- Dehydrogenative Synthesis of Carbamates from Formamides and Alcohols Using a Pincer-Supported Iron Catalyst
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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)
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- Urethanes synthesis from oxamic acids under electrochemical conditions
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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
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supporting information
p. 12226 - 12229
(2020/10/26)
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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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supporting information
p. 1297 - 1300
(2017/06/23)
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- Oximes as reusable templates for the synthesis of ureas and carbamates by an: In situ generation of carbamoyl oximes
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Oximes have been identified as reusable templates for the synthesis of ureas and carbamates by an in situ generation of carbamoyl oximes under metal-free conditions. The recovered oxime has been utilised for three trials in the synthesis of urea derivatives without any loss in the yield and efficiency. In addition, this template approach could override the usage of hazardous and less stable isocyanates as substrates.
- Senadi, Gopal Chandru,Mutra, Mohana Reddy,Lu, Ting-Yi,Wang, Jeh-Jeng
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supporting information
p. 4272 - 4277
(2017/09/28)
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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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- N-Substituted carbamate synthesis using urea as carbonyl source over TiO2-Cr2O3/SiO2 catalyst
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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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- Green and practical synthesis of carbamates from ureas and organic carbonates
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A practical method for the synthesis of carbamates from ureas and organic carbonates was developed with 100% atom economy using La2O 3/SiO2 as catalyst without any additional solvent. The scope of the protocol is demonstrated in the synthesis of 14 carbamates with various functional groups in excellent yields (76-95%).
- Guo, Xiaoguang,Shang, Jianpeng,Li, Jian,Wang, Liguo,Ma, Yubo,Shi, Feng,Deng, Youquan
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experimental part
p. 1102 - 1111
(2011/05/02)
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- Polyethylene glycol-enhanced chemoselective synthesis of organic carbamates from amines, CO2, and alkyl halides
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An efficient and environmentally benign method for the synthesis of organic carbamates was developed. Amines, CO2, and alkyl halides underwent a three-component reaction with the aid of K2CO3 and polyethylene glycol (PEG, MW=400), affording the organic carbamates under ambient conditions. PEG could presumably act as a solvent and phase-transfer catalyst (PTC). Notably, the presence of PEG could also depress the alkylation of both the amine and the carbamate, thus resulting in enhanced selectivity toward the target carbamate. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications to view the free supplemental file.
- Kong, De-Lin,He, Liang-Nian,Wang, Jin-Quan
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experimental part
p. 3298 - 3307
(2011/09/15)
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- 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
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Page/Page column 6
(2010/12/26)
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- Process for the preparation of carbamates
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The present invention provides an improved process for the preparation of carbamates with high selectivity of pharmaceutical interest by an eco-friendly, non-toxic, phosgene-/isocyanate-/CO-free clean route through a reaction of amine, organic halide comp
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Page/Page column 5
(2008/06/13)
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- Syntheses of polycarbonate and polyurethane precursors utilizing CO2 over highly efficient, solid as-synthesized MCM-41 catalyst
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As-synthesized MCM-41 was used as a reusable, heterogeneous catalyst for the eco-friendly synthesis of cyclic carbonate precursors of polycarbonates via a cycloaddition reaction of CO2 with epoxides. This catalyst is also efficient for the synt
- Srivastava,Srinivas,Ratnasamy
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p. 4213 - 4217
(2007/10/03)
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- Electrochemically induced Hofmann rearrangement
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Electrochemically induced Hofmann rearrangement under new solvent systems containing a variety of alcohols was developed. Since the reaction proceeds under mild conditions (neutral), a variety of carbamates possessing various alkoxy moieties could be easi
- Matsumura, Yoshihiro,Maki, Toshihide,Satoh, Yuki
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p. 8879 - 8882
(2007/10/03)
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- The Reaction of Isocyanides with Halogens or N-Halosuccinimides and Alcohols
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The reaction of aliphatic isocyanides with bromine or chlorine in primary alcohols, followed by hydrolysis, afforded the corresponding carbamates in moderate yields, together with various amounts of amines.Bromine was superior to chlorine as a halogen source for the formation of carbamates, unexpectedly, the addition of HgCl2 resulted in a decrease in the carbamate yield.When N-halosuccinimides were used in the place of halogens, an additional formation of the succinimide-incorporated product was observed to some extent.
- Yamada, Hideyo,Wada, Yasuo,Tanimoto, Shigeo,Okano, Masaya
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p. 2480 - 2483
(2007/10/02)
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- REACTION OF ORGANIC CARBONATES WITH AMINES I. REACTION OF ALKYL PHENYL CARBONATES WITH PRIMARY ALIPHATIC AMINES
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The reaction of alkyl phenyl carbonates with primary aliphatic amines, leading to the formation of N-alkylurethanes, was investigated.The reaction has overall third order, which is explained by the catalytic action of the amine.The effect of the structure of the alkyl radical and the character of the substituent in the phenyl group of the alkyl phenyl carbonates and also the effect of the polarity of the solvent on the rate of the transformation were investigated.The reaction obeys the Hammett equation.
- Mikheev, V. V.,Svetlakov, N. V.,Garipov, R. M.
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p. 215 - 220
(2007/10/02)
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