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1.
Alkylation of O-silylated N-alkylmalonylhydroxamic acids provides a method for the synthesis of 2-substituted N-alkylmalonyl hydroxamic acids. The substituent at C-2 does not materially change the chemistry of the alpha-lactam intermediates produced from them. They can be converted to unsymmetric ureas and hydantoins in high yields. The addition of unsaturated substituents at C-2 is used to produce cyclic ureas containing medium rings via RCM reactions. 相似文献
2.
Catalytic aminolysis of oxalates by simple and substituted ureas has been shown to give carbamates, oxamates and derivatives of imidazolidine trione. Various substituted ureas and oxalates were screened to verify the applicability of the protocol. The role of dibutyltin oxide as catalyst, effect of solvent and reaction conditions on product distribution pattern has been discussed. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
3.
硒催化法合成2-吡啶脲的研究 总被引:4,自引:0,他引:4
采用硒催化的一氧化碳还原羰基化法,由硝基苯衍生物与2-氨基吡啶进行反应,得到的不是比例相当的三种脲类物质混合物,而主要得到非对称的吡啶脲.进一步发展了硒/一氧化碳催化体系对硝基化合物的还原羰基化法,可望用来合成一系列含取代基的苯基吡啶基脲类物质;该合成方法工艺简单,操作易行.对部分产物进行了红外光谱、核磁共振谱、高压液相色谱及元素分析等鉴定. 相似文献
4.
Andrey V. BogolubskySergey V. Ryabukhin Sergey E. PipkoOleg Lukin Alexander Shivanyuk Dmytro MykytenkoAndrey Tolmachev 《Tetrahedron》2011,67(20):3619-3623
A facile and versatile method for the synthesis of unsymmetrical ureas from readily available reagents is reported. In the first step trifluoroethylchloroformate is reacted with a stoichiometric amount of a primary amine to give an intermediate trifluoroethyl carbamate. The addition of a second amine (primary or secondary) to the trifluoroethyl carbamate furnishes corresponding unsymmetrical ureas in 75-85% yield. A simple workup procedure, the high yields obtained, and the purity of the isolated products are suitable for the parallel synthesis of combinatorial libraries of unsymmetrical ureas with high structural and functional diversity. 相似文献
5.
6.
The 13C-chemical shifts of methyl substituted ureas, thioureas and related compounds are reported and discussed. π-Electron densities, as obtained by simple HMO calculations, do not reproduce the 13C-chemical shift trend. A correlation has been found for the carbonyl and thiocarbonyl resonances which has been discussed as being mainly influenced by the mean excitation energy in the paramagnetic screening term. 相似文献
7.
Yong Jin Kim 《Tetrahedron letters》2004,45(39):7205-7208
A microwave-assisted facile method for the preparation of various ureas, cyclic ureas, and urethanes has been developed that affords nearly quantitative yield of products at 120 °C (150 W), 71 kPa within 10 min using ZnO as a catalyst. The enhanced selectivity in this reaction is attributed to the deployment of ZnO whose absence results in poor yield and the generation of byproducts. 相似文献
8.
《Tetrahedron》2019,75(44):130621
An efficient regioselective and operationally simple urea bromination method utilizing PIDA and potassium bromide is reported. This protocol proved to be effective on a broad range of substituted ureas in acetone at room temperature, forming the p-brominated compounds in 44–86% yields. 相似文献
9.
<正>A new practical method for the synthesis of unsymmetrical ureas was achieved by reaction of phenylurea with primary and secondary amines under neutral and mild condition in very good yields.The reaction took place in refluxing dioxane and does not require any catalyst or additives. 相似文献
10.
Stephen StokesNathaniel G. Martin 《Tetrahedron letters》2012,53(36):4802-4804
A novel, operationally simple, method for the preparation of acyl ureas is described. The procedure is high yielding and tolerant of a wide range of functional groups. 相似文献
11.
Derek Wodka 《Tetrahedron letters》2006,47(11):1825-1828
Carboxylic acids upon treatment with Burgess reagent are converted to novel mixed sulfocarboxy anhydrides. Subsequent treatment of such mixed anhydrides with amines at elevated temperatures yields acyl ureas and amides. The ratio of the two products appears to be temperature controlled. The method provides a simple and convenient route to diverse acyl ureas starting from carboxylic acids and amines. 相似文献
12.
N,N′‐Disubstituted ureas were efficiently synthesized by reactions of urea with a variety of amines in water under microwave irradiation using CeCl3 · 7H2O‐KI as catalyst. This protocol has advantages of not using toxic phosgene and hazardous organic solvents, high reaction rate, high yield, and a simple workup procedure. 相似文献
13.
Symmetrically N,N′-disubstituted ureas/thioureas were synthesized by heating amines or phenyl hydrazine and urea/thiourea on a preheated hot plate at 80–85°C under solvent-free conditions in the presence of a catalytic amount of ZnCl2 as a catalyst. The protocol has the advantages of not using toxic phosgene and other hazardous substrates or organic solvents. Increased reaction rate, good yield, and a simple workup procedure are involved. 相似文献
14.
Dr. Tongxiang Lu Prof. Steven E. Wheeler 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(45):15141-15147
The Diels–Alder cycloaddition of anthracene and nitrostyrene catalyzed by the squaramide‐derived aminocatalysts ( Sq ) recently reported by Jørgensen and co‐workers (Angew. Chem. 2012 , 124, 10 417; Angew. Chem. Int. Ed. 2012 , 51, 10 271) has been studied by using modern tools of computational quantum chemistry. This catalyst is compared with analogous urea‐, thiourea‐, and thiosquaramide‐derived aminocatalysts. Ultimately, a thiosquar‐amide‐derived catalyst is predicted to result in the lowest free‐energy barrier, while retaining the same high degree of enantioselectivity as Sq . This stems in part from the superior hydrogen‐bonding ability of thiosquaramides, compared to squaramides and (thio)ureas. We also examine the hydrogen‐bonding ability of (thio)ureas and (thio)‐squaramides in model complexes. In contrast to previous work, we show that aromaticity does not contribute significantly to the enhanced hydrogen‐bonding interactions of squaramides. Overall, thiosquaramide, which has not been explored in the context of either organocatalysis or molecular recognition, is predicted to lead to strong, co‐planar hydrogen bonds, and should serve as a potent hydrogen‐bonding element in a myriad of applications. 相似文献
15.
At this circumstance for the first time, a facile and convenient method for heteroaryl ureas has been developed via a two-step process involving in situ C–OH activation followed by palladium catalyzed C–N coupling of heteroarenols with ureas, which show excellent functional group tolerance and give out rapid coupling in good to excellent yield. 相似文献
16.
A simple and efficient method for the synthesis of 7,8‐diaminopelargonic acid, a key intermediate in the biotin biosynthesis pathway, is reported. The d‐desthiobiotin powder was dissolved in concentrated hydrochloric acid, and the solution was exposed to microwave radiation of 2.45 GHz for varying lengths of time ranging from 60 s to 2 min. The product thus obtained was characterized by spectroscopic techniques and confirmed through bioassay. Further, the protocol was extended to the synthesis of several diamines from their corresponding cyclic ureas. The results show that the method is generally applicable and not only accelerates the hydrolysis reaction but also offers excellent yields. 相似文献
17.
Kanno E Yamanoi K Koya S Azumaya I Masu H Yamasaki R Saito S 《The Journal of organic chemistry》2012,77(5):2142-2148
The [5 + 2] cycloaddition reaction of 2-vinylaziridines with sulfonyl isocyanates proceeded smoothly under mild conditions, and various cyclic ureas were isolated in high yields. The remarkable solvent effect on the reaction was observed, and the preferential formation of the seven-membered ring occurred when the reaction was carried out in CH(2)Cl(2). The scope and limitation were studied, and the mechanism of this reaction was discussed. This study provides a new and simple method for the synthesis of seven-membered cyclic ureas. 相似文献
18.
Abdigali A. Bakibaev Artur Uhov Victor S. Malkov Svetlana Yu. Panshina 《Journal of heterocyclic chemistry》2020,57(12):4262-4270
Most of the known methods for the synthesis of heterocyclic compounds have disadvantages, such as a long reaction time and aggressive conditions. We have developed a new, rather simple and efficient method for the synthesis of a number of glycoluryls and hydantoins in water using a etidronic acid (HEDP) as “Green catalyst.” So, for the first time, the condensation reaction of ureas with 1, 2-dicarbonyl compounds was carried out in the presence of HEDP. Also based on NMR studies, a chemism of these reactions, which is stepwise, is proposed. It has been established that the optimal conditions for the synthesis of glycoluryls and hydantoins using HEDP are: temperature 80°C-90°C, 40-20 minutes, and the ratio of urea and HEDP is 1:1. In all cases, the remaining aqueous filtrate containing HEDP after the reaction can be reused for other cycles synthesis of glycoluril and other compounds, because HEDP is not converted during the reaction. 相似文献
19.
A novel and environmentally benign synthetic method for ureas through hydrogen peroxide–promoted desulfurization of thioureas at room tepemperature via grinding is reported. As compared with the traditional method, this one is manipulatively simple and the oxidant is low cost, highly active, and environmentally friendly. 相似文献
20.
A simple one pot procedure for the synthesis of N,N'-unsymmetrical ureas using phenyl chloroformate in THF is described. 相似文献