- Dehydrogenative Synthesis of Carbamates from Formamides and Alcohols Using a Pincer-Supported Iron Catalyst
-
We report that the pincer-ligated iron complex (iPrPNP)Fe(H)(CO) [1, iPrPNP- = N(CH2CH2PiPr2)2-] is an active catalyst for the dehydrogenative synthesis of N-alkyl- and N-aryl-substituted carbamates from formamides and alcohols. The reaction is compatible with industrially relevant N-alkyl formamides, as well as N-aryl formamides, and 1°, 2°, and benzylic alcohols. Mechanistic studies indicate that the first step in the reaction is the dehydrogenation of the formamide to a transient isocyanate by 1. The isocyanate then reacts with the alcohol to generate the carbamate. However, in a competing reaction, the isocyanate undergoes a reversible cycloaddition with 1 to generate an off-cycle species, which is the resting state in catalysis. Stoichiometric experiments indicate that high temperatures are required in catalysis to facilitate the release of the isocyanate from the cycloaddition product. We also identified several other off-cycle processes that occur in catalysis, such as the 1,2-addition of the formamide or alcohol substrate across the Fe-N bond of 1. It has already been demonstrated that the transient isocyanate generated from dehydrogenation of the formamide can be trapped with amines to form ureas and, in principle, the isocyanate could also be trapped with thiols to form thiocarbamates. Competition experiments indicate that trapping of the transient isocyanate with amines to produce ureas is faster than trapping with an alcohol to produce carbamates and thus ureas can be formed selectively in the presence of alcohols. In contrast, thiols bind irreversibly to the iron catalyst through 1,2 addition across the Fe-N bond of 1, and it is not possible to produce thiocarbamates. Overall, our mechanistic studies provide general guidelines for facilitating dehydrogenative coupling reactions using 1 and related catalysts.
- Bernskoetter, Wesley H.,Hazari, Nilay,Mercado, Brandon Q.,Townsend, Tanya M.
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p. 10614 - 10624
(2021/09/02)
-
- Atomically Dispersed Copper on N-Doped Carbon Nanosheets for Electrocatalytic Synthesis of Carbamates from CO2 as a C1 Source
-
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)
-
- Ceria supported Ru0-Ruδ+ clusters as efficient catalyst for arenes hydrogenation
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Selective hydrogenation of aromatic amines, especially chemicals such as aniline and bis(4-aminocyclohexyl)methane for non-yellowing polyurethane, is of particular interests due to the extensive applications. To conquer the existing difficulties in selective hydrogenation, the Ru0-Ruδ+/CeO2 catalyst with solid frustrated Lewis pairs was developed for aromatic amines hydrogenation with excellent activity and selectivity under relative milder conditions. The morphology, electronic and chemical properties, especially the Ru0-Ruδ+ clusters and reducible ceria were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electronic microscopy (SEM), X-ray photoelectron spectroscopy (XPS), CO2 temperature programmed desorption (CO2-TPD), H2 temperature programmed reduction (H2-TPR), H2 diffuse reflectance Fourier transform infrared spectroscopy (H2-DRIFT), Raman, etc. The 2% Ru/CeO2 catalyst exhibited good conversion of 95% and selectivity greater than 99% toward cyclohexylamine. The volcano curve describing the activity and Ru state was found. Owning to the “acidic site isolation” by surrounding alkaline sites, condensation between the neighboring amine molecules could be effectively suppressed. The catalyst also showed good stability and applicability for other aromatic amines and heteroarenes containing different functional groups.
- Cao, Yanwei,Zheng, Huan,Zhu, Gangli,Wu, Haihong,He, Lin
-
supporting information
p. 770 - 774
(2020/08/24)
-
- Method for continuously synthesizing alicyclic carbamate
-
The invention relates to a method for continuously synthesizing alicyclic carbamate. The method comprises the following steps: preheating raw material gas and raw material liquid to 20-130 DEG C through a preheater, introducing the raw material gas and the raw material liquid into a fixed bed reactor filled with a supported metal catalyst, and reacting at 30-150 DEG C under the reaction pressure of 0-5 MPa to obtain the alicyclic carbamate, wherein the supported metal catalyst comprises an active component metal salt and a carrier, and the active component metal salt is a rhodium active component metal salt. The method has the advantages of high mass and heat transfer efficiency, short reaction time, high product selectivity, intrinsic safety, high space-time efficiency and the like.
- -
-
Paragraph 0028-0058
(2021/06/06)
-
- Method for synthesizing alicyclic carbamate by taking isopropanol as hydrogen source
-
The invention relates to a method for synthesizing alicyclic carbamate by taking isopropanol as a hydrogen source. The method comprises the following steps: in a high-pressure reaction kettle, under N2 atmosphere, taking aromatic carbamate as a substrate, adding a reaction solvent and a catalyst; and taking isopropanol as a hydrogen source, performing stirring and reaction for 2-24 hours under the conditions of 50-200 DEG C and 0-5 MPa to obtain the alicyclic carbamate. The catalyst is a supported metal catalyst and comprises an active component metal salt and a carrier. The method has the advantages of mild reaction conditions, high safety, easiness in operation and the like.
- -
-
Paragraph 0030-0055
(2021/06/26)
-
- N-Aryl and N-Alkyl Carbamates from 1 Atmosphere of CO2
-
We have successfully isolated and characterized the zinc carbamate complex (phen)Zn(OAc)(OC(=O)NHPh) (1; phen=1,10-phenanthroline), formed as an intermediate during the Zn(OAc)2/phen-catalyzed synthesis of organic carbamates from CO2, amines, and the reusable reactant Si(OMe)4. Density functional theory calculations revealed that the direct reaction of 1 with Si(OMe)4 proceeds via a five-coordinate silicon intermediate, forming organic carbamates. Based on these results, the catalytic system was improved by using Si(OMe)4 as the reaction solvent and additives like KOMe and KF, which promote the formation of the five-coordinated silicon species. This sustainable and effective method can be used to synthesize various N-aryl and N-alkyl carbamates, including industrially important polyurethane raw materials, starting from CO2 under atmospheric pressure.
- Chen, Ming-Yu,Choe, Yoong-Kee,Choi, Jun-Chul,Fukaya, Norihisa,Hamura, Satoshi,Koizumi, Hiroki,Matsumoto, Kazuhiro,Matsumoto, Seiji,Shigeyasu, Shinji,Takeuchi, Katsuhiko,Yuan, Hao-Yu
-
supporting information
p. 18066 - 18073
(2021/12/08)
-
- METHOD FOR PRODUCING CARBAMATE
-
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
- -
-
Paragraph 0014-0024
(2021/08/13)
-
- Urethanes synthesis from oxamic acids under electrochemical conditions
-
Urethane synthesis via oxidative decarboxylation of oxamic acids under mild electrochemical conditions is reported. This simple phosgene-free route to urethanes involves an in situ generation of isocyanates by anodic oxidation of oxamic acids in an alcoholic medium. The reaction is applicable to a wide range of oxamic acids, including chiral ones, and alcohols furnishing the desired urethanes in a one-pot process without the use of a chemical oxidant.
- Ogbu, Ikechukwu Martin,Lusseau, Jonathan,Kurtay, Gülbin,Robert, Frédéric,Landais, Yannick
-
supporting information
p. 12226 - 12229
(2020/10/26)
-
- 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)
-
- 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)
-
- Phosgene-free synthesis of carbamates using co2 and titanium alkoxides
-
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
-
p. 1481 - 1486
(2018/10/25)
-
- 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
-
supporting information
p. 9781 - 9784
(2017/09/07)
-
- 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
-
-
- A Simple Zinc Catalyst for Carbamate Synthesis Directly from CO2
-
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
-
p. 1501 - 1508
(2017/04/14)
-
- Direct synthesis of carbamate from CO2 using a task-specific ionic liquid catalyst
-
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)
-
- Base-Catalyzed Transcarbamoylation
-
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
-
supporting information
p. 2004 - 2007
(2017/09/13)
-
- Effective synthesis of dimethylhexane-1,6-dicarbamate from 1,6-hexanediamine and dimethyl carbonate using 3-amino-1,2,4-triazole potassium as a solid base catalyst at ambient temperature
-
A new basic catalyst 3-amino-1,2,4-triazole potassium (KATriz) was prepared, characterized and employed for synthesis of dimethylhexane 1,6-dicarbamate (MHDC) by methoxycarbonylation of 1,6-hexanediamine (HDA) and dimethyl carbonate (DMC). Results showed that KATriz exhibited high catalytic activity and selectivity, 100% HDA conversion with nearly 100% MHDC selectivity that could be obtained at room temperature. The catalyst can be reused for several runs without any deactivation. Besides, the influence of reaction conditions, the structure of amines and the possible catalytic mechanism were also investigated.
- Wang, Peixue,Fei, Yuqing,Li, Qinghe,Deng, Youquan
-
p. 6681 - 6686
(2018/06/08)
-
- Copper(II)-catalysed oxidative carbonylation of aminols and amines in water: A direct access to oxazolidinones, ureas and carbamates
-
Copper(II) chloride catalyses the oxidative carbonylation of aminols, amine and alcohols to give 2-oxazolidinones, ureas and carbamates. Reaction proceeds smoothly in water under homogeneous conditions (Ptot = 4 MPa; PO2 = 0.6 MPa, PCO), at 100°C in relatively short reaction times (4 h) and without using bases or any other additives. This methodology represents an economic and environmentally benign non-phosgene alternative for the preparation of these three important N-containing carbonyl compounds.
- Casiello, Michele,Iannone, Francesco,Cotugno, Pietro,Monopoli, Antonio,Cioffi, Nicola,Ciminale, Francesco,Trzeciak, Anna M.,Nacci, Angelo
-
-
- N-Substituted carbamate synthesis using urea as carbonyl source over TiO2-Cr2O3/SiO2 catalyst
-
The use of urea as an active form of carbon dioxide is a feasible way to substitute phosgene in the chemical industry. This paper reports an effective route for the synthesis of N-substituted carbamates from amines, urea and alcohols. Under the optimized reaction conditions, several important N-substituted carbamates were successfully synthesized in 95-98% yields over a TiO2-Cr2O3/SiO2 catalyst. The catalyst could be reused for several runs without deactivation. The catalysts were characterized by BET, XPS, XRD, and TPD, which suggested that the strength and amount of the acidic and basic sites might be the major reason for the high catalytic activity of TiO2-Cr2O3/SiO2.
- Wang, Peixue,Ma, Yubo,Liu, Shimin,Zhou, Feng,Yang, Benqun,Deng, Youquan
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p. 3964 - 3971
(2015/07/15)
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- Ruthenium-Na2CO3-catalyzed one-pot synthesis of ring-hydrogenated carbamates from aromatic amines and organic carbonates under H2
-
A facile and efficient one-pot procedure for the synthesis of ring hydrogenated carbamates from aromatic amine and alkylene carbonate under H2 gas pressure has been developed using a heterogeneous catalyst system comprising ruthenium and alkali metal carbonates. The effects of temperature, H2 pressure, catalyst (types of loaded metal and their supports), molar ratio of substrate/catalyst, and solvent were also investigated. Among the alkali metal carbonates, the sodium carbonate was found as best promoter for nucleophilic attack and ring-opening (NARO) reaction and thus increased the yield of ring hydrogenated carbamate up to 88% when using Ru/C as ring hydrogenation (RH) catalyst. This catalyst system could be reused at least five times without signi?cant loss of activity, which makes this process cost-effective and eco-friendly.
- Cho, Jin Ku,Kim, Hoon Sik,Kim, Yong Jin,Mishra, Vivek,Shin, Seung-Han,Suh, Young-Woong
-
-
- L-Proline-TBAB-catalyzed phosgene free synthesis of methyl carbamates from amines and dimethyl carbonate
-
The reaction of amines and dimethyl carbonate (DMC) in the presence of catalytic amounts of l-proline and tetrabutylammonium bromide (TBAB) afforded methyl carbamates in good to excellent yields under mild conditions. The presence of both l-proline and TBAB co-catalysts is vital for this transformation.
- Kumar, Subodh,Jain, Suman L.
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p. 2935 - 2938
(2013/09/12)
-
- Hypervalent iodine catalyzed hofmann rearrangement of carboxamides using oxone as terminal oxidant
-
Hofmann rearrangement of carboxamides to carbamates using Oxone as an oxidant can be efficiently catalyzed by iodobenzene. This reaction involves hypervalent iodine species generated in situ from catalytic amount of PhI and Oxone in the presence of 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) in aqueous methanol solutions. Under these conditions, Hofmann rearrangement of various carboxamides affords corresponding carbamates in high yields.
- Yoshimura, Akira,Middleton, Kyle R.,Luedtke, Matthew W.,Zhu, Chenjie,Zhdankin, Viktor V.
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p. 11399 - 11404
(2013/02/23)
-
- Highly efficient synthesis of ureas and carbamates from amides by iodosylbenzene-induced hofmann rearrangement
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A simple and efficient method for the synthesis of 1,3-disubstituted ureas and carbamates from amides by using iodosylbenzene as the oxidant is described. Symmetric and asymmetric ureas and carbamates can be prepared by this procedure in up to 98 % yield. Ureidopeptides can also be prepared in good yield by this method. A simple and efficient method for the synthesis of 1,3-disubstituted ureas and carbamates from amides by using iodosylbenzene as the oxidant is described. By using this method, heterocyclic products can be easily obtained in excellent yield. Ureidopeptides can also be prepared in good yield by this procedure. Copyright
- Liu, Peng,Wang, Zhiming,Hu, Xianming
-
experimental part
p. 1994 - 2000
(2012/05/05)
-
- (Tosylimino)phenyl-λ3-iodane as a reagent for the synthesis of methyl carbamates via hofmann rearrangement of aromatic and aliphatic carboxamides
-
A new, mild procedure for the Hofmann rearrangement of aromatic and aliphatic carboxamides using (tosylimino)phenyl-λ3-iodane, PhINTs, as a reagent is reported. Because of the mild reaction conditions, this method is particularly useful for the Hofmann rearrangement of substituted benzamides, which usually afford complex reaction mixtures with other hypervalent iodine oxidants. The mild reaction conditions and high selectivity in the reaction of carboxamides with PhINTs allow the isolation of the initially formed labile isocyanates or their subsequent conversion to stable carbamates by treatment with alcohols.
- Yoshimura, Akira,Luedtke, Matthew W.,Zhdankin, Viktor V.
-
experimental part
p. 2087 - 2091
(2012/05/05)
-
- PROCESS FOR PREPARING A CARBAMATE COMPOUND
-
There is provided a process for preparing a carbamate compound, which is easy and commercially advantageous in that a carbamate compound can be produced with high yield from an amine compound and a carbonate compound. A process for preparing a carbamate compound which comprises the step of reacting an amine compound which has at least one amino group per molecule wherein the amine compound is selected from the group consisting of an aliphatic amine which may be substituted by an alicyclic group or an aromatic group or which may be interrupted by an alicyclic group or an aromatic group, and an alicyclic amine which may be substituted by an aliphatic group, with a carbonate compound in the presence of at least one organic solvent selected from the group consisting of a saturated cyclic hydrocarbon, an unsaturated cyclic hydrocarbon, and a non-cyclic ether by using a hydrolase.
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Page/Page column 8
(2012/12/13)
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- Green and practical synthesis of carbamates from ureas and organic carbonates
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A practical method for the synthesis of carbamates from ureas and organic carbonates was developed with 100% atom economy using La2O 3/SiO2 as catalyst without any additional solvent. The scope of the protocol is demonstrated in the synthesis of 14 carbamates with various functional groups in excellent yields (76-95%).
- Guo, Xiaoguang,Shang, Jianpeng,Li, Jian,Wang, Liguo,Ma, Yubo,Shi, Feng,Deng, Youquan
-
experimental part
p. 1102 - 1111
(2011/05/02)
-
- Synthesis of methyl-1-(tert -butoxycarbonylamino)-2- vinylcyclopropanecarboxylate via a hofmann rearrangement utilizing trichloroisocyanuric acid as an oxidant
-
A trichloroisocyanuric acid (TCCA) mediated Hofmann rearrangement was utilized to synthesize methyl-1-(tert-butoxycarbonylamino)-2- vinylcyclopropanecarboxylate. A variety of functional groups are tolerated in this reaction including vinyl, cyclopropyl, pyridyl, aryl, benzyl, and nitro groups.
- Crane, Zackary D.,Nichols, Paul J.,Sammakia, Tarek,Stengel, Peter J.
-
supporting information; experimental part
p. 277 - 280
(2011/03/20)
-
- Atom-economy synthesis of N-substituted carbamate from urea derivative and dimethyl carbonate catalyzed by La/SiO2: Characterization and activity
-
A series of silica gel immobilized lanthanum catalysts were prepared for the atom-economy synthesis of N-substituted carbamates from urea derivatives and dimethyl carbonate. The La/SiO2 catalysts with lanthanum loadings varied from 1.3 wt% to 8.5 wt% were characterized by AES, BET, XRD, TEM, FT-IR, XPS and TPD. According to the characterization, lanthanum species with particle sizes of 5-10 nm on the surface of silica gel were formed. The catalysts were all amorphous and the surface areas were 336.5-530.2 m2/g. NH3-TPD analysis showed that all samples exhibited similar acid strength with different acid amounts. FT-IR measurement indicated that the component of lanthanum species on the catalyst surface were La(OH)3, LaOOH and hydrated La2O3. Also, the peak value of the absolute amount of LaOOH was obtained with 4.3 wt% lanthanum loading. The BET surface area decreased dramatically when the lanthanum loading was above 4.3 wt%. In consideration of the results obtained from the catalytic reactions, it could be concluded that LaOOH was the possible active species and high surface area was important for the high catalytic activity.
- Guo, Xiaoguanga,Shang, Jianpenga,Li, Jiana,Wang, Liguoa,Ma, Yuboa,Shi, Feng,Deng, Youquan
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experimental part
p. 164 - 170
(2010/10/19)
-
- Hofmann rearrangement of carboxamides mediated by hypervalent iodine species generated in situ from iodobenzene and oxone: Reaction scope and limitations
-
Alkylcarboxamides can be converted to the respective amines by Hofmann rearrangement using hypervalent iodine species generated in situ from PhI and Oxone in aqueous acetonitrile. On the basis of this reaction, a convenient experimental procedure for the preparation of alkylcarbamates using Oxone as the oxidant in the presence of iodobenzene in methanol has been developed. An efficient method for direct conversion of substituted benzamides to the respective quinone derivatives by treatment with Oxone and iodobenzene in aqueous acetonitrile has also been found.
- Zagulyaeva, Aleksandra A.,Banek, Christopher T.,Yusubov, Mekhman S.,Zhdankin, Viktor V.
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supporting information; experimental part
p. 4644 - 4647
(2010/12/19)
-
- METHOD FOR PREPARING A CARBAMATE, A CATALYST APPLIED IN THE METHOD, A METHOD FOR PREPARING THE CATALYST AND USE THEREOF
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The present invention pertains to a novel method for preparing a carbamate, in which the method comprises reacting an aliphatic substituted urea and/or its derivatives, with a hydroxyl group containing compound to obtain a carbamate. In addition, the pres
- -
-
Page/Page column 6
(2010/12/26)
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- Carbamate synthesis from amines and dialkyl carbonate over inexpensive and clean acidic catalyst-Sulfamic acid
-
Sulfamic acid has been proved to be the most efficient and recyclable catalyst in carbamate synthesis from alkylamine and dialkyl carbonate. High selectivity, cost-efficiency and simple product separation were the advantageous features obtained in this process. Sulfamic acid could be reused several times and keep its initial activity in the recycle runs. In addition, sulfamic acid has also exhibited the potential catalytic ability for alkylation of aromatic amines.
- Wang, Bo,He, Jing,Sun, Run Cang
-
scheme or table
p. 794 - 797
(2011/11/13)
-
- Indium-catalyzed reaction for the synthesis of carbamates and carbonates: selective protection of amino groups
-
We developed a simple, efficient, and selective method for preparing organic carbamates and carbonates using a catalytic amount of indium. A wide range of carbamates and carbonates were synthesized in high yields. The method is also applicable to the selective protection of amino groups under mild conditions.
- Kim, Joong-Gon,Jang, Doo Ok
-
experimental part
p. 2688 - 2692
(2009/08/09)
-
- N-tosyloxycarbamates as reagents in rhodium-catalyzed C-H amination reactions
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Metal nitrenes for use in C-H insertion reactions were obtained from N-tosyloxycarbamates in the presence of an inorganic base and a rhodium(II) dimer complex catalyst. The C-H amination reaction proceeds smoothly, and the potassium tosylate that forms as a byproduct is easily removed by filtration or an aqueous workup. This new methodology allows the amination of ethereal, benzylic, tertiary, secondary, and even primary C-H bonds. The intramolecular reaction provides an interesting route to various substituted oxazolidinones, whereas the intermolecular reaction gives trichloroethoxycarbonyl-protected amines that can be isolated with moderate to excellent yields and that cleave easily to produce the corresponding free amine. The development, scope, and limitations of the reactions are discussed herein. Isotopic effects and the electronic nature of the transition state are used to discuss the mechanism of the reaction.
- Huard, Kim,Lebel, Helene
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scheme or table
p. 6222 - 6230
(2009/05/27)
-
- Radical transfer hydroamination with aminated cyclohexadienes using polarity reversal catalysis: Scope and limitations
-
The synthesis of various new 1-aminated-2,5-cyclohexadienes is described. These reagents can be used in radical transfer hydroaminations of unactivated and electron-rich double bonds. With thiols as polarity reversal catalysts good yields are obtained. The radical hydroamination occurs with good to excellent anti-Markovnikov selectivity. Many functional groups such as alcohols, silyl ethers, phosphonates, arylbromides, imides, amides, and also acidic protons are tolerated under the reaction conditions. DFT calculations provide insights into the aromatization of silyl, alkyl, and aminyl substituted cyclohexadienyl radicals to generate the corresponding C-, Si-, and N-centered radicals.
- Guin, Joyram,Mueck-Lichtenfeld, Christian,Grimme, Stefan,Studer, Armido
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p. 4498 - 4503
(2008/02/03)
-
- De novo synthesis of troc-protected amines: Intermolecular rhodium-catalyzed C-H amination with N-tosyloxycarbamates
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The rhodium-catalyzed intermolecular C-H insertion of the nitrene derived from 2,2,2-trichloroethyl-N-tosyloxycarbamate proceeded in good to excellent yields to produce a variety of Troc-protected amines. With cyclic aliphatic alkanes, it is possible to use only 2 equiv of substrate, whereas the reaction with aromatic alkanes is run neat. Not only does the nitrene insertion proceed in benzylic, secondary, and tertiary C-H bonds but also primary C-H insertion products were obtained in good yields. Finally, the use of chiral rhodium catalysts to provide an enantioselective version of this process is discussed.
- Lebel, Helene,Kim, Huard
-
p. 639 - 642
(2008/02/03)
-
- An efficient modification of the Hofmann rearrangement: synthesis of methyl carbamates
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A series of methyl carbamates was synthesized using NaOCl as an oxidant in the presence of KF/Al2O3/MeOH at reflux in excellent yields.
- Gogoi, Pranjal,Konwar, Dilip
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p. 531 - 533
(2007/10/03)
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- A novel and efficient (NHC)CuI (NHC = N-heterocyclic carbene) catalyst for the oxidative carbonylation of amino compounds
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Oxidative carbonylation of amino compounds to prepare corresponding 2-oxazolidinones, ureas, and carbamates selectively in the presence of (NHC)CuI without any additives was firstly achieved in good yields and selectivities.
- Zheng, Shuzhan,Li, Fuwei,Liu, Jianming,Xia, Chungu
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p. 5883 - 5886
(2008/02/09)
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- Mild and convenient synthesis of organic carbamates from amines and carbon dioxide using tetraethylammonium superoxide
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A safe and simple method of preparing organic carbamates has been achieved from amines and carbon dioxide using tetraethylammonium superoxide generated in situ. Copyright Taylor & Francis Group, LLC.
- Singh, Krishna Nand
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p. 2651 - 2654
(2008/02/12)
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- 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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p. 1253 - 1256
(2007/10/03)
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- Synthesis of methyl carbamates from primary aliphatic amines and dimethyl carbonate in supercritical CO2: Effects of pressure and cosolvents and chemoselectivity
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(Chemical Equation Presented) At 130 °C, in the presence of CO 2 (5-200 bar), primary aliphatic amines react with dimethyl carbonate (MeOCO2Me, DMC) to yield methyl carbamates (RNHCO2Me) and N-methylation side-products (RNHMe and RNMe2). The pressure of CO2 largely influences both the reaction conversion and the selectivity toward urethanes: in general, conversion goes through a maximum (70-80%) in the midrange (40 bar) and drops at lower and higher pressures, whereas selectivity is continuously improved (from 50% up to 90%) by an increase of the pressure. This is explained by the multiple role of CO2 in (i) the acid/base equilibrium with aliphatic amines, (ii) the reactivity/solubility of RNHCO2- nucleophiles with/in DMC, and (iii) the inhibition of competitive N-methylation reaction of the substrates. Cosolvents also affect the reaction: in particular, a drop in selectivity is observed with polar protic media (i.e., MeOH), plausibly because of solvation effects (through H-bonds) of RNHCO2- moieties. The reaction shows also a good chemoselectivity: bifunctional aliphatic amines bearing either aromatic NH2 or OH substituents [XC6H4(CH2)nNH2, X = NH2, OH; n = 1 2], undergo methoxycarbonylation reactions exclusively at aliphatic amino groups and give the corresponding methyl carbamates [XC 6H4(CH2)nNHCO2Me] in 39-65% isolated yields.
- Selva, Maurizio,Tundo, Pietro,Perosa, Alvise,Dall'Acqua, Federico
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p. 2771 - 2777
(2007/10/03)
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- PROCESS FOR PREPARING CARBAMATES
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A process for the preparation of carbamates from organic urea and organic carbonate in presence of a solid base catalyst is disclosed. The process works at the milder reaction conditions and utilizes inexpensive catalysts that can be recycled several times.
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Page/Page column 17-18
(2008/06/13)
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- Process for preparing carbamates
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A process for the preparation of carbamates from organic urea and organic carbonate in presence of a solid base catalyst is disclosed. The process works at the milder reaction conditions and utilizes inexpensive catalysts that can be recycled several times.
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Page/Page column 7
(2008/06/13)
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- Preparation of methyl N-substituted carbamates from amides through N-chloroamides
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Amides are chlorinated on the nitrogen using trichloroisocyanuric acid, and the N-chloroamides are then rearranged to the corresponding methyl N-substituted carbamates by sodium methoxide in methanol. Copyright Taylor & Francis, Inc.
- Hiegel, Gene A.,Hogenauer, Tyrone J.
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p. 2091 - 2098
(2007/10/03)
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- Mechanism of formation of organic carbonates from aliphatic alcohols and carbon dioxide under mild conditions promoted by carbodiimides. DFT calculation and experimental study
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Dicyclohexylcarbodiimide (CyN=C=NCy, DCC) promotes the facile formation of organic carbonates from aliphatic alcohols and carbon dioxide at temperatures as low as 310 K and moderate pressure of CO2 (from 0.1 MPa) with an acceptable rate. The conversion yield of DCC is quantitative, and the reaction has a very high selectivity toward carbonates at 330 K; increasing the temperature increases the conversion rate, but lowers the selectivity. A detailed study has allowed us to isolate or identify the intermediates formed in the reaction of an alcohol with DCC in the presence or absence of carbon dioxide. The first step is the addition of alcohol to the cumulene (a known reaction) with formation of an O-alkyl isourea [RHNC(ORO=NR] that may interact with a second alcohol molecule via H-bond (a reaction never described thus far). Such an adduct can be detected by NMR. In alcohol, in absence of CO 2, it converts into a carbamate and a secondary amine, while in the presence of CO2, the dialkyl carbonate, (RO)2CO, is formed together with urea [CyHN-CO-NHCy]. The reaction has been tested with various aliphatic alcohols such as methanol, ethanol, and allyl alcohol. It results in being a convenient route to the synthesis of diallyl carbonate, in particular. O-Methyl-N,N′-dicyclohexyl isourea also reacts with phenol in the presence of CO2 to directly afford for the very first time a mixed aliphatic-aromatic carbonate, (MeO)(PhO)CO. A DFT study has allowed us to estimate the energy of each intermediate and the relevant kinetic barriers in the described reactions, providing reasonable mechanistic details. Calculated data match very well the experimental results. The driving force of the reaction is the conversion of carbodiimide into the relevant urea, which is some 35 kcal/mol downhill with respect to the parent compound. The best operative conditions have been defined for achieving a quantitative yield of carbonate from carbodiimide. The role of temperature, pressure, and catalysts (Lewis acids and bases) has been established. As the urea can be reconverted into DCC, the reaction described in this article may further be developed for application to the synthesis of organic carbonates under selective and mild conditions.
- Aresta, Michele,Dibenedetto, Angela,Fracchiolla, Elisabetta,Giannoccaro, Potenzo,Pastore, Carlo,Papai, Imre,Schubert, Gabor
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p. 6177 - 6186
(2007/10/03)
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- Copper-Mediated N-Alkynylation of Carbamates, Ureas, and Sulfonamides. A General Method for the Synthesis of Ynamides
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(Matrix Presented) A general amination strategy for the N-alkynylation of carbamates, sulfonamides, and chiral oxazolidinones and imidazolidinones is described. A variety of substituted ynamides are available by deprotonation of amides with KHMDS followed by reaction with CuI and an alkynyl bromide.
- Dunetz, Joshua R.,Danheiser, Rick L.
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p. 4011 - 4014
(2007/10/03)
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- Synthesis and reactions of some azolecarboxylic acid derivatives
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Reaction of several azoles with phosgene or triphosgene was studied. Besides benzotriazole (previously described reaction), only indazole, 5-nitroindazole and 5-methylbenzotriazole gave the corresponding 1-azolecarbonyl chlorides 1a-d. Azoles of weak acidity (imidazole, 1,2,3-triazole, 1,2,4-triazole, benzimidazole) could not give stable acyl chlorides, while strong acidic azoles like tetrazole and 4,5,6,7- tetrachlorobenzotriazole did not react at all. Chlorides 1b-d readily reacted with alcohols, amines, amino acids and their esters like the previously described 1-benzotriazolecarboxylic acid chloride (1a), giving 1-azolecarboxylic acid esters (2) or amides (3), N-(1-azolecarbonyl)amino acids (4, 5), their esters (8, 9) or amides (10, 11). However, a significant difference was observed in the reactivity of azole derivatives 2-11 with amines, alcohols and N-protected amino acids or in their stability in acidic and basic aqueous media. Benzotriazole and methylbenzotriazole derivatives were more reactive than indazole or nitroindazole derivatives. The higher reactivity was in correlation with the shift of the IR carbonyl absorption band to higher wave numbers.
- Kalcic, Igor,Zovko, Marijana,Takac, Milena Jadrijevic-Mladar,Zorc, Branka,Butula, Ivan
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p. 217 - 228
(2007/10/03)
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- The syntheses of carbamates from reactions of primary and secondary aliphatic amines with dimethyl carbonate in ionic liquids
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At 170°C and using ionic liquids as solvent and catalyst, primary and secondary aliphatic amines could react with dimethyl carbonate to give alkyl carbamates with good yield. Due to its insolubility, the desired carbamate solid could be recovered by simpl
- Sima, Tianlong,Guo, Shu,Shi, Feng,Deng, Youquan
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p. 8145 - 8147
(2007/10/03)
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- Mixed anhydrides: Key intermediates in carbamates forming processes of industrial interest
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Mixed anhydrides of carbonic acid with phosphonic or carbamic acid, are mimic of relevant biological systems, and behave as key intermediates in transesterification processes that afford carbamates of industrial interest. They are formed in the phosphonic acids mediated or direct transesterification reaction of organic carbonates with amines to afford carbamates and have been isolated and characterised in the solid state and solution. Their conversion into the products has been demonstrated to occur with high regioselectivity. The application of such intermediates in some synthetic processes is discussed.
- Aresta, Michele,Dibenedetto, Angela
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p. 685 - 690
(2007/10/03)
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- Carbamate synthesis from amines and dimethyl carbonate under ytterbium triflate catalysis
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A facile synthesis of carbamates from amines and dimethyl carbonate has been achieved using ytterbium triflate as catalyst.
- Curini, Massimo,Epifano, Francesco,Maltese, Federica,Rosati, Ornelio
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p. 4895 - 4897
(2007/10/03)
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- The synthesis of alkyl carbamates from primary aliphatic amines and dialkyl carbonates in supercritical carbon dioxide
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At 130°C and in the presence of compressed CO2, primary aliphatic amines [RNH2, R=C10H21, C8H17, cHex, 1-(C10H7)CH2] react with organic carbonates (R′OCOsu
- Selva, Maurizio,Tundo, Pietro,Perosa, Alvise
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p. 1217 - 1219
(2007/10/03)
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