- P(III)-Assisted Electrochemical Access to Ureas via in situ Generation of Isocyanates from Hydroxamic Acids
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An external oxidant-free protocol for the generation of isocyanates from hydroxamic acids assisted by trivalent phosphine under mild electrochemical conditions was reported. The process started with the anodic oxidation of hydroxamic acids, followed by reacting with phosphine to form corresponding alkoxyphosphoniums and subsequent rearrangement with the release of tri-substituted phosphine oxide as the driving force to give isocyanates, which were trapped by N-based nucleophiles to produce various ureas. This method provides a broadly applicable procedure to access isocyanate intermediates under mild electrochemical conditions.
- Meng, Haiwen,Sun, Kunhui,Xu, Zhimin,Tian, Lifang,Wang, Yahui
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supporting information
p. 1768 - 1772
(2021/03/26)
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- METHOD OF CONVERTING CARBON DIOXIDE INTO CARBONYL COMPOUNDS
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The present invention provides a method for fixing carbon dioxide gas as a carbonyl compound represented by formula (3) as depicted by Figure 1 and comprising, purging of carbon dioxide in a solution of a nucleophile represented by the formula (1) in presence of a solvent at a temperature ranging from -40 Degree Celsius to 35 Degree Celsius, followed by adding a reagent at temperature ranging from -40 degree to 35 degree and thereafter adding another nucleophile represented by the formula (2) to obtain carbonyl compound represented by formula (3). The present invention can be advantageously used to obtain commercially important carbonyl compounds and clean unwanted carbon dioxide gas from the atmosphere and industrial effluents.
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Page/Page column 14
(2019/05/02)
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- CaI2-Catalyzed direct transformation of: N -Alloc-, N -Troc-, and N -Cbz-protected amines to asymmetrical ureas
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A novel and facile CaI2-catalyzed direct synthesis of asymmetrical ureas from N-Alloc-, N-Troc-, and N-Cbz-protected amines is developed. In this study, the efficient reaction of Alloc-, Troc-, and Cbz-carbamates with amines in the presence of catalytic CaI2 successfully generated various asymmetrical ureas. This catalytic synthetic procedure provided the desired ureas via reactions of these protected aromatic and aliphatic amines with various amines in high yields without side products. This suggests that novel direct synthesis of ureas from Alloc-, Troc-, and Cbz-carbamates can be a promising approach for the synthesis of useful ureas.
- Tran, Van Hieu,Kim, Hee-Kwon
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p. 14093 - 14101
(2019/09/18)
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- Chemoselective isocyanide insertion into the N-H bond using iodine-DMSO: Metal-free access to substituted ureas
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Insertion of isocyanides into the N-H bond gives access to many medicinally important and structurally diverse complex nitrogen-containing heterocycles. Although the transition metal catalyzed isocyanide insertion into the N-H bond is very common, polymerization of isocyanides in the presence of a transition metal and their strong coordination with metals are the common drawbacks. On the other hand, the inertness of most of the isocyanides towards amines in the absence of a metal catalyst has stymied the growth of the metal-free approach for isocyanide insertion into amines. As a result, only a handful of metal catalysed methods with limited substrate scopes have been reported for the synthesis of ureas via isocyanide insertion into amines and no metal-free version has been reported yet. Interestingly, chemoselective isocyanide insertion into amines has not been reported in the literature. We employed the I2-DMSO reagent system for the chemoselective synthesis of ureas, where isocyanides react with aliphatic amines only, while aromatic amines need a nucleophilic activator (DABCO) to facilitate the formation of ureas. This method gave direct and chemoselective access to ureas by evading the commonly used yet toxic isocyanates.
- Bora, Porag,Bez, Ghanashyam
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supporting information
p. 8363 - 8366
(2018/08/03)
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- Facile direct synthesis of unsymmetrical ureas from N-Alloc-, N-Cbz-, and N-Boc-protected amines using DABAL-Me3
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A practical synthetic method for the direct synthesis of unsymmetrically substituted ureas from N-Alloc-, N-Cbz-, and N-Boc-protected amines is described. In this study, efficient direct conversion of the Alloc-, Cbz-, and Boc-carbamate compounds to ureas was achieved in the presence of DABAL-Me3, an air stable and easily handled reagent. Using this reaction method, both protected aromatic and aliphatic amines were successfully transformed into various trisubstituted and tetrasubstituted ureas with high yields without side product. Our findings offer promising guidelines for direct preparation of useful ureas from N-Alloc-, N-Cbz-, and N-Boc-carbamates.
- Kang, Soosung,Kim, Hee-Kwon
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p. 4036 - 4046
(2018/06/13)
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- Synthesis of 11C-labelled ureas by palladium(II)-mediated oxidative carbonylation
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Positron emission tomography is an imaging technique with applications in clinical settings as well as in basic research for the study of biological processes. A PET tracer, a biologically active molecule where a positron-emitting radioisotope such as carbon-11 has been incorporated, is used for the studies. Development of robust methods for incorporation of the radioisotope is therefore of the utmost importance. The urea functional group is present in many biologically active compounds and is thus an attractive target for incorporation of carbon-11 in the form of [11C]carbon monoxide. Starting with amines and [11C]carbon monoxide, both symmetrical and unsymmetrical 11C-labelled ureas were synthesised via a palladium(II)-mediated oxidative carbonylation and obtained in decay-corrected radiochemical yields up to 65%. The added advantage of using [11C]carbon monoxide was shown by the molar activity obtained for an inhibitor of soluble epoxide hydrolase (247 GBq/μmol-319 GBq/μ mol). DFT calculations were found to support a reaction mechanism proceeding through an 11C-labelled isocyanate intermediate.
- Roslin, Sara,Brandt, Peter,Nordeman, Patrik,Larhed, Mats,Odell, Luke R.,Erikssoni, Jonas
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- Preparation method for alkyl/benzyl/aryl urea compounds through heterogeneous-phase catalysis
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The invention discloses a preparation method for formula (I) compounds, and the compounds are obtained by reacting a formula (II) compound with a formula (III) compound in a solvent in carbon monoxide atmosphere under catalysis of a heterogeneous-phase pa
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Paragraph 0063-0071; 0072; 0073; 0074; 0076; 0078; 0084
(2016/10/09)
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- A facile method for the preparation of unsymmetrical ureas utilizing zirconium (IV) chloride
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A facile synthetic method for the preparation of unsymmetrical ureas from amines is described. Carbamoyl imidazole compounds were prepared by the reaction of 1, 1-carbonyldiimidazole with primary or secondary amines, and further activation by treatment with zirconium(IV) chloride to generate the desired urea. This reaction protocol was applied to the synthesis of tri and tetrasubstituted ureas with high yields. This study provides an alternative guideline for the practical preparation of various unsymmetrical ureas.
- Lee, Anna,Kim, Hee-Kwon,Thompson, David H.
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p. 154 - 160
(2016/02/26)
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- One-pot synthesis of ureas from Boc-protected amines
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A practical one-pot synthesis of ureas is described. Boc-protected amines can be transformed into nonsymmetrical and symmetrical disubstituted and trisubstituted ureas utilizing 2-chloropyridine and trifluoromethanesulfonyl anhydride for the in situ generation of an isocyanate, which reacts with an amine. A variety of amines can be employed successfully, leading to high yields of isolated ureas.
- Spyropoulos, Constantinos,Kokotos, Christoforos G.
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p. 4477 - 4483
(2014/06/09)
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- Transamidation of carboxamides catalyzed by Fe(III) and water
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The highly efficient transamidation of several primary, secondary, and tertiary amides with aliphatic and aromatic amines (primary and secondary) is described. The reaction is performed in the presence of a 5 mol % concentration of different hydrated salts of Fe(III), and the results show that the presence of water is crucial. The methodology was also applied to urea and phthalimide to demonstrate its versatility and wide substrate scope. An example of its use is an intramolecular application in the synthesis of 2,3-dihydro-5H-benzo[b]-1,4- thiazepin-4-one, which is the bicyclic core of diltiazem and structurally related drugs (Budriesi, R.; Cosimelli, B.; Ioan, P.; Carosati, E.; Ugenti, M. P.; Spisani, R. Curr. Med. Chem. 2007, 14, 279-287). A plausible mechanism that explains the role of water is proposed on the basis of experimental observations and previous mechanistic suggestions for transamidation reactions catalyzed by transition metals such as copper and aluminum. This methodology represents a significant improvement over other existing methods; it can be performed in air and with wet or technical grade solvents.
- Becerra-Figueroa, Liliana,Ojeda-Porras, Andrea,Gamba-Sánchez, Diego
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p. 4544 - 4552
(2014/06/09)
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- Palladium-mediated oxidative carbonylation reactions for the synthesis of 11C-radiolabelled ureas
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Palladium(II)-mediated oxidative carbonylation reactions have been used to synthesize 11C-radiolabelled ureas via the coupling of amines with [11C]carbon monoxide, in a one-pot process. Following trapping of 11CO in a solution of copper(I) tris(3,5-dimethylpyrazolyl)borate, homocoupling reactions of primary aliphatic amines proceed in the presence of Pd(PPh3)2Cl2 to give the corresponding N,N-disubstituted [11C]ureas. Secondary amines do not produce the corresponding N,N,N,N-tetrasubsituted [11C]ureas under these conditions. This difference in reactivity allows for the formation of unsymmetrical N,N',N'-trisubstituted [11C]ureas using a mixture of a primary amine and a reactive secondary amine. The potential use of this method in positron emission tomography (PET) was demonstrated by the synthesis of the M1 muscarinic acetylcholine receptor radiotracer, [11C-carbonyl] GSK1034702.
- Kealey, Steven,Husbands, Stephen M.,Bennacef, Idriss,Gee, Antony D.,Passchier, Jan
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p. 202 - 208
(2014/05/06)
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- Iron(III) catalysed synthesis of unsymmetrical di and trisubstituted ureas - A variation of classical Ritter reaction
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An application of the classical Ritter reaction for the synthesis of unsymmetrical di and trisubstituted ureas catalyzed by FeCl3 is described. The protocol is of significant interest in view of the easy availability of precursors, mild reaction conditions employed and interestingly its applicability for the alkylation of alcohols capable of forming stable carbocationic intermediates even to the sterically hindered moieties. The Royal Society of Chemistry 2012.
- Basavaprabhu, Hosamani,Sureshbabu, Vommina V.
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supporting information; experimental part
p. 2528 - 2533
(2012/04/23)
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- Straightforward carbamoylation of nucleophilic compounds employing organic azides, phosphines, and aqueous trialkylammonium hydrogen carbonate
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In the presence of aqueous trialkylammonium hydrogen carbonate, the Staudinger reaction leads to the intermediate formation of the corresponding isocyanate, which, in turn, reacts further with a nucleophilic reagent also present in the mixture and results in carbamoylation with good yield. On the basis of this reaction a practical carbamoylation procedure was devised and a comparative study on suitability of different solvents and phosphorus (III) derivatives for carbamoylation reaction was conducted. The versatility of the method was demonstrated by examples with different classes of nucleophilic compounds that included the aminomethyl resin and natural compounds that display poor solubility in organic solvents.
- Yagodkin, Andrey,L?schcke, Kerstin,Weisell, Janne,Azhayev, Alex
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experimental part
p. 2210 - 2221
(2010/04/29)
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- Pd(OAc)2-catalyzed carbonylation of amines
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A phosphine-free catalytic system [Pd(OAc)2-Cu(OAc) 2-air] induced a substrate-specific carbonylation of amines in boiling toluene under CO gas (1 atm). Symmetrical N,N′-dialkylureas were obtained by the carbonylation of primary amines. N,N,N′-Trialkylureas were selectively formed by addition of a secondary amine to the above reaction vessel. Secondary amines did not give tetraalkylureas. However, dialkylamines with a phenyl group on their alkyl chains, such as N-monoalkylated benzylic amine or phenethylamine derivatives, underwent a direct aromatic carbonylation to afford five- or six-membered benzolactams. In the carbonylation, the chelation effect or steric repulsion between Pd(II) and the meta-substituent in the ortho-palladation and the ring sizes of cyclopalladation products that were formed prior to carbonylation were found to generate good site selectivity and increase the reaction rate. In contrast, carbonylation of ω- arylalkylamines with a hydroxyl group gave neither ureas nor benzolactams but instead produced 1,3-oxazolidinones smoothly. Hydrochlorides of amines also underwent carbonylation to afford the corresponding amides under the conditions used. This procedure made it possible to prepare ureas of amino acid esters and N-alkylcarbamates in practical yields.
- Orito, Kazuhiko,Miyazawa, Mamoru,Nakamura, Takatoshi,Horibata, Akiyoshi,Ushito, Harumi,Nagasaki, Hideo,Yuguchi, Motoki,Yamashita, Satoshi,Yamazaki, Tetsuro,Tokuda, Masao
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p. 5951 - 5958
(2007/10/03)
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- Self-indicating amine scavenger resins
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Self-indicating methylisocyanate resin, which functions as both a scavenger and an indicator for amines, was used for in-situ reaction monitoring and purification of a urea based library.
- Cho, Jin Ku,White, Peter D.,Klute, Wolfgang,Dean, Tony W.,Bradley, Mark
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p. 502 - 503
(2007/10/03)
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- The direct conversion of carbamates to ureas using aluminum amides
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The conversion of carbamates into ureas using aluminum amide complexes is reported. This reaction is a convenient method to prepare bi-, tri- and tetra-substituted ureas from carbamate-protected primary or secondary amines by reaction with primary or secondary amines in the presence of stoichometric quantities of trimethylaluminum. A reactivity trend of the various carbamates was observed and methyl and benzyl carbamates were reacted selectively in the presence of t-butyl carbamates.
- Lee, Sang-Hyuep,Matsushita, Hana,Clapham, Bruce,Janda, Kim D.
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p. 3439 - 3443
(2007/10/03)
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- A simple conversion of amines into monosubstituted ureas in organic and aqueous solvents
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A versatile and highly efficient synthesis of monosubstituted ureas is described. The reaction of an amine with 4-nitrophenyl-N-benzylcarbamate, followed by hydrogenolysis, provides the corresponding urea in high yield and purity. This carbamate can also be employed for the derivatization of water-soluble polyamines (e.g. aminoglycoside antibiotics), while other reagents (e.g. benzylisocyanate) fail to give the desired products in any significant yield.
- Liu, Qi,Luedtke, Nathan W.,Tor, Yitzhak
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p. 1445 - 1447
(2007/10/03)
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- sYNTHESIS OF N,N'-DISUBSTITUTED UREAS FROM CARBAMATES
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A simple synthesis of N,N'-disubstituted ureas from carbamates is described involving displacement of an alkoxy group by the magnesium salt of an amine generated in situ by treatment with ethylmagnesium bromide.
- Basha, Anwer
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p. 2525 - 2526
(2007/10/02)
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- Cyclic esters of 3,4-dihydroxy-thiophene-1,1-dioxide compounds and 3,4-dihydroxy-cyclopentadienone compounds
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Cyclic esters of 3,4-dihydroxy-thiophene-1,1-dioxide and of the corresponding cyclopentadienone compound, and their manufacture. The compounds can be used as "solid forms" of phosgene, thiophosgene or oxalyl chloride, or as acyl transfer agents.
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