1801-72-5Relevant academic research and scientific papers
Cyclodimerization of isocyanates promoted by one large vertex metallaborane
Ma, Pei,Spencer, James T.
, p. 148 - 152 (2018/06/26)
The 10-vertex Manganese-decaborane [nido-6-Mn(CO)3B9H13][NMe4] was found to act as an efficient catalyst for isocyanate cyclodimerization under photo-irradiation conditions. The reaction yields were comparable with other metal catalyst reported in literature. One of the products was characterized by X-ray crystallographic study and reaction mechanism was also proposed. The results are very encouraging as they represent first examples of a large metallaborane compound to catalyze the cyclodimerization of isocyanates.
CeO2-catalyzed direct synthesis of dialkylureas from CO2 and amines
Tamura, Masazumi,Ito, Kazuki,Nakagawa, Yoshinao,Tomishige, Keiichi
, p. 75 - 85 (2016/11/11)
CeO2 showed higher activity for the direct synthesis of 1,3-dibutylurea (DBU) from CO2 and n-butylamine than the metal oxides tested. The solvent largely influenced the reaction over CeO2, and N-methylpyrrolidone (NMP) was preferable among various solvents tested from the viewpoints of activity and selectivity. The catalyst system composed of CeO2 catalyst and NMP solvent (CeO2 in NMP) was applicable to the reactions of various amines such as linear primary alkylamines or branched primary alkylamines, although tert-butylamine afforded low conversion. In contrast, secondary amines and aniline provided no yield of the ureas. The combination of 2-cyanopyridine with CeO2 in NMP (CeO2 in NMP with 2-cyanopyridine) promoted the transformation of the unreactive amines, showing that tert-butylamine and aniline were converted to the corresponding ureas in 82% and 80% yields, respectively. These yields are much higher than those reported in the previous literatures, indicating that CeO2 in NMP with 2-cyanopyridine drastically promoted transformation of amines with low reactivity.
Cyclodimerization and cyclotrimerization of isocyanates promoted by one praseodymium benzenethiolate complex [Pr(SPh)3(THF)3]
Wang, He-Ming,Li, Hong-Xi,Yu, Xiang-Yang,Ren, Zhi-Gang,Lang, Jian-Ping
experimental part, p. 1530 - 1535 (2011/04/15)
The cyclotrimerization of aryl isocyanates and the cyclodimerization of alkyl isocyanates initiated by one praseodymium benzenethiolate complex [Pr(SPh)3(THF)3] were investigated. Comparative runs with [Pr(SPh)3(THF)3] and its precursor Pr[(Me 3Si)2N]3 showed that the former has the advantages of a higher selectivity toward isocyanates, easy preparation, low catalyst loading, high conversion as well as mild reaction conditions.
Lanthanide(III) 4,6-dimethylpyrimidine-2-thionate complexes as efficient catalysts for isocyanate cyclodimerization
Li, Hong-Xi,Cheng, Mei-Ling,Wang, He-Ming,Yang, Xiao-Juan,Ren, Zhi-Gang,Lang, Jian-Ping
experimental part, p. 208 - 214 (2011/03/17)
Protonolysis reactions of [(Me3Si)2N] 3Ln(μ-Cl)Li(THF)3 (Ln = Pr, Nd, Sm, Eu) with 3 equiv of 4,6-dimethylpyrimidine-2-thiol (dmpymtH) gave rise to the four Ln(III) pyrimidine-2-thionate complexes Li[Ln(dmpymt)4] (Ln = Pr (1), Nd (2), Sm (3), Eu (4)). Compounds 1-4 were characterized by elemental analysis, IR and 1H NMR spectroscopy, and single-crystal X-ray diffraction. X-ray diffraction analysis shows that the structures of 1-4 are similar and each eight-coordinate Ln(III) ion is chelated by four dmpymt ligands. Complexes 1-4 display excellent catalytic performance in the cyclodimerization of isocyanates to produce substituted ureas via elimination of CO, which represents the first example of lanthanide thiolates exhibiting a high catalytic activity and a high selectivity in the cyclodimerization of isocyanates. The effects of the solvents, temperatures, catalyst loadings, and rare-earth metals on the catalytic activities of the complexes were examined.
Organocatalyzed synthesis of ureas from amines and ethylene carbonate
Saliu, Francesco,Rindone, Bruno
experimental part, p. 6301 - 6304 (2011/01/04)
A new solventless method for the synthesis of symmetrical and unsymmetrical ureas, starting from ethylene carbonate and amines, is reported. 1,5,7-Triazabicyclo[4.4.0]dec-5-ene(TBD) and thioureas have been found to be efficient organocatalysts for this reaction.
Synthesis of urea derivatives from amines and CO2 in the absence of catalyst and solvent
Wu, Chaoyong,Cheng, Haiyang,Liu, Ruixia,Wang, Qiang,Hao, Yufen,Yu, Yancun,Zhao, Fengyu
experimental part, p. 1811 - 1816 (2011/02/22)
Urea derivatives are obtained in mild to good yield from the reactions of primary aliphatic amines with CO2 in the absence of any catalysts, organic solvents or other additives. To optimize reaction conditions, experimental variables including temperature, pressure, the concentration of amine, reaction time etc. were studied. Satisfactory yields were obtained at the optimized conditions that are comparable to the presence of catalyst and solvent. The preliminary investigation of the reaction mechanism showed that alkyl ammonium alkyl carbamate was quickly formed as the intermediate, and then the final product was formed by the intramolecular dehydration.
Cobalt/rhodium heterobimetallic nanoparticle-catalyzed oxidative carbonylation of amines in the presence of carbon monoxide and molecular oxygen to ureas
Park, Ji Hoon,Yoon, Jae Chun,Chung, Young Keun
supporting information; experimental part, p. 1233 - 1237 (2009/12/07)
An environmentally friendly oxidative carbonylation of aliphatic and aromatic primary amines to ureas has been successfully achieved in the presence of a catalytic amount of cobalt/rhodium heterobimetallic nanoparticles without any promoters. The catalyst system could be reused with only a slight loss of catalytic activity.
Ruthenium-catalyzed allenyl carbamate formation from propargyl alcohols and isocyanates
Haak, Edgar
supporting information; experimental part, p. 788 - 792 (2009/04/11)
Ruthenium complexes of redox-coupled cyclopentadienone ligands catalyze the formation of allenyl carbamates from propargyl alcohols and isocyanates. This efficient and atom-economical process represents the first catalytic access to allenyl carbamates, co
Preparation of mono-, di-, and trisubstituted ureas by carbonylation of aliphatic amines with S,S-dimethyl dithiocarbonate
Artuso, Emma,Degani, Iacopo,Fochi, Rita,Magistris, Claudio
, p. 3497 - 3506 (2008/09/19)
General procedures are reported to prepare N-alkylureas, N,N′-dialkylureas (both symmetrical and unsymmetrical), and N,N,N′-trialkylureas by carbonylation of aliphatic amines, employing S,S-dimethyl dithiocarbonate (DMDTC) as a phosgene substitute. All reactions were carried out in water. Symmetrical disubstituted ureas were prepared directly working at 60°C with a molar ratio of DMDTC:amine = 1:2, preferably under nitrogen. Unsymmetrical ureas were prepared in two steps via S-methyl N-alkyl-thiocarbamate intermediates, which are formed selectively in the first step at room temperature. These intermediates react in the second step with ammonia or various aliphatic amines, both primary and secondary, at temperatures varying between 50 and 70°C. All the target ureas were obtained in high yields (28 examples, average yield 94%) and with very high purity (generally >99.2%). Also to be noted is the recovery of a co-product of industrial interest, methanethiol, in an amount of two moles for each mole of DMDTC, with complete exploitation of the reagent. Georg Thieme Verlag Stuttgart.
Organosilicon synthesis of isocyanates: II. Synthesis of aliphatic, carbocyclic, and fatty-aromatic isocyanates
Lebedev,Lebedeva,Sheludyakov,Ovcharuk,Kovaleva,Ustinova
, p. 469 - 477 (2008/02/07)
Silylation of a series of aliphatic, carbocyclic, and fatty-aromatic amines gave the corresponding silyl derivatives whose yield depended on the electronic and steric structure of the substrate and the nature of the silylating agent. The yield of isocyanates obtained by phosgenation of the silyl derivatives under mild conditions decreased in going from aliphatic amines to benzylamines and rose as the length of the alkyl chain in fatty-aromatic amines extended. The most convenient procedure for the synthesis of low-boiling alkyl isocyanates was found to be based on the transformation of amines or ammonium salts into silyl or silyl silyl-carabamates, followed by pyrolysis of the latter in the presence of trichloro(phenyl)silane. Pleiades Publishing, Inc., 2006.
