- Isocyanate diinsertion into the N-H bond of the 2-pyridylamino ligand of organolanthanides
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[Cp2LnNHPy]2 (Py = 2-pyridyl) (1a-e) react with phenyl isocyanate to form the N-H diinsertion products Cp2Ln [η2:η1-PyNCON(Ph)CONHPh](THF) (Ln = Yb (3a), Er (3b), Y (3c), Dy (3d), Gd (3e)). It has been proven that n Pr 2NH can abstract one PhNCO unit from 3c to form Cp2 Y[η3-OC(NHPh)NPy] (2c) and nPr2 NHCONHPh (4), representing a rare example of selective release of a functional group of ligands in organolanthanide chemistry. Hydrolysis of 2c gives the organic nitrogen-containing product PyNHCONHPh (5). Moreover, 3c can also be obtained by the reaction of 2c with PhNCO. These results demonstrate that the diinsertion of PhNCO into the N-H bond of coordinated amino ligands might proceed in a stepwise manner. All the compounds were characterized by elemental analysis and spectroscopic properties. The structures of compounds 3a-e and 4 are also determined through X-ray single-crystal diffraction analysis. The Royal Society of Chemistry 2010.
- Sun, Yan,Zhang, Zhengxing,Wang, Xu,Li, Xiaoqing,Weng, Linhong,Zhou, Xigeng
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- 2,2,2-Trifluroenthanol promoted synthesis of unsymmetrical ureas from dioxazolones and amines via tandem lossen rearrangement/condensation process
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A 2,2,2-trifluroenthanol (TFE) promoted synthesis of unsymmetric ureas was described. This approach enabled the construction of a variety of ureas from the readily prepared and easy-to-handle dioxazolones and amines via tandem Lossen rearrangement/condensation process. The reaction featured mild conditions for the urea synthesis under metal-free conditions, which was successively applied in the scale-up synthesis of herbicides Monuro and Isoproturon.
- Li, Jian,He, Wang,Lei, Pan,Song, Jiacheng,Huo, Jiyou,Wei, Hongbo,Bai, Hongjin,Xie, Weiqing
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supporting information
p. 3590 - 3600
(2021/10/07)
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- Lanthanum(III) Trifluoromethanesulfonate Catalyzed Direct Synthesis of Ureas from N-Benzyloxycarbonyl-, N -Allyloxycarbonyl-, and N -2,2,2-Trichloroethoxycarbonyl-Protected Amines
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A novel lanthanum triflate mediated conversion of N -benzyloxycarbonyl-, N -allyloxycarbonyl-, and N -trichloroethoxycarbonyl-protected amines into nonsymmetric ureas was discovered. In this study, lanthanum triflate was found to be an effective catalyst for preparing various nonsymmetric ureas from protected amines. A variety of protected aromatic and aliphatic carbamates reacted readily with various amines in the presence of lanthanum triflate to generate the desired ureas in high yields. This result demonstrated that this novel lanthanum triflate catalyzed preparation of ureas from Cbz, Alloc, and Troc carbamates can be employed for the formation of various urea structures.
- Bui, Tien Tan,Kim, Hee-Kwon
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supporting information
p. 997 - 1002
(2020/06/17)
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- Visible-light-promoted oxidative desulphurisation: A strategy for the preparation of unsymmetrical ureas from isothiocyanates and amines using molecular oxygen
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A green and efficient visible-light promoted oxidative desulphurisation protocol has been proposed for the construction of unsymmetrical ureas under mild conditions with broad substrate scope and good functional group tolerance. Most appealingly, the reaction can proceed smoothly without adding any strong oxidants. Control experiments and computational studies support a mechanism involving water-assisted in situ generation of thioureas and photocatalytic oxidative desulphurisation. The present method provides a promising synthesis strategy for the formation of diverse and useful unsymmetrical urea derivatives in the fields of pharmaceutical and synthetic chemistry.
- Deng, Weiseng,Gan, Ziyu,Jiang, Yuan-Ye,Li, Guoqing,Yan, Qiuli,Yang, Daoshan
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supporting information
p. 2956 - 2962
(2020/06/17)
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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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- 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 ureas in the bio-alternative solvent Cyrene
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Cyrene as a bio-alternative solvent: a highly efficient, waste minimizing protocol for the synthesis of ureas from isocyanates and secondary amines in the bio-available solvent Cyrene is reported. This method eliminated the use of toxic solvents, such as
- Mistry, Liam,Mapesa, Kopano,Bousfield, Thomas W.,Camp, Jason E.
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supporting information
p. 2123 - 2128
(2017/07/24)
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- Accelerating effects of N-aryl-N′,N′-dialkyl ureas on epoxy-dicyandiamide curing system
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This report focuses on epoxy-dicyandiamide (DICY) curing system accelerated by N-aryl-N′,N′-dialkyl urea, aiming at clarifying the accelerating mechanism and the relationship between accelerating effect and molecular structure of the accelerators. Nine N-aryl-N′,N′-dialkyl ureas were synthesized and investigated with measurements of differential scanning calorimetry, thermo gravimetric/differential thermal analysis and NMR spectroscopy. The results revealed that the ureas released the corresponding secondary amines by the thermal dissociation in the presence of epoxide, which led to the formation of tertiary amines that catalyze the addition reaction of DICY to epoxide. Moreover, a tendency that the ureas able to release more compact amines exhibited higher acceleration effects was discovered.
- Liu, Xiang Dong,Kimura, Mika,Sudo, Atsushi,Endo, Takeshi
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experimental part
p. 5298 - 5305
(2011/06/21)
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- Synthesis of unsymmetrical ureas by sulfur-assisted carbonylation with carbon monoxide and oxidation with molecular oxygen under mild conditions
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With ambient pressure of carbon monoxide and oxygen at room temperature, N,N-dialkyl-N′-arylureas were selectively accessible from secondary amines, aromatic amines, and sulfur in good to excellent yields. For example, N-butyl-N-methyl-N′-(3,4-dichlorophenyl)urea, which is used as a herbicide (neburon), was afforded successfully from butylmethylamine (2 equiv), 3,4-dichloroaniline (1 equiv) and sulfur (1 equiv) in 79% (21.8 g) yield using carbon monoxide (0.1 MPa) and oxygen (0.1 MPa) at 20°C in DMF. Georg Thieme Verlag Stuttgart.
- Mizuno, Takumi,Nakai, Takeo,Mihara, Masatoshi
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experimental part
p. 2492 - 2496
(2009/12/08)
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- Organometallic chemistry and catalysis on gold metal surfaces
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As in transition metal complexes, C{triple bond, long}N-R ligands adsorbed on powdered gold undergo attack by amines to give putative diaminocarbene groups on the gold surface. This reaction forms the basis for the discovery of a gold metal-catalyzed reaction of C{triple bond, long}N-R, primary amines (R′NH2) and O2 to give carbodiimides (R′-N{double bond, long}C{double bond, long}N-R). An analogous reaction of C{triple bond, long}O, RNH2, and O2 gives isocyanates (R-N{double bond, long}C{double bond, long}O), which react with additional amine to give urea (RNH)2C{double bond, long}O products. The gold-catalyzed reaction of C{triple bond, long}N-R with secondary amines (HNR′2) and O2 gives mixed ureas RNH(C{double bond, long}O)NR′2. In another type of gold-catalyzed reaction, secondary amines HN(CH2R)2 react with O2 to undergo dehydrogenation to the imine product, RCH{double bond, long}N(CH2R). Of special interest is the high catalytic activity of gold powder, which is otherwise well-known for its poor catalytic properties.
- Angelici, Robert J.
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p. 847 - 856
(2008/03/30)
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- Thiol on silica as a 'catch and release' support for isocyanates to afford ureas
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Silica-bound thiocarbamates were prepared by Curtius rearrangement of carboxylic acids in the presence of thiol on silica gel. The solid supported thiocarbamates were found to be stable isocyanate equivalents, which upon treatment with amines efficiently afforded di- and tri-substituted ureas. The urea products released from the catch and release support were, in the majority of cases, greater than 95% pure and required no further work up.
- Bolshan, Yuri,Tomaszewski, Miroslaw J.,Santhakumar, Vijayaratnam
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p. 4925 - 4927
(2008/02/08)
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- Non-nanogold catalysis of carbon monoxide oxidative amination
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Bulk metallic gold particles (~1000 nm) catalyze the reaction of CO, O2, and primary amines (R-NH2) to give ureas (RNH)2C=O. Isocyanates (R-N=C=O) are identified as intermediates in the reactions and are shown to react with primary and secondary amines to give ureas under the conditions of the gold-catalyzed reactions. Although many recent studies indicate that nanosized particles of gold are required for the catalytic oxidation of CO, the results presented in this paper show that bulk gold is capable of catalyzing the oxidative amination of CO under mild conditions (45 °C, 1 atm CO and O2). Copyright
- Zhu, Bolin,Angelici, Robert J.
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p. 14460 - 14461
(2008/02/02)
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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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- Selenium-catalyzed reductive carbonylation of nitrobenzene with amines as coreagents to give unsymmetric phenylureas
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The reductive carbonylation of nitrobenzene catalyzed by selenium to yield unsymmetric phenylureas has been studied. When secondary amines were used as coreagents, a single product, PhNHCONR2, was formed; when primary amines were chosen as coreagents, mixed products, including RNHCONHR, RNHCONHPh and PhNHCONHPh, were obtained.
- Yang, Ying,Lu, Shiwei
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p. 4845 - 4846
(2007/10/03)
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- NEW ACYCLIC AND FUSED TRICYCLIC PHOSPHORUS COMPOUNDS AFFORDED BY NOVEL CONDENSATION
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The condensation of 1-(2-benzothiazolyl)-4-phenylsemicarbazide with (R2N)2PX (X = R2N, RO, Ph) proceeds with cleavage of the N-C(O) bond and formation of the title compounds which were also synthesized via similar treatment of 2-hydrazinobenzothiazole in good yields.Reactivities of (R2N)2PX, spectroscopic properties of the products and preliminary mechanism of these reactions were discussed.
- Zhang, Jing-Lin,Ma, Xiao-Bo
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p. 291 - 298
(2007/10/02)
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- NEW DERIVATIVES OF 4,5-BENZO-1,3,2-OXAZA (OR DIAZA)-PHOSPHOLANE FROM CONVENIENT CONDENSATION OF SUBSTITUTED UREA WITH TRIS(DIALKYLAMINO)PHOSPHINE
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The condensation of N-phenyl-N'-(2-hydroxylphenyl)urea or N-phenyl-N'-(2-aminophenyl)urea with tris(dialkylamino)phosphine afforded derivatives of 4,5-benzo-1,3,2-oxaza (or diaza)-phospholane which formed intramolecular hydrogen bond.The cleavage of the amide bond to give N,N-dialkyl-N'-phenylurea together with polymers of 1,3,2-benzodiazaphosphole was observed in the latter reaction.
- Ma, Xiao-bo,Zhang, Jing-lin
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p. 227 - 231
(2007/10/02)
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