- The role of μ-hydroxy and μ-alkoxy binuclear complexes in tin(IV)-catalysed urethane formation
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It is proposed that at the catalyst concentrations normally used the distannoxane-catalysed formation of urethanes from isocyanates and alcohols involves the monomeric form of the distannoxane rather than the dimeric form as previously suggested, and that
- Houghton, Roy P.,Mulvaney, Andrew W.
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Read Online
- Noncatalytic and Autocatalytic Rate Constants of the Reaction of Phenyl Isocyanate with Butan-1-ol
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The kinetics of the reaction of phenyl isocyanate with butan-1-ol have been studied in the temperature range from 30 to 60°C. The rate constants of the noncatalytic and autocatalytic reaction paths have been determined from the concentration dependences o
- Samuilov, A. Ya.,Samuilov, Ya. D.
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Read Online
- 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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Read Online
- MECHANISTIC INVESTIGATION OF DISTANNOXANE-CATALYZED URETHANE FORMATION STUDIED BY (119)Sn NMR SPECTRA
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The mechanism of urethane formation catalyzed by tetraorganodistannoxanes was investigated.The (119)Sn NMR spectra and the model reaction between methanol and phenyl isocyanate revealed that the formation of the alkoxy distannoxanes is the initial step.
- Otera, Junzo,Yano, Toru,Okawara, Rokuro
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Read Online
- Kinetics of the Spontaneous Urethane Formation
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The kinetics of the reaction of phenylisocyanate with 1-butanol have been studied at low concentrations in carbon tetrachloride solution at three temperatures.The present paper describes the relation between the reaction rate and the concentration of the
- Thiele, Lothar
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Read Online
- A practical organotin(IV) catalyst for urethan and polyurethan technology
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Diallyltin(IV)di(2-ethyl hexanoate) 1, an air and moisture stable compound efficiently catalyses the addition of aryl isocyanates to various alcohols giving rise to substituted urethans in good to excellent yields.
- Roy,Majumdar
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Read Online
- Catalytic production of urethanes from amines and alkyl halides in supercritical carbon dioxide
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Some common onium salts catalysed selective urethane production from amines and alkyl halides in supercritical carbon dioxide, which acted not only as an alternative to organic solvents but also as a phosgene replacement; the reaction efficiency was 50-10
- Yoshida, Masaaki,Hara, Namiko,Okuyama, Sanae
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Read Online
- 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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- Zn(ii)@TFP-DAQ COF: An efficient mesoporous catalyst for the synthesis of: N -methylated amine and carbamate through chemical fixation of CO2
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Selective N-methylation and carbamate formation reactions were demonstrated via the chemical incorporation of CO2 using a Zn-loaded TFP-DAQ COF (covalent organic framework) as an active catalyst under mild reaction conditions. The selective N-methylation and N-formylation reactions were performed by simply varying the type of solvent. The Zn(ii)@TFP-DAQ COF catalyst was characterized via different characterization techniques such as PXRD, FTIR, UV-vis, N2 adsorption-desorption studies, FESEM and TEM. The catalyst material showed pores in the mesoporous region with a high surface area of 1117.375 m2 g-1. The as-synthesized material was applied as a cheap catalyst for the N-methylation of secondary amines and in carbamate formation reactions with high yields of the desired products up to 98.5% and 97%, respectively, with >99% selectivity. The catalyst was found to be completely heterogeneous and reusable for multiple reaction cycles.
- Sarkar, Priyanka,Chowdhury, Arpita Hazra,Riyajuddin, Sk.,Biswas, Surajit,Ghosh, Kaushik,Islam, Sk. Manirul
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p. 744 - 752
(2020/01/31)
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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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- 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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- Modified Graphene Oxide Based Zinc Composite: an Efficient Catalyst for N-formylation and Carbamate Formation Reactions Through CO2 Fixation
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Catalytic fixation of CO2 through chemical reactions is always a challenging task of synthetic chemistry. This paper represents the design and synthesis of an eco-friendly low cost zinc metal containing heterogeneous catalyst of aminically modified Graphene Oxide. Characterization of the catalyst has been carried out by Raman and FTIR spectra, AAS, XRD, TEM, SEM, EDX and N2 adsorption desorption studies. It was found that the catalyst was very proficient for the CO2 fixation through N-formylation and carbamate formation reactions of amines. Catalytic N-formylation reaction of both aromatic and aliphatic amines gave high yield of corresponding formylated products in presence of polymethylhydrosiloxane (PMHS) as reducing agent under 1 bar CO2 pressure and mild temperature. Formation of carbamates from aniline or its derivatives and alkyl/aryl bromide with good product selectivity was also achieved under same CO2 pressure in presence of our synthesized catalyst at room temperature with solvent-free condition. The catalyst is reusable and e?cient even after six cycles.
- Khatun, Resmin,Biswas, Surajit,Islam, Sarikul,Biswas, Imdadul Haque,Riyajuddin, Sk,Ghosh, Kaushik,Islam, Sk Manirul
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supporting information
p. 1303 - 1312
(2019/01/25)
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- Catalytic synthesis of benzimidazoles and organic carbamates using a polymer supported zinc catalyst through CO2 fixation
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Utilization of carbon dioxide in chemical fixation for synthesis of fine chemicals like benzimidazoles, organic carbamates, etc. is in high demand in recent years as carbon dioxide is a cost effective, sustainable, and green renewable C1 source. In this article we present the design and synthesis of an organically modified polystyrene bound heterogeneous [PS-Zn(ii)-SALTETA] catalyst. The catalyst has been characterized thoroughly by Fourier transform infrared spectroscopy, atomic absorption spectroscopy, thermo gravimetric analysis, PXRD, SEM and EDAX studies. The catalyst was used for cyclization of o-phenylenediamines through insertion of carbon dioxide in order to produce benzimidazoles in the presence of dimethylamine borane (DMAB). The developed catalytic procedure is sustainable, economical and efficient owing to the utilization of ethanol/water as a biodegradable and environment friendly solvent system. Besides benzimidazole production the catalyst was also very active for manufacture of organic carbamates from anilines and n-butyl bromide under atmospheric CO2 pressure under solvent free conditions at room temperature and the catalytic protocol showed outstanding functional group tolerance. Moreover the catalyst is highly recyclable and reusable.
- Biswas, Imdadul Haque,Biswas, Surajit,Islam, Md Sarikul,Riyajuddin, Sk,Sarkar, Priyanka,Ghosh, Kaushik,Islam, Sk Manirul
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p. 14643 - 14652
(2019/09/30)
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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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- 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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- Selective Synthesis of Secondary Arylcarbamates via Efficient and Cost Effective Copper-Catalyzed Mono Arylation of Primary Carbamates with Aryl Halides and Arylboronic Acids
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Abstract: An efficient, selective and cost-effective procedure has been developed for mono N-arylation of primary alkyl and benzyl carbamates with aryl iodides and bromides by incorporating CuI as an inexpensive and commercially available catalyst. Despite previous reports on C–N coupling reactions, this process does not need expensive ligands and takes advantage of readily available and inexpensive ethylenediamine (EDA) as the ligand. Reaction times were relatively short and related N-arylated carbamates were obtained in excellent yields. Interestingly, replacing CuI with Cu(OAc)2 allowed us to use arylboronic acids as coupling partner for this reaction. All products are well characterized by 1H- and 13C-NMR, MS, melting point, IR and CHNS techniques.
- Sardarian, Ali Reza,DindarlooInaloo, Iman,Zangiabadi, Milad
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p. 642 - 652
(2018/01/11)
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- Ureas as safe carbonyl sources for the synthesis of carbamates with deep eutectic solvents (DESs) as efficient and recyclable solvent/catalyst systems
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A simple, efficient and eco-friendly one-pot synthesis of primary, N-mono- and N-disubstituted carbamates is developed from ureas. The corresponding carbamates were produced at 120 °C, within 18 h, and in the presence of a deep eutectic solvent as a recyclable catalytic system. The catalyst can be reused for several runs without any reduction in its activity. To demonstrate the utility of this approach, a wide variety of alcohols and phenols were studied to find a vast range of carbamate derivatives in moderate to high yields.
- Dindarloo Inaloo, Iman,Majnooni, Sahar
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p. 13249 - 13255
(2018/08/21)
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- Synthesis of Amines, Carbamates and Amides by Multi-Step Continuous Flow Synthesis
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We report the continuous flow synthesis of acyl azides in various continuous flow systems and demonstrate that liquid–liquid separation may be incorporated to prepare anhydrous solutions of the acyl azide, which may be subsequently reacted with appropriate nucleophiles to prepare amines, carbamates and amides within a fully integrated multi-step process in high yields (> 80 %). Interesting effects were also observed when preparing carbamates with long chain alcohols, whereby as the chain length of the alcohol increased the products could be made in high yield even without incorporation of the liquid–liquid separation module.
- Sagandira, Cloudius R.,Watts, Paul
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supporting information
p. 6554 - 6565
(2017/10/09)
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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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- 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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- 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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- 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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- (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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- Fe3O4@SiO2/Schiff base/Pd complex as an efficient heterogeneous and recyclable nanocatalyst for chemoselective: N -arylation of O -alkyl primary carbamates
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An efficient, heterogeneous and cost effective method has been developed using an Fe3O4@SiO2/Schiff base/Pd complex as a magnetic and easily recyclable nanocatalyst for rapid and effective N-arylation of carbamates in good to excellent yield. The catalyst can be easily recovered and reused over six runs without significant decrease in the activity. Further highlights of this protocol are operational simplicity, versatility and relatively short reaction times.
- Sardarian,Zangiabadi,Inaloo, I. Dindarloo
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p. 92057 - 92064
(2016/10/11)
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- One-pot preparation of carbamoyl benzotriazoles and their applications in the preparation of ureas, hydrazinecarboxamides and carbamic esters
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Carbamoyl benzotriazoles were conveniently synthesized in one-pot from carboxylic acids, diphenyl phosphorazidate (DPPA) and 1H-benzotriazole (BtH). The reactivity and applications of carbamoyl benzotriazoles were also explored. Carbamoyl benzotriazoles react smoothly with amino acids, hydrazines and alcohols, thus providing facile access to the corresponding ureas, hydrazinecarboxamides and carbamic esters, respectively, in good to excellent yields.
- Mao, Hui,Liu, Huili,Tu, Yawei,Zhong, Zhiyun,Lv, Xin,Wang, Xiaoxia
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- A synthetic approach to N -aryl carbamates via copper-catalyzed Chan-Lam coupling at room temperature
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A mild and efficient synthesis of N-arylcarbamates was achieved by reacting azidoformates with boronic acids in the presence of 10 mol % of copper chloride catalyst. The reaction proceeds readily in an open flask at room temperature without additional base, ligand, or additive. Rapid access to urea analogues via a two-step one-pot procedure is enabled by reacting N-arylcarbamates with aluminum-amine complexes. In addition, among several boronic acid derivatives prepared, dimethylphenyl boronate was found to react rapidly in its reaction with benzyl azidoformate, invoking in situ generation of this species in the catalytic cycle.
- Moon, Soo-Yeon,Kim, U. Bin,Sung, Dan-Bi,Kim, Won-Suk
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p. 1856 - 1865
(2015/02/19)
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- Metal free oxidative coupling of aryl formamides with alcohols for the synthesis of carbamates
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A direct transformation of N-aryl formamides to the corresponding carbamates via the formation of isocyanate intermediates is achieved in good yields using hypervalent iodine as an oxidant. This journal is
- Reddy, N. Veera,Prasad, K. Rajendra,Reddy, P. Sudhir,Lakshmi Kantam,Reddy, K. Rajender
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supporting information
p. 2172 - 2175
(2014/04/03)
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- Aniline carbamates: A versatile and removable motif for palladium-catalyzed directed c-h activation
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The aniline carbamate is introduced as a new removable directing group for C-H activation. Its versatility and ability as a directing group are demonstrated by its use in the ortho-arylation of a wide variety of aniline derivatives under palladium(II) catalysis, with symmetric diaryliodonium salts as aryl donors. The reaction differs from previously reported arylations in its selectivity and its mechanism, as elucidated by kinetic and isotopic experiments. The directing group can also be easily removed under a variety of conditions.
- Uhlig, Nick,Li, Chao-Jun
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supporting information
p. 12066 - 12070
(2015/03/31)
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- Method for Producing Carbonyl Compund
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A method for producing a carbonyl compound of the present invention comprises a step (X) of reacting a specific compound having a urea bond with a carbonic acid derivative having a carbonyl group (—C(═O)—) under heating at a temperature equal to or higher
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Paragraph 0634-0636
(2013/07/19)
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- Reaction of organozinc halides with aryl isocyanates
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Reformatsky reagent, benzylzinc bromide or alkylzinc iodides react with aryl isocyanates directly to give corresponding N-substituted carbamates under mild reaction conditions. However, the reaction of allylzinc bromide or propargylzinc bromide with aryl isocyanates produces the corresponding N-substituted amides. The reactions provide alternative methods for the synthesis of N-substituted carbamates or amides.
- Yang, Haoran,Huang, Danfeng,Wang, Ke-Hu,Xu, Changming,Niu, Teng,Hu, Yulai
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supporting information
p. 2588 - 2593
(2013/03/28)
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- Synthesis of aryl carbamates via copper-catalyzed coupling of aryl halides with potassium cyanate
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Coupling of aryl halides with potassium cyanate takes place at 100-110 °C in alcohols under the catalysis of CuI (cuprous iodide) and 2-(2,6-dimethylphenylamino)-2-oxoacetic acid, affording the corresponding aryl carbamates with great diversity. Copyright
- Yang, Xinye,Zhang, Yihua,Ma, Dawei
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supporting information
p. 2443 - 2446,4
(2020/08/31)
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- Efficient synthesis of methyl carbamate via Hofmann rearrangement in the presence of TsNBr2
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An efficient method has been developed for the synthesis of carbamates from the corresponding amides via the Hofmann rearrangement using N,N-dibromo-p-toluenesulfonamide (TsNBr2) in the presence of DBU in methanol. The reaction goes into completion in 10-20 min at 65 °C to produce the corresponding carbamate in excellent yield.
- Borah, Arun Jyoti,Phukan, Prodeep
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experimental part
p. 3035 - 3037
(2012/07/27)
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- Computational tools for mechanistic discrimination in the reductive and metathesis coupling reactions mediated by titanium(IV) isopropoxide
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A theoretical study has been carried out at the B3LYP/LANL2DZ level to compare the reactivity of phenyl isocyanate and phenyl isothiocyanate towards titanium(IV) alkoxides. Isocyanates are shown to favour both mono insertion and double insertion reactions. Double insertion in a head-to-tail fashion is shown to be more exothermic than double insertion in a head-to-head fashion. The head-to-head double insertion leads to the metathesis product, a carbodiimide, after the extrusion of carbon dioxide. In the case of phenyl isothiocyanate, calculations favour the formation of only mono insertion products. Formation of a double insertion product is highly unfavourable. Further, these studies indicate that the reverse reaction involving the metathesis of N,N ′-diphenyl carbodiimide with carbon dioxide is likely to proceed more efficiently than the metathesis reaction with carbon disulphide. This is in excellent agreement with experimental results as metathesis with carbon disulphide fails to occur. In a second study, multilayer MM/QM calculations are carried out on intermediates generated from reduction of titanium(IV) alkoxides to investigate the effect of alkoxy bridging on the reactivity of multinuclear Ti species. Bimolecular coupling of imines initiated by Ti(III) species leads to a mixture of diastereomers and not diastereoselective coupling of the imine. However if the reaction is carried out by a trimeric biradical species, diastereoselective coupling of the imine is predicted. The presence of alkoxy bridges greatly favours the formation of the d,l (±) isomer, whereas the intermediate without alkoxy bridges favours the more stable meso isomer. As a bridged trimeric species, stabilized by bridging alkoxy groups, correctly explains the diastereoselective reaction, it is the most likely intermediate in the reaction.
- Kumar, Akshai,Samuelson, Ashoka G
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p. 1343 - 1352
(2013/06/05)
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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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- Metathesis of carbon dioxide and phenyl isocyanate catalysed by group(IV) metal alkoxides: An experimental and computational study
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The insertion reactions of zirconium(IV) n-butoxide and titanium(IV) n-butoxide with a heterocumulene like carbodiimide, carbon dioxide or phenyl isocyanate are compared. Both give an intermediate which carries out metathesis at elevated temperatures by inserting a second heterocumulene in a head-to-head fashion. The intermediate metallacycle extrudes a new heterocumulene, different from the two that have inserted leading to metathesis. As the reaction is reversible, catalytic metathesis is feasible. In stoichiometric reactions heterocumulene insertion, metathesis and metathesis cum insertion products are observed. However, catalytic amounts of the metal alkoxide primarily led to metathesis products. It is shown that zirconium alkoxides promote catalytic metathesis (isocyanates, carbon dioxide) more efficiently than the corresponding titanium alkoxide. The difference in the metathetic activity of these alkoxides has been explained by a computational study using model complexes Ti(OMe) 4 (1bTi) and Zr(OMe)4 (1bZr). The computation was carried out at the B3LYP/LANL2DZ level of theory. Indian Academy of Sciences.
- Kumar, Akshai,Samuelson, Ashoka G
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- Room temperature metathesis of aryl isocyanates and aromatic aldehydes catalyzed by group(IV) metal alkoxides: An experimental and computational study
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Aromatic aldehydes and aryl isocyanates do not react at room temperature. However, we have shown for the first time that in the presence of catalytic amounts of group(IV) n-butoxide, they undergo metathesis at room temperature to produce imines with the extrusion of carbon dioxide. The mechanism of action has been investigated by a study of stoichiometric reactions. The insertion of aryl isocyanates into the metal n-butoxide occurs very rapidly. Reaction of the insertion product with the aldehyde is responsible for the metathesis. Among the n-butoxides of group(IV) metals, Ti(OnBu)4 (8aTi) was found to be more efficient than Zr(OnBu)4 (8aZr) and Hf(OnBu)4 (8aHf) in carrying out metathesis. The surprisingly large difference in the metathetic activity of these alkoxides has been probed computationally using model complexes Ti(OMe)4 (8bTi), Zr(OMe)4 (8bZr) and Hf(OMe)4 (8bHf) at the B3LYP/LANL2DZ level of theory. These studies indicate that the insertion product formed by Zr and Hf are extremely stable compared to that formed by Ti. This makes subsequent reaction of Zr and Hf complexes unfavorable.
- Kumar, Akshai,Samuelson, Ashoka G.
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experimental part
p. 338 - 345
(2010/05/01)
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- CATALYST FOR PRODUCING N-SUBSTITUTED CARBAMATES, AND THE PREPARATION AND APPLICATION OF THE SAME
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The present invention relates to a novel catalyst for producing N-substituted carbamates, the preparation of the catalyst and an improved method for producing N-substituted carbamates from these novel catalysts. The active component of the catalyst is a heteropoly acid and the catalyst support comprises a metal oxide or a metalloid oxide. The catalyst can be used to promote the reaction of carbamate and amine, thereby generating N-substituted carbamates with high yield. In the presence of the catalyst, the reaction conditions are relatively mild, the catalytic activity and selectivity of the reaction are high, and the reaction time is relatively short. Furthermore, the catalyst can be conveniently separated from the reaction system and recycled. therefore, the catalyst can be used to facilitate the further scale-up test and commercial application.
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Page/Page column 8
(2010/12/29)
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- Selenium-catalyzed oxidative carbonylation of aniline and alcohols to n-phenylcarbamates
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A facile one-pot, phosgene-free synthesis of N-phenylcarbamates is demonstrated. Catalyzed by selenium, oxidative carbonylation of aniline with alcohols in the presence of carbon monoxide and oxygen affords the corresponding N-phenylcarbamates, mostly in fair to good yields. Selenium can be easily recovered because of its phase-transfer catalysis function. Copyright
- Zhang, Xiaopeng,Jing, Huanzhi,Zhang, Guisheng
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experimental part
p. 1614 - 1624
(2010/07/09)
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- Process for the preparation of urethanes
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Urethanes are prepared by oxidative carbonylation of at least one amino compound in the presence of carbon monoxide, oxygen and organic, at least one hydroxyl-group-carrying compound. The carbonylation is carried out in the absence of halogen-containing promoters. The carbonylation is also carried out in the presence of a metal complex catalyst which contains neutral bidentate N-chelate ligands of the (N?N) type, two monoanionic N,O-chelate ligands of the general type (N?O)? or tetradentate dianionic chelate ligands (O?N?N?O)2?.
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Page/Page column 13
(2009/12/02)
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- Studies in Acyl C-H activation via aryl and alkyl to acyl "through space" migration of palladium
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Examples of the 1,4-migration of a palladium moiety in aryl- and alkylpalladium intermediates to the acyl position of an aldehyde or formamide have been observed. The resulting acylpalladium intermediate can undergo ester or carbamate formation by reaction with an alcohol; decarbonylation, followed by β hydride elimination to an alkene; reaction with an organomercurial to form an ester; or alkene insertion. Deuterium-labeling studies have been used to confirm the palladium migration mechanism.
- Kesharwani, Tanay,Verma, Akhilesh K.,Emrich, Daniel,Ward, Jeffrey A.,Larock, Richard C.
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supporting information; experimental part
p. 2591 - 2593
(2009/10/23)
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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 3-4
(2008/06/13)
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- Oxidative carbonylation of aniline with new cobalt catalytic systems
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New neutral cobalt(II) complexes containing 2,9-bis(2-hydroxyphenyl)-1,10- phenanthroline and 2,9-bis(2-hydroxyphenyl)-2,2′-bipyridine ligands have been synthesized. These complexes are active catalysts in the oxidative carbonylation of aniline in 1-butanol and NaI as a promoter. The principal products obtained are N,N′-diphenylurea and 1-butyl-N-phenylcarbamate.
- Orejon, Aranzazu,Castellanos, Aida,Salagre, Pilar,Castillon, Sergio,Claver, Carmen
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p. 764 - 768
(2007/10/03)
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- The enhancement of enantioselectivities for lipase-catalyzed reactions by using carbamates
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The enantioselectivity of porcine pancreatic lipase-catalyzed resolution of 1-indanol was enhanced up to 3 fold in the presence of carbamates. The optimum incubation time for 4-nitrophenyl-N-hexyl carbamate and the enzyme was 18 h before this biocatalytic resolution. The optimum concentration of the inhibitor 4-nitrophenyl-N-hexyl carbamate in this resolution was 1% mole equivalent of the substrate 1-indanol.
- Lin, Gialih,Lin, Wen-Yuan,Shieh, Chuen-Tzwu
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p. 8881 - 8884
(2007/10/03)
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- Process for preparing carbonate compounds
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A process for preparing carbonate compounds having the following formula: STR1 wherein R and R' are, the same or different, C1 -C6 alkyl group, a C3 -C6 cycloalkyl group, an optionally substituted C6 -C14 aryl group, an alkylaryl group, or an arylalkyl group is proposed; the process comprises reacting urea or derivatives thereof with appropriate alcohols or phenols and preparing the carbonate compounds via a multiple-step synthesis process.
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- Mechanism of tin(IV) -catalysed urethane formation
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It has been found that dibutyltin dilaurate and dibutyltin dibutanethiolate are almost equally effective as catalysts in the formation of a urethane from phenyl isocyanate and butanol, and that the catalytic activity of both compounds is inhibited by thiols. These results are consistent with a mechanism which involves the N-coordination of the isocyanate with a tin alkoxide that is formed by alcoholysis of the starting tin compound.
- Houghton, Roy P.,Mulvaney, Andrew W.
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- Process for preparing carbonate compounds
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A process for preparing carbonate compounds having the following formula: wherein R and R' are, independently, a C1 - C6 alkyl group, a C3-C6 cycloalkyl group, an optionally substituted C6-C14 aryl group, an alkylaryl group, or an arylalkyl group is proposed; the process comprises preparing the carbonate compounds via a synthesis process comprising the step of, ???(3) allowing the compounds represented by formula [IV] to [VII]: ???wherein R5, R6, R7 and R8 are, independently, hydrogen, a C1-C6 alkyl group, a C1-C6 alkoxyl group, a C1-C6 alkoxy carbonyl group, a substituted or unsubstituted phenyl group; provided that at least one of R5 and R6 is a substituted or unsubstituted phenyl group, and at least one of R7 and R8 is a substituted or unsubstituted phenyl group,???to either each react with itself or to carry out replacement reaction between compounds [IV] and [V], [IV] and [V], [IV] and [VII], [V] and [V], [V] and [VII] or [V] and [VII] in the presence of a catalyst and a temperature from 100 to 300°C to obtain the compounds represented by formula [I].
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- Kinetics and Catalysis of Consecutive Isocyanate Reactions. Formation of Carbamates, Allophanates and Isocyanurates
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Organic isocyanates (I) react with alcohols and phenols (HX) in a sequence of reactions to give carbamates, allophanates and isocyanurates.Rate and equilibrium constants of the individual steps have been determined.The partitioning of the reaction products predominantly depends on the I:HX ratio and the nature of the catalyst applied.At equimolar I:HX ratios, the carbamate is the dominating product in the absence and in the presence of catalysts like tin carboxylates and common tertiary amines including 1,4-diazabicyclooctane (DABCO).In these cases, the rate constant of carbamate formation (k1) is larger than those of allophanate and isocyanurate formation (k2 and k3).With catalysts such as aminals, aminoalcohols, amidines and carboxylate, phenolate and alkoxide anions, however, the isocyanurate is mainly formed.With these catalysts the ratio of rate constants is k1 2 ca. k3.For base catalysts, the k1:k2:k3 ratios depend on the mechanism of catalysis.Tertiary amines react in the alcohol-isocyanate reaction by a concerted termolecular mechanism, whereas the anionic catalysts react by a stepwise mechanism via alcoholate anions.In the reactions of the isocyanate with phenols, carbamates and allophanates, all base catalysts react by the step-wise anionic mechanism, but the anionic ones are more efficient because their conjugate acids form hydrogen-bonded homoassociate complexes in higher extend.At high I:HX ratios, the isocyanurate is the only final product formed via the carbamate and allophanate as detectable intermediates.The kinetics of cyclotrimerisation is mainly governed by the k1:k2:k3 ratios and the magnitude of the equilibrium constants K1, K2 and K3.The kinetic order with respect to isocyanate may vary from 1 to 3.
- Schwetlick, Klaus,Noack, Rainer
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p. 395 - 402
(2007/10/02)
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- Catalysis by μ-Oxo Diiron(III) Complexes of the Methanolysis of Epoxides and the Addition of Alcohols and Thiols to Phenyl Isocyanate
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Carboxylate-bridged μ-oxo diiron(III) complexes of the type 1 very efficiently catalyse (a) the addition of alcohols and thiols to phenyl isocyanate and (b) the ring-opening of epoxides by methanol, with their efficiency being dependent upon the size of the group R.
- Houghton, Roy P.,Rice, Craig R.
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p. 2265 - 2266
(2007/10/02)
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- Carbon Dioxide as a Phosgene Replacement: Synthesis and Mechanistic Studies of Urethanes from Amines, CO2, and Alkyl Chlorides
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Several carbamate esters were synthesized from amines, carbon dioxide, and alkyl chlorides.The effect of added base on the yield and selectivity of carbamate ester formation was found to be highly important with the use of sterically hindered guanidine bases giving the best results.Relative rate studies were carried out giving the following order of reactivity between carbamate anions in acetonitrile with benzyl chloride giving carbamate esters: Et2NCO2(-) = Bu2NCO2(-) > t-BuNHCO2(-) = CyNHCO2(-) = s-BuNHCO2(-) > PhNHCO2(-) > CyCH2NHCO2(-) = n-octylNHCO2(-) = n-BuNHCO2(-).Rate studies were carried out with the diethyl, s-butyl, phenyl, and n-butyl carbamates and activation parameters were determined to be Et2NCO2(-), ΔH(excit.) = 11.8 kcal/mol, ΔS(excit.) = -33 eu; s-BuNHCO2(-), ΔH(excit.) = 12.8 kcal/mol, ΔS(excit.) = -33 eu; PhNHCO2(-), ΔH(excit.) = 14.3 kcal/mol, ΔS(excit.) = -28 eu; n-BuNHCO2(-), ΔH(excit.) = 23.4 kcal/mol, ΔS(excit.) = -3 eu.The unusual results obtained from the use of n-BuNHCO2(-) prompted further studies which showed that the rate of the reaction was inversely dependent on carbon dioxide pressure (20 psig CO2, k = 4.84E-4 M-1 s-1; 120 psig CO2, k = 1.83E-4 M-1 s-1).Nitrogen NMR spectroscopy indicated, via a labeling study with 15N amines and 13C enriched carbon dioxide, the formation of doubly inserted product from the addition of two carbon dioxides to ethylamine in acetonitrile.
- McGhee, William,Riley, Dennis,Christ, Kevin,Pan, Yi,Parnas, Barry
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p. 2820 - 2830
(2007/10/02)
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- α-Haloalkyl haloformates and related compounds. 2. Synthesis of dichloromethyl carbonates and their transformation to carbamates
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Dichloromethyl carbonates, easily available upon treatment alcohols with dichloromethyl chloroformate, react with various amines to give carbamates in high yield under mild conditions. Extension of the reaction for the synthesis of oxazolones from 2-aminoalcohols is also demonstrated.
- Patonay,Hegedus,Mogyorodi,Zolnai
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p. 2507 - 2513
(2007/10/02)
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- Three Fundamental Mechanisms of Base-catalysed Reactions of Isocyanates with Hydrogen-acidic Compounds
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The base-catalysed addition of H-acidic compounds HX, such as alcohols, phenols and amines, to isocyanates giving carbamates and ureas may proceed by three fundamental mechanisms depending on the acidity and nucleophilicity of the particular HX and the ba
- Schwetlick, Klaus,Noack, Rainer,Stebner, Fanziska
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p. 599 - 608
(2007/10/02)
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