- Enzyme-Inspired Lysine-Modified Carbon Quantum Dots Performing Carbonylation Using Urea and a Cascade Reaction for Synthesizing 2-Benzoxazolinone
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Catalysts as the dynamo of chemical reactions along with solvents play paramount roles in organic transformations in long-lasting modes. Thus, developing effective and biobased catalysts in nontoxic solvents is highly in demand. In this report, carbon quantum dots (CQDs) functionalized with-lysine (Lys-CQDs) were generated from entirely nature-derived materials; they were demonstrated to be a promising catalyst for C-N bond formation in choline chloride urea (ChCl/U), a natural deep eutectic solvent (NADES). Among a number of synthesized CQDs, Lys-CQD turned out to be a powerful catalyst in the model reaction with aniline to afford phenyl urea. This type of transformation is important because aniline as a nucleophile has low activity, and urea is a very weak electrophile but an abundant natural source of the carbonyl moiety at the same time. The optimized reaction was performed under a highly desirable condition without using tedious and toxic workup processes at a low temperature (37 °C for aliphatic amines and 60 °C for aniline derivatives), as well as by embracing the broad scope of products in good to high yields even with weak nucleophiles such as aniline. A proposed acid-activated mechanism was suggested for the model reaction that was further confirmed by detecting ammonia as the leaving group. To show further multifunctionality of the catalyst, a cascade catalysis approach was developed for synthesizing 2-benzoxazolinone, which was furnished in a two-step transformation, starting from 2-aminophenol. Using X-ray crystallography, the structure of the final product in the cascade reaction was also determined. The catalyst was characterized using various analytical techniques including SEM, TEM, AFM, XRD, IR spectroscopy, UV-vis spectroscopy, DLS, and fluorescence spectroscopy. Measuring the acid/base sites by back titration, the catalyst was shown to be highly functionalized by the lysine functional group. The size of the catalyst was determined to be in the range of 1-8 nm, having a well-dispersed surface. In all, Lys-modified CQD, as a metal-free catalyst, was synthesized, characterized, and optimized for carbonylation, as well as a cascade reaction, under mild conditions. The whole process including catalyst synthesis and organic transformations is economically competitive and fulfills all requirements toward viability.
- Hasani, Morteza,Kalhor, Hamid R.
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p. 10778 - 10788
(2021/09/08)
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- A Straightforward Synthesis of N-Substituted Ureas from Primary Amides
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A direct and convenient method for the preparation of N-substituted ureas is achieved by treating primary amides with phenyliodine diacetate (PIDA) in the presence of an ammonia source (NH 3 or ammonium carbamate) in MeOH. The use of 2,2,2-trifluoroethanol (TFE) as the solvent increases the electrophilicity of the hypervalent iodine species and allows the synthesis of electron-poor carboxamides. This transformation involves a nucleophilic addition of ammonia on the isocyanate intermediate generated in situ by a Hofmann rearrangement of the starting amide.
- Franck, Xavier,Glachet, Thomas,Ibert, Quentin,Lohier, Jean-Fran?ois,Reboul, Vincent,Saraiva Rosa, Nathalie
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p. 2099 - 2105
(2020/07/13)
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- A green and facile approach for the synthesis of N-monosubstituted ureas in water: Pd catalyzed reaction of arylcyanamides (an unexpected behavior of electron withdrawing groups)
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The Fe3O4 magnetic nano-particles were prepared, coated with tetraethyl orthosilicate (TEOS), functionalized with 3-chloropropyltrimethoxysilane (CPTMS), further functionalized with 2,2′-(piperazine-1,4-diylbis(methylene) dianiline (PDMD) and the corresponding Pd complex synthesized as a novel nano-magnetic heterogeneous catalyst (Fe3O4@SiO2@CPTMS@PDMD@Pd) to be used for the synthesis of various N-monosubstituted ureas in water. Also, in another attempt to see the effect of HCOOH, the hydration reaction of arylcyanamide was carried out in the presence of HCOOH (water + 98% HCOOH) which had two effects: it decreased the amount of the Pd catalyst from 40 to 30 mg, and the reaction condition was changed from the reflux condition to room temperature. Interestingly, the arylcyanamides with electron withdrawing groups influence the course of the reaction and need more reaction times for completion which is an unexpected behavior, probably due to the high electron density around the central carbon atom of the nitrile group.
- Habibi, Davood,Heydari, Somayyeh,Faraji, Alireza,Keypour, Hasan,Mahmoudabadi, Masoumeh
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p. 520 - 529
(2018/06/26)
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- Synthesis and crystal structure of N-(3-benzylamino-2-cyano-3- methylthioacrylyl)-N′-(substituted phenyl)ureas
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Phenylurea groups were introduced into the frame of traditional cyanoacrylate and a series of N-(3-benzylamino-2-cyano-3-methylthioacrylyl)- N′-(substituted phenyl)ureas were synthesized. All compounds are new and their structures were confirmed by 1H NMR, 13C NMR and mass spectral analyses.
- Zhong, Shi Hua,Fan, Ming Liang,Liu, Bing Yu,Wei, Dong Mei,Liu, Jian Bing
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p. 295 - 300
(2013/07/27)
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- Synthesis and anticonvulsant activity of halo-substituted aryl urea and thioureas
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Halo-substituted arylureas have been prepared by condensation of halo-substituted primary arylamine with sodium cyanate and halo-substituted arylthioureas have been prepared by condensation of halo-substituted primary arylamine with ammonium thiocyanate in presence of acid. The structures of compounds synthesized have been confirmed by elemental analysis and spectral data. Their anticonvulsant activity was evaluated, p-bromophenyl urea and p-chlorophenyl and p-bromophenyl thioureas were found to be most active in the maximal electro shock (MES) test. p-Bromophenyl derivatives were found least neurotoxic in the rotorod test. The results were compared with standard drug phenytoin.
- Gupta, Mahesh Kumar,Pandeya, Suerendra N.,Zaiad, Golal M.,Gangwar
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experimental part
p. 1421 - 1424
(2011/09/20)
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- Oxidation of arylthiourea by cetyltrimethylammonium dichromate
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With a view to investigate the oxidation behaviors of cetyltrimethylammonium dichromate on multifunctional groups, some arylthioureas were subjected to oxidation, both in neutral and in acidic conditions. In neutral conditions, the products were found to be a mixture of corresponding urea and isonitrile. In acidic conditions, the products were corresponding ureas only. A probable mechanism was proposed for the formation of the product, wherein the first step involves coupling of-NH2 and-SH of one molecule to the-NH2 and-SH of another molecule, respectively, which is followed by removal of nitrogen and sulfur. The microwave irradiation resulted in great yield of isonitrile than urea in neutral conditions. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications to view the free supplemental file. Copyright Taylor & Francis Group, LLC.
- Sahu, Sandhyamayee,Sahoo, Prangya Rani,Patel, Sabita,Mishra
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experimental part
p. 3268 - 3273
(2010/12/24)
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- Oxidation kinetics of arylthioureas by cetyltrimethylammonium dichromate
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Arylthioureas, which are toxic, on oxidation by cetyltrimethylammonium dichromate in acetic acid undergo desulphurization to the corresponding non-toxic arylureas. The mechanism of the oxidation reaction has been studied spectrophotometrically. The rate of reaction is found to be dependent on [CTADC], [phenylthiourea], [acid], [surfactant], polarity of the solvents and reaction temperature. The reaction is fractional order with respect to [substrate] and is catalyzed by acid. With increase in [CTADC], the rate constant decreases. The structure of the substituents has no significant effect on the rate constant. On the basis of various observations, a mechanism has been proposed for the oxidation reaction.
- Sahoo, Prangya Rani,Sahu, Sandhyamayee,Patel, Sabita,Mishra
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scheme or table
p. 1483 - 1487
(2011/02/28)
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- Phenylureas. Part 1. Mechanism of the basic hydrolysis of phenylureas
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The mechanism of the hydrolytic decomposition of phenylureas in basic media in the pH range 12 to 14 is investigated. In this pH range a levelling of the rate-pH curve is observed as well as a change of the substituent influence on the hydrolysis rate. These experimental findings suggest the formation of an unreactive side product of the phenylurea in a parasitic side equilibrium at sufficiently high pH. The urea dissociates at the aryl-NH group to give its conjugate base. For the hydrolytic decomposition of phenylureas an addition-elimination mechanism is proposed as has been established for the alkaline hydrolysis of carboxylic acid esters and amides.
- Laudien,Mitzner
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p. 2226 - 2229
(2007/10/03)
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- KINETICS AND MECHANISM OF METHANOLYSIS OF BENZOYL DERIVATIVES OF SUBSTITUTED PHENYLUREAS AND PHENYLTHIOUREAS
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The methanolysis rate constants and dissociation constants have been measured of benzoyl derivatives of substituted phenylureas and phenylthioureas.The dissociation constants of the thio derivatives are higher by 1 order of magnitude and the rate constants are higher by 2 orders of magnitude than the respective values of the oxygen analogues.Logarithms of the rate and dissociation constants have been correlated with Hammett ? constant; the ρ constant of the methanolysis of the oxygen derivatives is almost 2 * higher than that of the thio derivatives, which is explained by a change in the rate-limiting step.Methylation of the phenyl nitrogen atom increases the acidity by almost 2 orders of magnitude.This effect is due obviously to steric hindrance to the conjugation with the adjacent carbonyl or thiocarbonyl group.
- Kavalek, Jaromir,El Bahaie, Said,Sterba, Vojeslav
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p. 2103 - 2110
(2007/10/02)
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- 3-(1-Hydroxyalkyl)-1,4,2-dioxazol-5-ones and 3-Hydroxyoxazolidine-2,4-diones from 2-Hydroxycarbohydroxamic Acids and 1,1'-Carbonyldiimidazole
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The reaction of 2-hydroxycarbohydroxamic acids 6 with 1,1'-carbonyldiimidazole produces 3-(1-hydroxyalkyl)-1,4,2-dioxazol-5-ones 7 and 3-hydroxyoxazolidine-2,4-diones 8.The formation of the heterocycles 7 and 8 depends largely on the substitution at C-2 of 6.Excess of imidazole causes rapid decomposition of 7 into carbonyl compound 9 and isocyanic acid, which yields the adduct 10 with imidazole.Benzylaminolysis of 7a gives 11 whereas the reaction of 7a with 3-chloroaniline produces the ureas 12 and 14 and benzophenone (9a).From the reaction of 7a with imidazole in a mole ratio of 1 : 1 the decomposition products 9a and 10 and 3-hydroxy-5,5-diphenyloxazolidine-2,4-dione (8a) are obtained.
- Geffken, Detlef
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p. 211 - 218
(2007/10/02)
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