
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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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- A green route to polyurethanes: Oxidative carbonylation of industrially relevant aromatic diamines by CO2-based methyl formate
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The oxidative carbonylation of toluene-2,4-diamine (TDA) with methyl formate (MF), which can be produced from CO2, provides a possible route for the non-phosgene production of isocyanate precursors and enables a valuable utilization of the greenhouse gas. Extensive analysis of the product spectrum has provided detailed insight into the reaction network leading to the target product toluene-2,4-dicarbamate (TDC) and the most important side products. The most prominent one has been identified as methylene-bridged tetracarbamate 5, which is also an interesting precursor for applications in polyurethane chemistry. The side products are caused by three different reaction paths: N-formylation by MF, condensation with in situ formed formaldehyde, and N-methylation by in situ formed dimethyl carbonate (DMC). The influence of the catalyst on product distribution was evaluated for PdCl2/CuCl2 and a large number of heterogeneous Pd-catalysts. The oxidic support materials ZrO2, CeO2 and SiO2 were found to partially suppress the undesired side reactions leading to higher yields of TDC and tetracarbamate 5. The ratio of TDC to 5 was demonstrated to be affected significantly by the choice of the support. The synthetic protocol was extended to the synthesis of dicarbamates from 4,4′-methylenedianiline (MDA) and 2,4-diaminomesitylene (17). These results encourage further investigations into the design of selective catalysts for the production of isocyanate precursors from CO2 as a C1 source.
- Hussong, Christine,Langanke, Jens,Leitner, Walter
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supporting information
p. 8260 - 8270
(2020/12/31)
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- Synthesis, antimicrobial and antioxidant activity of bis sulfonamide/carbamate derivatives of bis-(4-aminophenyl) methane
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A series of new bis sulfonamide/carbamate derivatives of bis-(4-aminophenyl)methane 3(a–d)/5(a–f) were synthesized from bis-(4-aminophenyl)methane (1) using various pharmacologically active sulfonyl chlorides 2(a–d) and carbonochloridates 4(a–f) in high yields. The structures of all the newly synthesized compounds were characterized by the Infrared spectroscopy, NMR (1H and 13C), mass, and elemental analyses. Further, all the synthesized compounds were tested for the antioxidant activity by using 2, 2-diphenyl-1-picrylhydrazyl, NO, and H2O2 scavenging methods and antimicrobial activity. Most of the compounds exhibited good antioxidant and antimicrobial activities.
- Nagalakshmamma, Vadabingi,Varalakshmi, Mavallur,Umapriya, Kollu,Venkataswamy, Mallepogu,Venkataramaiah, Chintha,Thyaga Raju, Kedam,Chalapathi, Ponne Venkata,NagaRaju, Chamarthi
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p. 1289 - 1295
(2020/02/11)
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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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- METHOD FOR PREPARING METHYLENE DIPHENYL-4,4'-DICARBAMATE DERIVATIVE BY CONDENSATION REACTION OF URETHANE
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The present invention relates to a method for manufacturing a methylene diphenyl-4,4andprime;-dicarbamate derivative which comprises a step of manufacturing the methylene diphenyl-4,4andprime;-dicarbamate derivative by conducting a condensation reaction of a N-phenyl carbamate derivative and formaldehyde by using clay carrying heteropoly acid as a catalyst. By the same, it is possible to manufacture the methylene diphenyl-4,4andprime;-dicarbamate derivative which is eco-friendly by not using a toxic reactant, and has a high yield.COPYRIGHT KIPO 2020
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Paragraph 0092-0203
(2020/07/29)
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- Zr-MOF-808@MCM-41 catalyzed phosgene-free synthesis of polyurethane precursors
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In this work, a catalytic method is presented for the synthesis of aromatic carbamates from aromatic amines using dimethyl carbonate instead of phosgene as a green and safe reaction process. Microcrystalline Zr-MOF-808 is reported as an active and efficient heterogeneous catalyst for the selective carbamoylation of anilines and industrially relevant aromatic diamines, under mild reaction conditions with near quantitative yields. We have accomplished the selective growth of well-dispersed Zr-MOF-808 nanocrystals within the mesoporous material MCM-41. A superior catalytic performance of the Zr-MOF-808@MCM-41 is demonstrated that together with increased stability stands out as an advantageous heterogeneous catalyst for polyurethane production. In situ FTIR studies have allowed a better understanding of the reaction pathway at the molecular level when the active MOF catalyst is present.
- Rojas-Buzo, Sergio,García-García, Pilar,Corma, Avelino
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p. 146 - 156
(2019/01/10)
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- PRODUCTION METHOD OF CARBAMIC ACID ESTER
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A method of production of carbamic acid ester has a high yield and high selectivity and is superior in economy. The method of production of a carbamic acid ester includes reacting an amine, carbon dioxide, and an alkoxysilane compound in the presence of a catalyst containing a zinc compound or an alkali metal compound or in the presence of an ionic liquid. A carbamic acid ester is produced, for example by reacting aniline, carbon dioxide, and tetramethoxysilane at a temperature of 150 to 180° C. in the presence of zinc acetate and 2,2′-bipyridine.
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Paragraph 0048; 0051
(2019/07/03)
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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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- 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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- 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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- Ionic liquid-mediated solvothermal synthesis of 4,4′-methylenediphenyl diisocyanate (MDI): An efficient and environment-friendly process
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4,4′-Methylenediphenyl diisocyanate (4,4′-MDI) is an immensely important intermediate employed in the manufacturing of polyurethanes. Many synthetic routes have been developed over the decades for the synthesis of 4,4′-MDI compounds on a large scale; these compounds are highly toxic and hazardous in nature. In this study, an environment-friendly route is proposed for the synthesis of 4,4′-MDI using 4,4′-diaminodiphenylmethane and dimethyl carbonate (DMC) as starting materials, which are nontoxic in nature. The synthesis of ionic liquids (ILs) and their utilization in the decomposition reaction are systematically investigated. Imidazole-functionalized ionic liquids were prepared for the synthesis of 4,4′-MDI, and their thermal performances were evaluated by TGA. We found that in comparison with other imidazole-functionalized ionic liquids, 1-ethoxycarbonylmethyl-3-methylimidazolium tetrafluoroborate ([EAmim]BF4) exhibited preferable thermal activity for the decomposition of 4,4′-methylenediphenyl dimethylcarbamate (4,4′-MDC). Moreover, these ILs were more effective when they were combined with zinc as a catalyst, which enhanced the decomposition of MDC. Under optimal conditions, the yield of MDI compared to that of Zn(OAc)2-[EAmim]BF4 catalyst increased up to 96%. The mechanism of the enhanced performance of ionic liquids by catalytic activity of zinc acetate was also investigated.
- Duan,You,Liu,Ma,Zhou,Zhang,Zhang
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p. 12243 - 12255
(2018/07/24)
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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 15
(2018/12/13)
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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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- Method for continuous catalytic preparation of 4, 4 '-methylene diphenyl dicarbamate
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A method for continuous catalytic preparation of 4, 4 '-methylene diphenyl dicarbamate is disclosed, and the methylene diphenyl dicarbamate is prepared from methyl phenyl carbamate (MPC) and formaldehyde as raw materials in the presence of an organic solvent by successive condensation under the condition of catalysis of a supported heteropoly solid acid catalyst. The method solves the defects of intermittent operation, equipment corrosion, environmental pollution, low conversion rate and low selectivity and the like in the prior art. The MDC conversion rate of the method is more than 99%, and the selectivity is greater than 81.6%.
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Paragraph 0023
(2017/06/20)
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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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- 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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p. 1478 - 1484
(2017/08/29)
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- PROCESS FOR PREPARING ISOCYANATE COMPOUND
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The present invention relates to a process for the preparation of an isocyanate compound comprising the steps of: a) Reacting an amine compound A having at least one primary amino group with CO2 and an organotin compound S having at least one radical OR3 attached to the tin atom of the organotin compound, wherein R3 is a C-bound organic radical having from 1 to 30 carbon atoms, wherein 1, 2 or 3 carbon atoms may be replaced by oxygen or nitrogen, to convert at least one of the primary amino groups in the amine compound A into a carbamate group, thereby obtaining a carbamate compound C; b) cleavage of the carbamate groups in the carbamate compound C obtained in step a) to form the isocyanate compound and an alcohol R3OH, without separation of the tin compound formed in step a); c) obtaining the isocyanate compound from the reaction mixture of step b).
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Page/Page column 20; 21
(2016/11/21)
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- ZINC CLUSTER COMPOUNDS AND THEIR USE AS CATALYSTS IN THE REACTION OF AMINES WITH DIALKYL CARBONATES
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The present invention relates to metallic zinc cluster compounds which are suitable as catalysts in the reaction of amines with dialkyl carbonates to produce carbamates. The invention is also directed towards a method for the alkoxycarbonylation of amines. The cluster compound has a general formula which may be written as [M(O2C-R)2]x- [MO]y- [H2O]z, wherein M is Zn, R is an unsubstituted or substituted aromatic, cycloaliphatic, linear aliphatic, or other organic rest, x is 1, y is > x is 1, y is > 0.03 to 0.00 to 17.0.
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Page/Page column 12
(2014/12/12)
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- Process for preparing aromatic carbamates
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The invention is directed to a process for preparing aromatic carbamates which comprises the reaction of an aromatic amine with an organic carbonate in the presence of a catalyst characterized in that Zn4O(OAc)6 is used as catalyst.
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Page/Page column 9; 10
(2010/10/03)
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- PROCESS FOR PRODUCING ISOCYANATE
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An object of the present invention is to provide a process allowing long-term, stable production of isocyanates at a high yield without the various problems found in the prior art during production of isocyanates without using phosgene. The present invention discloses a process for producing an isocyanate by subjecting a carbamic acid ester to a decomposition reaction in the presence of a compound having an active proton and a carbonic acid derivative.
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Page/Page column 53
(2009/09/05)
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- Novel material forming supramolecular structures, process and uses
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The invention relates to novel material, forming supramolecular structures below its transition temperature, which contains at least one C=O and/or C=S group and at least one N—H, O—H and/or S—H group and wherein the material has the structure [in-line-formulae]A(—X—B)n ??(1)[/in-line-formulae] wherein A is a cyclic, aromatic and/or aliphatic group, n being a number of 1 to 4, —X—B is, if n is 2, the same or different, and if n is 3 or 4, the same, partly the same or different and has one of the structures (2) to (4) [in-line-formulae]NH—C(Y)—Y—B ??(2)[/in-line-formulae] [in-line-formulae]—NH—C(Y)—NR—B ??(3)[/in-line-formulae] [in-line-formulae]—Y—C(Y)—NR—B ??(4)[/in-line-formulae] with Y being an Oxygen and/or Sulfur atom, B being an organic group with at least one heteroatom, where the heteroatom is bound to at least two carbon atoms when B is linear or cyclic, and where the heteroatom is bound to at least one carbon atom when B is branched, and R being a Hydrogen atom, a cyclic, aromatic and/or aliphatic group or another B group which is the same or different. The material can be made by reacting at least one isocyanate and/or thioisocyanate with at least one amine, alcohol and/or thiol. Typically, the material is used first below its transition temperature, followed by increasing the temperature to around or above the transition temperature, carrying out a process step and subsequently decrease the temperature below the transition temperature.
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Page/Page column 10;12
(2008/12/08)
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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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- Carbomethoxylating reactivity of methyl phenyl carbonate toward aromatic amines in the presence of group 3 metal (Sc, La) triflate catalysts
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Methyl phenyl carbonate (MPC) has been investigated as a carbomethoxylating agent of aromatic amines in the presence of group 3 metal (Sc or La) triflate catalysts. Under mild conditions (363 K), both Sc(OTf)3 and La(OTf)3 (OTf=O3SCF3) can promote the carbamation of aniline and a few industrially relevant aromatic diamines, such as 4,4′-methylenedianiline (MDA) and 2,4-diaminotoluene (TDA), with MPC. Carbamate yield and selectivity are markedly affected by the experimental conditions (temperature, reaction medium, nature of the metal center). Sc(OTf)3 is a more effective and selective carbamation catalyst than La(OTf)3 . Ad hoc experiments have shown that, in the presence of the M(OTf)3 (M=Sc, La) catalysts, MPC is not only more reactive but also a more selective carbomethoxylating agent than dimethyl carbonate (DMC).
- Distaso, Monica,Quaranta, Eugenio
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- First gold(I) complex-catalyzed oxidative carbonylation of amines for the syntheses of carbamates
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At 200 °C and 5 MPa of initial total pressure, the oxidative carbonylation of amines for the synthesis of the corresponding carbamates by Au(I) complexes as catalysts was conducted with excellent conversion and selectivity.
- Shi,Deng
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p. 443 - 444
(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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- NEW PHOSGENE-FREE PROCEDURE FOR PREPARATION OF METHYL N-PHENYLCARBAMATE AND DIMETHYL DIPHENYLMETHANE DICARBAMATE AS IMPORTANT PRECURSORS FOR PRODUCING ISO- AND DIISOCYANATES
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Methyl N-phenylcarbamate was prepared by reductive carbonylation of nitrobenzene in the presence of methanol and a new catalytic system composed of sulfur, vanadium pentoxide and a base - alkoxides of alkali metals or hydroxides of alkali metals or alkali earths - in good yields.Reaction mechanism of this process is discissed.Diphenylmethane dicarbamates were obtained by acid-catalyzed condensation of methyl N-phenylcarbamate with formaldehyde.Concentrated and dilute sulfuric acids, dilute hydrochloric acid, a mixture of hydrochloric and sulfuric acids, and bentonite were the catalysts investigated.The influence of the catalyst used, the molar ratio of methyl N-phenylcarbamate (MPC) to formaldehyde, temperature and reaction time of yields of dimethyl 4,4'-diphenylmethane dicarbamate and its higher homologues was examined.The condensation products were analysed by high-performance liquid chromatigraphy on reversed phases (RP-HPLC) with a favourable chemically bonded octadecyl stationary phase and a mixed mobile phase water-methanol.
- Jakus, Vladimir,Bojsova, Eva
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p. 1505 - 1515
(2007/10/02)
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- A New Method for a Kinetic Study of Reactions between Di-isocyanates and Alcohols. Part 1. Symmetrical Di-isocyanates
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A new method of following the kinetics of the uncatalysed reaction between di-isocyanates and alcohols, which allows the determination of the concentration of all the species occurring during the reaction, by means of the high performance liquid chromatography (HPLC), is described.It has been found that the relationship between the unchanged fraction and the fraction that reacts, theoretically inferred for ideal systems (null catalytic effects), is validated over the whole reaction for real systems.This fact is a verification that the reduced time, τ, is a result of the total catalytic effects, and is a surprising simplification of the kinetics of this type of complex process.The following value ratios of the rate constant (R) for the first and the second NCO groups for various di-isocyanates were determined: 4,4'-BDI R = 1.36, 4,4'-BBDI R = 1.30, p-PDI R = 2.57, m-PDI R = 3.07.
- Caraculacu, Adrian A.,Agherghinei, Ion,Gaspar, Mariana,Prisacariu, Cristina
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p. 1343 - 1348
(2007/10/02)
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- HYDROGENATION OF N-ARYL CARBAMATES TO N-ALICYCLIC CARBAMATES.
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An economical, high-yield process is developed for the preparation of pure N-alicyclic carbamates by the rhodium-catalyzed hydrogenation of the corresponding N-aryl carbamates. The N-aryl carbamates are obtained by the simple reaction of low-cost aromatic
- Malz Jr.,Greenfield
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p. 358 - 362
(2007/10/06)
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