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1.
One‐pot, three‐component condensation of 2‐naphthol, amides/ureas, and aldehydes takes place smoothly in the presence of cation‐exchange resins to afford the corresponding 1‐amidoalkyl‐2‐naphthols in good yield. Indion‐130 is found to be the best catalyst for the reaction and is recyclable. The method is simple, solvent free, and involves a short reaction time. 相似文献
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<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
4.
Synthesis of N−H Bearing Imidazolidinones and Dihydroimidazolones Using Aza‐Heck Cyclizations
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Feiyang Xu Dr. Scott A. Shuler Prof. Dr. Donald A. Watson 《Angewandte Chemie (International ed. in English)》2018,57(37):12081-12085
The synthesis of unsaturated, unprotected imidazolidinones via an aza‐Heck reaction is described. This palladium‐catalyzed process allows for the cyclization of N‐phenoxy ureas onto pendant alkenes. The reaction has broad functional group tolerance, can be applied to complex ring topologies, and can be used to directly prepare mono‐ and bis‐unprotected imidazolidinones. By addition of Bu4NI, dihydroimidazolones can be accessed from the same starting materials. Improved conditions for preparing unsaturated, unprotected lactams are also reported. 相似文献
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Consecutive Ring Expansion and Contraction for the Synthesis of 1‐Aryl Tetrahydroisoquinolines and Tetrahydrobenzazepines from Readily Available Heterocyclic Precursors
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Jessica E. Hill Dr. Johnathan V. Matlock Dr. Quentin Lefebvre Dr. Katie G. Cooper Prof. Jonathan Clayden 《Angewandte Chemie (International ed. in English)》2018,57(20):5788-5791
Tetrahydroisoquinolines and tetrahydrobenzazepines were prepared by acid‐promoted ring contraction of cyclic ureas, which were themselves formed by ring expansion of indolines and tetrahydroquinolines. The consequent overall one‐carbon insertion reaction gives these 6‐ and 7‐membered heterocyclic scaffolds in three steps from readily available precursors. Other ring sizes may be formed by an alternative elimination reaction of bicyclic structures. Scalability of the method was demonstrated by operating it in a flow system. 相似文献
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NIS/PhI(OAc)2‐Mediated Diamination/Oxidation of N‐Alkenyl Formamidines: Facile Synthesis of Fused Tricyclic Ureas
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Dr. Jun Zhang Weijie Wu Xuejun Zhang Gengtao Zhang Dr. Sheng Xu Prof. Dr. Min Shi 《化学:亚洲杂志》2015,10(3):544-547
Facile synthesis of bicyclic ureas by NIS/PhI(OAc)2‐mediated diamination/oxidation of N‐alkenyl formamidines is reported. Bulky aromatic groups such as 2,6‐diisopropylphenyl and mesityl and alkyl groups were tolerated towards the process. Several control experiments have been performed, and the reaction outcomes indicate that the oxidation process is probably concerted with the diamination cyclization, and succinimide generated from NIS‐mediated aminoamidiniumation step promoted the PhI(OAc)2‐mediated oxidation step. The new methodology provides an efficient method for the synthesis of fused tricyclic ureas. 相似文献
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Maotong Xu Andrew R. Jupp Maegan S. E. Ong Katherine I. Burton Saurabh S. Chitnis Douglas W. Stephan 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(17):5763-5767
A series of thirty‐three N,N′‐diaryl, dialkyl, and alkyl‐aryl ureas have been prepared in pyridine or toluene by reaction of silylamines with CO2. This protocol is shown to provide facile access to 13C‐labeled ureas, as well as chiral and macrocyclic ureas. These reactions proceed through initial generation of the corresponding silylcarbamates, which subsequently react with silylamine under thermal conditions to afford the thermodynamically favored urea and disilyl ether. 相似文献
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Per-Anders Enquist 《Tetrahedron letters》2005,46(19):3335-3339
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. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2018,130(20):5955-5959
A facile access to optically active cyclic ureas was developed through palladium‐catalyzed asymmetric hydrogenation of pyrimidines containing tautomeric hydroxy group with up to 99 % ee. Mechanistic studies indicated that reaction pathway proceed through hydrogenation of C=N of the oxo tautomer pyrimidin‐2(1H)‐one, acid‐catalyzed isomerization of enamine–imine, and hydrogenation of imine pathway. In addition, the chiral cyclic ureas are readily converted into useful chiral 1,3‐diamine and thiourea derivatives without loss of optical purity. 相似文献
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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. 相似文献
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Xiang Dong Liu Mika Kimura Atsushi Sudo Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2010,48(23):5298-5305
This report focuses on epoxy‐dicyandiamide (DICY) curing system accelerated by N‐aryl‐N′,N′‐dialkyl urea, aiming at clarifying the accelerating mechanism and the relationship between accelerating effect and molecular structure of the accelerators. Nine N‐aryl‐N′,N′‐dialkyl ureas were synthesized and investigated with measurements of differential scanning calorimetry, thermo gravimetric/differential thermal analysis and NMR spectroscopy. The results revealed that the ureas released the corresponding secondary amines by the thermal dissociation in the presence of epoxide, which led to the formation of tertiary amines that catalyze the addition reaction of DICY to epoxide. Moreover, a tendency that the ureas able to release more compact amines exhibited higher acceleration effects was discovered. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 相似文献
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Daisuke Yamauchi Dr. Takahiro Nishimura Prof. Dr. Hideki Yorimitsu 《Angewandte Chemie (International ed. in English)》2017,56(25):7200-7204
Direct alkylation of a methyl group, on di- and trisubstituted ureas, with terminal alkenes by C(sp3)−H bond activation proceeded in the presence of a hydroxoiridium/bisphosphine catalyst to give high yields of the corresponding addition products. The hydroxoiridium/bisphosphine complex generates an amidoiridium intermediate by reaction with ureas having an N−H bond. 相似文献
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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
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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
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Batey RA Shen M Santhakumar V Yoshina-Ishii C 《Combinatorial chemistry & high throughput screening》2002,5(3):219-232
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. 相似文献
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The calcined Mg‐Al layered double hydroxides (LDHs) with a Mg/Al molar ratio of 3:1 were synthesized and characterized thoroughly by X‐ray diffraction (XRD), temperature‐programmed desorption (TPD) of CO2, and thermogravimetric analysis (TGA). Thus the calcined Mg‐Al LDHs were used as catalyst for the catalytic synthesis of disubstituted ureas from amines and CO2. The effects of reaction time, reaction temperature, pressure, solvent and calcined temperature on activity have been investigated. The results indicated that aliphatic amines, cyclohexylamine and benzylamine can be converted to the corresponding ureas selectively over the calcined Mg‐Al LDHs catalysts with N‐methyl‐2‐pyrrolidone (NMP) as solvent without using any dehydrating regent. The catalyst can be recycled several times with only slight loss of activity. 相似文献
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Andrey V. Smolobochkin Almir S. Gazizov Alexander R. Burilov Michail A. Pudovik 《合成通讯》2013,43(19):2545-2552
In this article, we report the approach to the substituted ureas based on the reaction of 1-(3,3-diethoxypropyl)ureas with phenols. Depending on the nature of the phenol and urea the reaction leads either to diarylpropane and dibenzoxanthene derivatives or calixarenes. The proposed method benefits from mild reaction conditions, high product yields and operational simplicity. 相似文献
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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. 相似文献
20.
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. 相似文献