- 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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- Catalytic hydration of cyanamides with phosphinous acid-based ruthenium(ii) and osmium(ii) complexes: scope and mechanistic insights
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The synthesis of a large variety of ureas R1R2NC(O)NH2 (R1 and R2 = alkyl, aryl or H; 26 examples) was successfully accomplished by hydration of the corresponding cyanamides R1R2NCN using the phosphinous acid-based complexes [MCl2(η6-p-cymene)(PMe2OH)] (M = Ru (1), Os (2)) as catalysts. The reactions proceeded cleanly under mild conditions (40-70 °C), in the absence of any additive, employing low metal loadings (1 molpercent) and water as the sole solvent. In almost all the cases, the osmium complex 2 featured a superior reactivity in comparison to that of its ruthenium counterpart 1. In addition, for both catalysts, the reaction rates observed for the hydration of the cyanamide substrates were remarkably faster than those involving classical aliphatic and aromatic nitriles. Computational studies allowed us to rationalize all these trends. Thus, the calculations indicated that the presence of a nitrogen atom directly linked to the CN bond depopulates electronically the nitrile carbon by inductive effect when coordinated to the metal center, thus favouring the intramolecular nucleophilic attack of the OH group of the phosphinous acid ligand to this carbon. On the other hand, the higher reactivity of Os vs. Ru seems to be related with the lower ring strain on the incipient metallacycle that starts to form in the transition state associated with this key step in the catalytic cycle. Indirect experimental evidence of the generation of the metallacyclic intermediates was obtained by studying the reactivity of [RuCl2(η6-p-cymene)(PMe2OH)] (1) towards dimethylcyanamide in methanol and ethanol. The reactions afforded compounds [RuCl(η6-p-cymene)(PMe2OR)(NCNMe2)][SbF6] (R = Me (5a), Et (5b)), resulting from the alcoholysis of the metallacycle, which could be characterized by single-crystal X-ray diffraction. This journal is
- álvarez, Daniel,Cadierno, Victorio,Crochet, Pascale,González-Fernández, Rebeca,López, Ramón,Menéndez, M. Isabel
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p. 4084 - 4098
(2020/07/09)
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- A practically simple, catalyst free and scalable synthesis of: N -substituted ureas in water
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A practically simple, mild and efficient method is developed for the synthesis of N-substituted ureas by nucleophilic addition of amines to potassium isocyanate in water without organic co-solvent. Using this methodology, a variety of N-substituted ureas (mono-, di- and cyclic-) were synthesized in good to excellent yields with high chemical purity by applying simple filtration or routine extraction procedures avoiding silica gel purification. The developed methodology was also found to be suitable for gram scale synthesis of molecules having commercial application in large volumes. The identified reaction conditions were found to promote a unique substrate selectivity from a mixture of two amines.
- Tiwari, Lata,Kumar, Varun,Kumar, Bhuvesh,Mahajan, Dinesh
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p. 21585 - 21595
(2018/06/26)
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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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- IL-8 RECEPTOR ANTAGONISTS
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The present invention relates to novel compounds and a novel use of phenyl ureas in the treatment of disease states mediated by the chemokine Interleukin-8 (IL-8).
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- Synthesis of a Triazolophenanthridine via Photocyclisation of 3,4-Diaryl-5-hydroxy-Δ2-1,2,4,-triazoles
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The oxidative eliminative 1,6-photocyclisation of 4,5-diphenyl-3-hydroxy-Δ2-1,2,4-triazole (1a) and derivatives containing bromine in ortho-position in either of the two phenyl groups (1b and 1c) gives the s-triazolophenanthridine (5).Co
- Rama Devi, M.,Pandey, G.,Madhusudana Rao, Jampani,Srinivasan, V. R.
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p. 606 - 609
(2007/10/02)
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