- 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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- One-Pot Synthesis of N-Monosubstituted Ureas from Nitriles via Tiemann Rearrangement
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Amidoximes, obtained from the reaction of nitriles with hydroxylamine, underwent Tiemann rearrangement in the presence of benzenesulfonyl chlorides (TsCl or o-NsCl) to form the N-substituted cyanamides. Subsequently, acidic hydrolysis of the cyanamides afforded the corresponding N-monosubstituted ureas. The synthesis of N-monosubstituted ureas from nitriles was accomplished by three steps in one pot, which provides a direct access to versatile N-monosubstituted urea derivatives from a wide variety of nitriles.
- Wang, Chien-Hong,Hsieh, Tsung-Han,Lin, Chia-Chi,Yeh, Wen-Hsiung,Lin, Chih-An,Chien, Tun-Cheng
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supporting information
p. 1823 - 1826
(2015/08/06)
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- Synthesis of unsymmetrical diarylureas via Pd-catalyzed C-N cross-coupling reactions
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A facile synthesis of unsymmetrical N,N′-diarylureas is described. The utilization of the Pd-catalyzed arylation of ureas enables the synthesis of an array of diarylureas in good to excellent yields from benzylurea via a one-pot arylation-deprotection protocol, followed by a second arylation.
- Breitler, Simon,Oldenhuis, Nathan J.,Fors, Brett P.,Buchwald, Stephen L.
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p. 3262 - 3265
(2011/08/07)
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- Cyclic ureas as ortho directing substituents
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Six-membered cyclic ureas are shown to have a weak ortho directing ability when linked through nitrogen to benzene and pyridine rings.
- Meigh,Alvarez,Joule
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p. 2012 - 2021
(2007/10/03)
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- Central Nervous System Active Compounds. XIV On the Cyclization of N-Acyl-N'-arylureas
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The cyclization of N-acyl-N'-arylureas in polyphosphoric acid has been reinvestigated.The product is not only the 4-substituted quinazolin-2(1H)-one as reported, but also contains the 2-acylaniline in major proportions.Two minor products have also been isolated.At 80 deg, an intermediate has been detected, the properties of which are consistent with it being the corresponding 2-acylphenylurea.Acyl ureas with strongly electron-withdrawing acyl groups from major amount of the corresponding anilide by the formal loss of cyanic acid.The application of this reaction tothe synthesis of quinazolinylphthalides has been investigated.
- Heinicke, Grant,Hung, Tran V.,Prager, Rolf H.,Ward, A. David
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p. 831 - 844
(2007/10/02)
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