First practical synthesis of formamidine ureas and derivatives

Isonitriles and ureas undergo a condensation reaction in the presence of acid chlorides to give formamidine ureas, for which no general synthetic routes currently exist. A mechanism is proposed in which the key intermediate is an electrophilic adduct of isonitrile and acid chloride. The process is tolerant of moderate variability in the nature of the components, and access to formamidine ureas of varying substitution patterns is further enhanced by a facile exchange reaction with amines. [reaction: see text]     

Super fast cobalt carbonyl-mediated synthesis of ureas

Fast cobalt carbonyl-mediated generation of ureas from primary amines was performed using high-density microwave irradiation. This enhanced method permitted the preparation of symmetrical ureas in good yields and unsymmetrical ureas in moderate yields. The reaction times varied between 10 s and 40 min. The proposed mechanism for the reaction includes in situ generation of an intermediate isocyanate that subsequently traps the free amine, producing the urea product.     

非对称取代脲的合成与应用

总结了合成非对称取代脲的几种方法，分析了各种方法的利弊，介绍了非对称 取代脲的主要应用，指出直接利用一氧化碳进行硒催化的胺与硝基化合物的氧化还 原羰基化反应来合成非对称取代脲的方法是比较有发展前景的方法，并对硒催化的 氧化还原羰基化反应作了较为详细的介绍。     

Parallel synthesis of tri- and tetrasubstituted ureas from carbamoyl imidazolium salts

A method for producing tri- and tetrasubstituted ureas from carbamoyl imidazolium salts is presented. Carbamoyl imidazolium salts are prepared from the reaction of N,N carbonyldiimidazole (CDI) with secondary amines, followed by alkylation with iodomethane. These stable salts can be stored for extended periods and are effective electrophilic carbamoylation reagents. Primary and secondary amines add to carbamoyl imidazolium salts at room temperature to give tri- and tetrasubstituted ureas in excellent yields. This reaction was used to synthesize ureas using both liquid-liquid extraction and solid-phase extraction (cation exchange) purification techniques. Liquid-liquid extraction affords the product ureas more cleanly than cationic exchange. A series of urea compounds were synthesized using parallel synthesis techniques in high yields and with suitable purity for routine in vitro biological tests. These studies validate the utility of carbamoyl imidazolium salts as useful building blocks for combinatorial library synthesis.     

Practical synthesis of unsymmetrical ureas from isopropenyl carbamates

A very convenient method for the synthesis of unsymmetrical ureas is described, based on isopropenyl carbamates. The synthetic efficiency of traditional methods for urea formation, such as use of phosgene or alkyl and aryl carbamates, is limited by the formation of symmetrical urea side products or reaction reversibility. Isopropenyl carbamates react with amines cleanly and irreversibly and give unsymmetrical ureas in high yield and purity. This method is ideal for the rapid synthesis of compound libraries.     

The direct conversion of carbamates to ureas using aluminum amides

The conversion of carbamates into ureas using aluminum amide complexes is reported. This reaction is a convenient method to prepare bi-, tri- and tetra-substituted ureas from carbamate-protected primary or secondary amines by reaction with primary or secondary amines in the presence of stoichometric quantities of trimethylaluminum. A reactivity trend of the various carbamates was observed and methyl and benzyl carbamates were reacted selectively in the presence of t-butyl carbamates.     

Expanded chemistry of formamidine ureas

[reaction: see text] Formamidine ureas display a rich manifold of reactivity. Thiols induce substitution at the carbonyl carbon to give thiolcarbamates; base-mediated alkylation and acylation occurs at the terminal urea nitrogen, and a new fragmentation/acylation pathway has been uncovered with isocyanates.     

A simple and efficient synthesis of new cyclic ureas

A facile access to a wide range of original saturated N-heterocyclic ureas is described using, as a key step, a Michael-type reaction involving isocyanates or amines on a piperidine framework possessing an α,β-unsaturated ester functionality.     

An efficient direct amination of cyclic amides and cyclic ureas

[reaction: see text] An efficient one-step amination of cyclic amides and ureas has been developed. Treatment of cyclic amides and cyclic ureas with BOP in the presence of DBU in various solvents led to the formation of cyclic amidines and cyclic guanidines in good to excellent yields. Concise syntheses of biologically intriguing kinetin and potent kinase inhibitor olomoucin were thus achieved in just one and two steps, respectively.     

Selective catalytic oxidative carbonylation of amino alcohols to ureas

[reaction: see text] Amino alcohols undergo W(CO)(6)-catalyzed oxidative carbonylation to the corresponding hydroxyalkylureas without protection of the hydroxyl group. Selected examples of 1,2-, 1,3-, 1,4-, and 1,5-amino alcohols were converted to the ureas in good to excellent yields, with only small amounts of the cyclic carbamates being formed. In contrast, the phosgene derivatives CDI and DMDTC undergo stoichiometric reactions with the amino alcohol substrates to afford ureas and cyclic carbamates with variable selectivity.     

A general method for the solid-phase synthesis of unsymmetrical tri- and tetrasubstituted ureas

A general method for the preparation of unsymmetrical di, tri-, and tetrasubstituted ureas on polymer supports is presented. Polymer-bound primary and secondary amines react with imidazolium salts (urea donors), which are generated from the reaction of N,N'-carbonyldiimidazole (CDI) with primary and secondary amines followed by alkylation with MeI to give tri- and tetrasubstituted ureas in excellent yields (76-98%) and purities (80-99%).     

5 + 2] Cycloaddition reaction of 2-vinylaziridines and sulfonyl isocyanates. Synthesis of seven-membered cyclic ureas

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.     

相转移催化合成偶氮脲

取代氨基脲的两相转移催化脱氢合成偶氮脲是一种新反应, 本文报道了用2, 4, 6-三叔丁基苯酚两相转移催化取代氨基脲脱氢形成偶氮化合物, 在温和的条件下合成了10个新偶氮脲, 均获得较好的产率(88-99%), 并对其反应机理作了合理的解释。     

Microwave-assisted preparation of cyclic ureas from diamines in the presence of ZnO

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.     

Organocatalyzed synthesis of ureas from amines and ethylene carbonate

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 some pyridyl substituted ureas and thioureas

Thirty five pyridyl-substituted ureas and thioureas were synthesized in order to study the relationship between chemical structure and biological activity. These compounds were obtained by the reaction of pyridylamines with isocyanates and isothiocyanates, as well as by the desulfurization of the corresponding thioureas. When tested, all these compounds exhibited weak physiological activity.     

A facile synthesis of unsymmetrical ureas

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.     

Stereospecific synthesis of the alpha- and beta-D-glucopyranosyl ureas

A new, one-pot, two-stage procedure for the preparation of the alpha- and beta-D-glucopyranosyl ureas has been developed. Oxidation of glucopyranosyl isocyanides provides glucopyranosyl isocyanates, which can be trapped in situ with amines to afford good yields of glucopyranosyl ureas. Application of this method establishes the successful synthesis of the hitherto unknown N,N'-di-alpha,alpha- and alpha,beta-D-glucopyranosyl ureas.     

Metal-free synthesis of pyridin-2-yl ureas from 2-aminopyridinium salts

An unprecedented base promoted domino approach has been developed for the synthesis of pyridin-2-yl urea derivatives via the reaction of 2-aminopyridinium salts and arylamines. The developed strategy tolerated a wide range of functional groups and afforded pyridin-2-yl ureas in moderate to good yields. The reaction was postulated to involve tandem cyclization, intermolecular nucleophilic addition, ring opening, and demethylation.     

含有偶氮染料侧基的聚氨酯（脲）的研究

用扩链法合成了一系列含有偶氮染料的侧基聚氨酯和聚脲。ＴＦ－ＩＲ、ＤＳＣ、ＤＭＡ的研究表明，聚合物有良好的力学性能，样品中软硬段的含量决定材料的物理性能。通过ＵＶ的测定，计算出样品均有较高的三阶非线性光学（ＮＬＯ）系数。