1798-20-5Relevant articles and documents
Organic ligand and solvent free oxidative carbonylation of amine over Pd/TiO2 with unprecedented activity
Liu, Shujuan,Dai, Xingchao,Wang, Hongli,Shi, Feng
supporting information, p. 4040 - 4045 (2019/08/07)
A highly active Pd/TiO2 catalyst system was prepared and applied in the oxidative carbonylation of amines to ureas with ultra-low Pd content under organic ligand and solvent free conditions. The catalytic turnover frequencies (TOFs, moles of amines converted per mole of Pd per h) were 126000 and 250000 h-1 for the production of diphenylurea and dibenzylurea, respectively. An expanded substrate scope including the electron-rich and electron-deficient anilines, primary aliphatic amines, secondary amines was also established. This work offers a straightforward, step economic, and green methodology for the efficient synthesis of valuable ureas.
Iron-catalyzed urea synthesis: Dehydrogenative coupling of methanol and amines
Lane, Elizabeth M.,Hazari, Nilay,Bernskoetter, Wesley H.
, p. 4003 - 4008 (2018/05/04)
Substituted ureas have numerous applications but their synthesis typically requires the use of highly toxic starting materials. Herein we describe the first base-metal catalyst for the selective synthesis of symmetric ureas via the dehydrogenative coupling of methanol with primary amines. Using a pincer supported iron catalyst, a range of ureas was generated with isolated yields of up to 80% (corresponding to a catalytic turnover of up to 160) and with H2 as the sole byproduct. Mechanistic studies indicate a stepwise pathway beginning with methanol dehydrogenation to give formaldehyde, which is trapped by amine to afford a formamide. The formamide is then dehydrogenated to produce a transient isocyanate, which reacts with another equivalent of amine to form a urea. These mechanistic insights enabled the development of an iron-catalyzed method for the synthesis of unsymmetric ureas from amides and amines.
Ruthenium-Catalyzed Urea Synthesis by N-H Activation of Amines
Krishnakumar, Varadhan,Chatterjee, Basujit,Gunanathan, Chidambaram
supporting information, p. 7278 - 7284 (2017/06/23)
Activation of the N-H bond of amines by a ruthenium pincer complex operating via amine-amide metal-ligand cooperation is demonstrated. Catalytic formyl C-H activation of N,N-dimethylformamide (DMF) is observed in situ, which resulted in the formation of CO and dimethylamine. The scope of this new mode of bond activation is extended to the synthesis of urea derivatives from amines using DMF as a carbon monoxide (CO) surrogate. This catalytic protocol allows the synthesis of simple and functionalized urea derivatives with liberation of hydrogen, devoid of any stoichiometric activating reagents, and avoids the direct use of fatal CO. The catalytic carbonylation occurred at low temperature to provide the formamide; a formamide intermediate was isolated. The consecutive addition of different amines provided unsymmetrical urea compounds. The reactions are proposed to proceed via N-H activation of amines followed by CO insertion from DMF and with liberation of dihydrogen.
