(DPPA). The reactionprocedure is quite simple, occurring by refluxing an equimolecular mixture of a carboxylic acid, DPPA, and triethylamine in the presence of a hydroxyl component. Aromatic, aliphatic, and heterocyclic carboxylic acids underwent rearrangements in satisfactory yields. As this modified Curtins reaction is much simpler and less laborious than the classical Curtius reaction and proceeds
Iron-catalyzed urea synthesis: dehydrogenative coupling of methanol and amines
作者:Elizabeth M. Lane、Nilay Hazari、Wesley H. Bernskoetter
DOI:10.1039/c8sc00775f
日期:——
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 mechanisticinsights enabled the development of an iron-catalyzed method for the synthesis of unsymmetric
取代脲有许多应用,但它们的合成通常需要使用剧毒的起始材料。在此,我们描述了第一种通过甲醇与伯胺脱氢偶联选择性合成对称脲的贱金属催化剂。使用钳形负载铁催化剂,生成了一系列尿素,分离产率高达 80%(相当于催化转化率高达 160),且 H 2为唯一副产物。机理研究表明,从甲醇脱氢开始逐步生成甲醛,甲醛被胺捕获,生成甲酰胺。然后甲酰胺脱氢产生暂时的异氰酸酯,其与另一当量的胺反应形成脲。这些机理见解使得铁催化方法得以开发,用于从酰胺和胺合成不对称脲。
Practical Synthesis of Urea Derivatives from Primary Amines, Carbon Monoxide, Sulfur, and Oxygen under Mild Conditions
facile synthetic method for ureaderivatives was developed under mild conditions, and contrasts with conventional preparation methods that need highly toxic reagents (phosgene) or severe reaction conditions. In our reaction system, N,N-dimethylformamide or dimethyl sulfoxide as solvent strongly accelerated the carbonylation of primary amines with sulfur under carbonmonoxide (1 atm) at 20 °C to give the
在温和条件下开发了一种新的、简便的尿素衍生物合成方法,与需要剧毒试剂(光气)或苛刻反应条件的常规制备方法形成对比。在我们的反应体系中,N,N-二甲基甲酰胺或二甲基亚砜作为溶剂,在一氧化碳(1 atm)和 20 °C 下强烈加速伯胺与硫的羰基化反应,生成相应的硫代氨基甲酸盐。这些盐在类似温和的条件下很容易被分子氧氧化,以良好至极好的产率提供脲衍生物。这种尿素合成也可以应用于在 N,N-二甲基甲酰胺中使用 1,8-二氮杂双环[5.4.0]undec-7-ene 合成芳族脲的新方法。
Ruthenium-Catalyzed Urea Synthesis by N–H Activation of Amines
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
Co(acac)3/BMMImCl as a base-free catalyst system for clean syntheses of N,N′-disubstituted ureas from amines and CO2
作者:Jian Li、XiaoGuang Guo、LiGuo Wang、XiangYuan Ma、QingHua Zhang、Feng Shi、YouQuan Deng
DOI:10.1007/s11426-010-4026-8
日期:2010.7
A base-free catalyst system Co(acac)3/BMMImCl was developed for the carbonylation of amines with CO2. 45%\2-81% isolated yields for N,N-dialkylureas and 6%\2-23% isolated yields for N,N-diarylureas were obtained. The catalyst system was recovered and reused without significant loss in activity. In this catalyst system, the base catalyst and chemical dehydrant were efficiently avoided. Different reaction conditions were also discussed and a postulated mechanism was proposed.