15942-15-1Relevant articles and documents
P(III)-Assisted Electrochemical Access to Ureas via in situ Generation of Isocyanates from Hydroxamic Acids
Meng, Haiwen,Sun, Kunhui,Xu, Zhimin,Tian, Lifang,Wang, Yahui
supporting information, p. 1768 - 1772 (2021/03/26)
An external oxidant-free protocol for the generation of isocyanates from hydroxamic acids assisted by trivalent phosphine under mild electrochemical conditions was reported. The process started with the anodic oxidation of hydroxamic acids, followed by reacting with phosphine to form corresponding alkoxyphosphoniums and subsequent rearrangement with the release of tri-substituted phosphine oxide as the driving force to give isocyanates, which were trapped by N-based nucleophiles to produce various ureas. This method provides a broadly applicable procedure to access isocyanate intermediates under mild electrochemical conditions.
Lanthanum(III) Trifluoromethanesulfonate Catalyzed Direct Synthesis of Ureas from N-Benzyloxycarbonyl-, N -Allyloxycarbonyl-, and N -2,2,2-Trichloroethoxycarbonyl-Protected Amines
Bui, Tien Tan,Kim, Hee-Kwon
supporting information, p. 997 - 1002 (2020/06/17)
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.
Chemoselective isocyanide insertion into the N-H bond using iodine-DMSO: Metal-free access to substituted ureas
Bora, Porag,Bez, Ghanashyam
supporting information, p. 8363 - 8366 (2018/08/03)
Insertion of isocyanides into the N-H bond gives access to many medicinally important and structurally diverse complex nitrogen-containing heterocycles. Although the transition metal catalyzed isocyanide insertion into the N-H bond is very common, polymerization of isocyanides in the presence of a transition metal and their strong coordination with metals are the common drawbacks. On the other hand, the inertness of most of the isocyanides towards amines in the absence of a metal catalyst has stymied the growth of the metal-free approach for isocyanide insertion into amines. As a result, only a handful of metal catalysed methods with limited substrate scopes have been reported for the synthesis of ureas via isocyanide insertion into amines and no metal-free version has been reported yet. Interestingly, chemoselective isocyanide insertion into amines has not been reported in the literature. We employed the I2-DMSO reagent system for the chemoselective synthesis of ureas, where isocyanides react with aliphatic amines only, while aromatic amines need a nucleophilic activator (DABCO) to facilitate the formation of ureas. This method gave direct and chemoselective access to ureas by evading the commonly used yet toxic isocyanates.
Stoichiometric Reactions of CO2 and Indium-Silylamides and Catalytic Synthesis of Ureas
Xu, Maotong,Jupp, Andrew R.,Stephan, Douglas W.
supporting information, p. 14277 - 14281 (2017/10/31)
The indium compounds In(N(SiMe3)2)2Cl?THF (2) and In(N(SiMe3)2)Cl2?(THF)n (3) were shown to react with CO2 to give [(Me3Si)2N)InX(μ-OSiMe3)]2 (X=N(SiMe3)2 4, Cl 5). 0.05–2.0 mol % of the species 3 acts as a pre-catalyst for the conversion of aryl and alkyl silylamines under CO2 (2–3 atm) to give the corresponding ureas in 70–99 % yields. A proposed mechanism is supported by experimental and computational data.
A high-yielding, expeditious, and multicomponent synthesis of urea and carbamate derivatives by using triphenylphosphine/trichloroisocyanuric acid system
Ghodsinia, Sara S.E.,Akhlaghinia, Batool
, p. 104 - 110 (2016/01/25)
An efficient method for the synthesis of urea and carbamate derivatives from amines and alcohols is described by using triphenylphosphine (PPh3)/trichloroisocyanuric acid system. The protocol allows for the preparation of symmetrical, unsymmetrical di, tri-, and tetra-substituted ureas and carbamates and is tolerant of a wide range of functional groups. To optimize the reaction conditions, experimental variables including temperature, the concentration of amine and alcohol, solvent, and reaction time were studied. Satisfactory yields were obtained at the optimized conditions. The present methodology is experimentally simple, mild, and represents a valuable alternative to the existing methods.
Facile one-pot synthesis of unsymmetrical ureas, carbamates, and thiocarbamates from Cbz-protected amines
Kim, Hee-Kwon,Lee, Anna
supporting information, p. 7345 - 7353 (2016/08/05)
A novel one-pot synthesis of unsymmetrical ureas, carbamates and thiocarbamates from Cbz-protected amines has been developed. In the presence of 2-chloropyridine and trifluoromethanesulfonyl anhydride, isocyanates are generated in situ, which facilitate rapid reaction with amines, alcohols, and thiols to afford the corresponding ureas, carbamates and thiocarbamates in high yields.
An easy access to unsymmetrical ureas: A photocatalytic approach to the Lossen rearrangement
Yadav, Arvind K.,Srivastava, Vishnu P.,Yadav, Lal Dhar S.
, p. 24498 - 24503 (2014/07/07)
An efficient and operationally simple method for the synthesis of unsymmetrical ureas from various hydroxamic acids and amines has been developed. Plausibly, the protocol involves visible-light-initiated in situ formation of Vilsmeier-Haack reagent and COBr2 with CBr4 and a catalytic amount of DMF in the presence of Ru(bpy)3Cl2 as a photocatalyst to bring about the Lossen rearrangement at room temperature. the Partner Organisations 2014.
Iron(III) catalysed synthesis of unsymmetrical di and trisubstituted ureas - A variation of classical Ritter reaction
Basavaprabhu, Hosamani,Sureshbabu, Vommina V.
, p. 2528 - 2533 (2012/04/23)
An application of the classical Ritter reaction for the synthesis of unsymmetrical di and trisubstituted ureas catalyzed by FeCl3 is described. The protocol is of significant interest in view of the easy availability of precursors, mild reaction conditions employed and interestingly its applicability for the alkylation of alcohols capable of forming stable carbocationic intermediates even to the sterically hindered moieties. The Royal Society of Chemistry 2012.
Synthesis of ureas from titanium imido complexes using CO2 as a C-1 reagent at ambient temperature and pressure
Anderson, James C.,Moreno, Rafael Bou
supporting information; experimental part, p. 1334 - 1338 (2012/04/10)
The coordinatively unsaturated 12-electron complex dichloro t-butylimido bispyridine titanium(iv) (2a) has been shown to react with CO2 to give N,N-bis-t-butyl urea. Two analogous sterically hindered coordinatively saturated 14-electron complexes dichloro t-butylimido trispyridine titanium(iv) (10a) and dichloro 2,6-(i-Pr)2phenylimido trispyridine titanium(iv) (10b) also gave their corresponding symmetrical ureas upon treatment with CO2. Further experiments support the intermediary of metallocycles formed from heterocumulene metathesis reactions. The unsymmetrical urea N-benzyl, N-t-butyl urea (11) was produced from treatment of 2,6-(i-Pr) 2phenylimido trispyridine titanium(iv) (10b) with CO2 and interception with BnNH2. Equimolar quantities of N,N- bistrimethylsilybenzylamine or N,N-bistrimethylsilyphenethylamine were shown to promote the reaction between t-butylimido bispyridine titanium(iv) (2a) and CO2 to give near quantitative yields of symmetrical urea. Other symmetrical ureas could be produced from TiCl4, amine and CO 2 in moderate to quantitative yields depending on the stoichiometry of amine present.
Palladium-catalyzed amidation of N-tosylhydrazones with isocyanides
Zhou, Fengtao,Ding, Ke,Cai, Qian
experimental part, p. 12268 - 12271 (2011/11/29)
Aminocarbonylation of N-tosylhydrazones: The direct formation of ketenimines from carbenes and isocyanides is limited to the reaction of Fischer carbene complexes or some specially stabilized carbenes with isocyanides. A Pd-catalyzed amidation of N-tosylhydrazones with isocyanides via a ketenimine intermediate in the presence of water is described. The method offers a general way to synthesize amides from carbonyl compounds through one-carbon extension (see scheme). Copyright
