- Nature of urea-fluoride interaction: Incipient and definitive proton transfer
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1,3-bis(4-nitrophenyl)urea (1) interacts through hydrogen bonding with a variety of oxoanions in an MeCN solution to give bright yellow 1:1 complexes, whose stability decreases with the decreasing basicity of the anion (CH 3COO- > C6H5COO- > H2PO4- > NO2- > HSO4- > NO3-). The [Bu 4N][1·CH3COO] complex salt has been isolated as a crystalline solid and its molecular structure determined, showing the formation of a discrete adduct held together by two N-H...O hydrogen bonds of moderate strength. On the other hand, the F- ion first establishes a hydrogen-bonding interaction with 1 to give the most stable 1:1 complex, and then on addition of a second equivalent, induces urea deprotonation, due to the formation of HF2-. The orange-red deprotonated urea solution uptakes carbon dioxide from air to give the tetrabutylammonium salt of the hydrogencarbonate H-bond complex, [Bu4N][1·HCO 3], whose crystal and molecular structures have been determined.
- Boiocchi, Massimo,Del Boca, Laura,Gomez, David Esteban,Fabbrizzi, Luigi,Licchelli, Maurizio,Monzani, Enrico
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Read Online
- Investigation of active sites using solid state 27Al and 31P MAS NMR in ceramic amorphous aluminophosphate materials prepared from different potassium salts of phosphate for the synthesis of diphenyl urea derivatives
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Ceramic amorphous aluminophosphate (CAmAlP) catalysts were prepared by precipitation method using different phosphate salts of potassium such as KH2PO4, K4P2O7 and K2HPO4 as well as H3PO4. The prepared materials were characterized by PXRD, FT-IR, XPS, SEM, BET Surface area, NH3-TPD, 27Al NMR and 31P NMR analytical methods. The catalytic activity of the materials was checked in the synthesis of diphenyl urea (DPU) from aniline and diethyl carbonate, under refluxing conditions. Further, the general application of the catalysts was tested using various substituted anilines. The recyclability of the catalysts was also studied. Uncertainties in percentage yields were calculated to check the reproducible surface properties. The P-XRD, BET Surface area and NH3-TPD results indicated that the materials were amorphous with mesoporous texture, surface areas and acidities in the range 200–260 m2/g and 0.4–0.7 mmol/g respectively. 27Al NMR studies revealed that Al is present in three different coordination states such as tetrahedral, pentagonal and octahedral. The relative percentages of these Al sites depends on the type of the potassium precursor phosphate salt used. Both tetrahedral and pentagonal Al sites in conjunction with each other represented catalytically active sites. An increase in the pentagonal sites contributed to additional increments to the catalytic activity of CAmAlP. The catalyst prepared from KH2PO4 was found to be the best and demonstrated 96% DPU yield.
- Harish,Kathyayini,Baby, Bindhu,Nagaraju
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- Zinc Powder Catalysed Formylation and Urealation of Amines Using CO2 as a C1 Building Block?
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Transformation of CO2 into valuable organic compounds catalysed by cheap and biocompatible metal catalysts is one of important topics of current organic synthesis and catalysis. Herein, we report the zinc powder catalysed formylation and urealation of amines with CO2 and (EtO)3SiH under solvent free condition. Using 2 molpercent zinc powder as the catalyst, a series of secondary amines, both the aromatic ones and the aliphatic ones, can be formylated into formamides. When primary aromatic amines were used as the substrates, the reactions produce urea derivatives. The electronic and steric effects from the substrates on the formylation and urealation reactions were observed and discussed. The recovery and reusability of zinc powder were investigated, showing the zinc powder can be reused in the formylation reaction without loss of catalytic activity. The analysis on the reactants/products mixture after filtering out the zinc powder showed the zinc concentration in the mixture is low to 1 ppm. The pathways for the formylation and urealation of amines with this catalytic system were also investigated, and related to the different substrates.
- Du, Chongyang,Chen, Yaofeng
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p. 1057 - 1064
(2020/06/30)
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- Method for preparing symmetric urea compound
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The invention provides a novel reaction system for synthesizing a symmetric urea compound by taking CO2 as a carbonylation reagent, wherein Lewis base and hydrosilane are used as accelerators and efficiently enable an aromatic/aliphatic primary amine compound to react with normal-pressure CO2 to generate corresponding symmetric urea compounds containing different functional groups under mild conditions (100 DEG C, diglyme). According to the method, normal-pressure CO2 is used as an environmentally-friendly non-toxic carbonylation reagent, and cheap Lewis base and PMHS (industrial silicon waste) are used as accelerators, so that the use of toxic carbonylation reagents, isocyanate, high-pressure CO2, expensive dehydrating agents and precious metals is avoided, purification and separation ofintermediates are not needed, pure products can be obtained only through simple suction filtration and separation after the reaction is finished, and the method is an efficient and novel synthesis method and has high industrial application value.
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Paragraph 0038-0043; 0110-0115
(2020/03/25)
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- Preparation method of symmetric urea compound
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The invention discloses a preparation method of a symmetric urea compound, which comprises the following steps: by using a hydroxamic acid compound as a raw material, sequentially adding an alkali anda solvent, reacting at 25-50 DEG C for 1-7 hours in an SO2F2 atmosphere, and carrying out aftertreatment on the reaction solution to obtain the symmetric urea compound. According to the invention, cheap, easily available and environment-friendly SO2F2 is used as an accelerant to efficiently promote the generation of an isocyanate intermediate to form a C-N bond. The generation of isocyanate avoids the use of a large amount of halogen or azide dangerous reagents, so that the compound can be used as a green substitute for standard treatment conditions in Curtius rearrangement and Hofmann rearrangement reactions. The amine source in the final product only comes from hydroxylamine, and no additional amine needs to be added, so that the substrate is wide in applicability, and the correspondingsymmetric urea compound can be obtained at a relatively good yield. The operation process is simple, the aftertreatment only needs filtering, and the method is suitable for large-scale preparation.
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Paragraph 0036-0040
(2020/05/30)
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- Concise and Additive-Free Click Reactions between Amines and CF3SO3CF3
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Trifluoromethyl trifluoromethanesulfonate has proved to be an excellent reservoir of difluorophosgene and a promising click ligation for amines in the preparation of urea derivatives, heterocycles, and carbamoyl fluorides under metal- and additive-free conditions. The reactions are rapid, efficient, selective, and versatile, and can be performed in benign solvents, giving products in excellent yields with minimal efforts for purification. The characteristics of the reactions meet the requirements of a click reaction. The use of trifluoromethyl trifluoromethanesulfonate as a click reagent is advantageous over other “CO” sources (e.g., TsOCF3, PhCO2CF3, CsOCF3, AgOCF3, and triphosgene) because this reagent is readily accessible; easy to scale up; and highly reactive, even under metal- and additive-free conditions. It is anticipated that CF3SO3CF3 will be increasingly as important as SO2F2 as a click agent in future drug design and development.
- Song, Hai-Xia,Han, Zhou-Zhou,Zhang, Cheng-Pan
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supporting information
p. 10907 - 10912
(2019/08/02)
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- Spontaneous and direct transformation of N,O-diaryl carbamates into N,N′-diarylureas
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We have discovered a spontaneous reaction of N,O-diaryl carbamates to afford symmetrical N,N′-diarylureas. Optimization of the conditions indicated that N,N-dimethylformamide (DMF) was the best solvent and triethylamine (Et3N) was the best additive for this transformation. The reaction requires the presence of aryl groups on the nitrogen and oxygen atoms of carbamates. Substrates bearing an electron-donating methoxy group on either of the aryl groups reacted slowly under these conditions.
- Yamasaki, Ryu,Honjo, Yutaka,Ito, Ai,Fukuda, Kazuo,Okamoto, Iwao
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p. 880 - 884
(2018/09/10)
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- The: Trans / cis photoisomerization in hydrogen bonded complexes with stability controlled by substituent effects: 3-(6-aminopyridin-3-yl)acrylate case study
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The association of aminopyridine-based acrylic acid and its salt was studied by NMR titration experiments. The AA (acceptor, acceptor) hydrogen-bonding pattern present in the salt forms a complex readily with a DD (donor, donor) hydrogen-bonding pattern of the substituted ureas even in polar and competitive environment. The double carbon-carbon bond in the acrylic acid derivative is subjected to photoisomerization. This is dependent on the association with substituted urea derivatives. The substituent in ureas influences the trans/cis isomerization kinetics and position of the photostationary state. Two mechanisms that influence the photoisomerization were proposed. To the best of our knowledge, the trans/cis photoisomerization influenced by the substituent in such a hydrogen-bonding pattern has not observed previously. It was shown that interaction with urea derivatives causes lowering of the trans-to-cis photoreaction rates.
- Kwiatkowski, Adam,J?drzejewska, Beata,Józefowicz, Marek,Grela, Izabela,O?mia?owski, Borys
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p. 23698 - 23710
(2018/07/13)
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- An efficient synthesis of nitrile, tetrazole and urea from carbonyl compounds
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An efficient conversion of carbonyl compounds (aldehydes and ketones) to nitrile, tetrazole, and urea was developed with the use of a POCl3 and sodium azide mixture using a convergent and microwave method. This is the first report on the direct conversion of ketone to urea. The synthesized compounds were characterized by 1H NMR, 13C NMR, mass and IR spectroscopies and were found to be in agreement with reported compounds.
- Sribalan, Rajendran,Sangili, Arumugam,Banuppriya, Govindharasu,Padmini, Vediappen
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p. 3414 - 3421
(2017/07/13)
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- METHOD OF PRODUCING AROMATIC UREA COMPOUND
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PROBLEM TO BE SOLVED: To provide a method realizing high-yield production of an aromatic urea compound at relatively low temperature without using highly toxic compounds as ingredients and without corrosive or toxic gas by-products.SOLUTION: A method of producing an aromatic urea compound comprises reacting an aromatic compound having one amino group with a compound represented by the formula (1) (X, X=H or Cl) in the presence of a basic salt, an organic base or their mixture as a catalyst, thereby obtaining an aromatic compound having a urea bond.
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Paragraph 0072
(2016/10/07)
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- Antiproliferative effects of novel urea derivatives against human prostate and lung cancer cells; And their inhibition of β-glucuronidase activity
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Twenty-one novel urea derivatives were synthesized and their structures characterized by mass, NMR, IR, and UV spectroscopy. These compounds were evaluated for their antiproliferative profile against human PC-3 (prostate) and NCI-H460 (lung) cancer cell lines. Among them, compound 21 N-(3-nitrophenyl)- N′-(1-phenylethyl)urea was found to be active against both PC-3 (IC 50 ± SEM: 20.13 ± 0.91 μM) and NCI-H460 (GI 50: 22 ± 2.6 μM) cell lines; hence has the potential to be further studied as anticancer agent. These compounds were also investigated for their ability to inhibit urease, β-glucuronidase, and phosphodiesterase enzymes. N-(2,6-Dimethylphenyl)-N′-(4′-nitrophenyl)urea (1) demonstrated 90 % inhibition of β-glucuronidase enzyme (IC50 ± SEM: 3.38 ± 0.043 μM).
- Perveen, Shahnaz,Mustafa, Sana,Qamar, Kehkashan,Dar, Ahsana,Khan, Khalid M.,Choudhary, Muhammad Iqbal,Khan, Ajmal,Voelter, Wolfgang
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p. 1099 - 1113
(2014/03/21)
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- 1,3-disubstituted ureas as antiglycating agents
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Twenty one (21) 1,3-disubstituted urea derivatives were screened for their antiglycating potential and some of them displayed promising activity. Compound N-butyl-N'-(4-nitrophenyl)urea (6) and Nisopropyl-N'-(4-nitrophenyl)urea (18) exhibited excellent activity and could be investigated in search of medicines treating diabetes and associated complications.
- Perveen, Shahnaz,Mustafa, Sana,Khan, Khalid Mohammed,Choudhary, Muhammad Iqbal
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p. 1603 - 1611
(2014/03/21)
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- Discovery of 1-[4-(N-benzylamino)phenyl]-3-phenylurea derivatives as non-peptidic selective SUMO-sentrin specific protease (SENP)1 inhibitors
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We developed 1-[4-(N-benzylamino)phenyl]-3-phenylurea derivative 4 (GN6958) as a non-peptidic selective SUMO-sentrin specific protease (SENP)1 protease inhibitor based on the hypoxia inducible factor (HIF)-1α inhibitor 1 (GN6767). The direct interaction of compound 1 with SENP1 protein in cells was observed by the pull-down experiments using the biotin-tagged compound 2 coated on the streptavidin affinity column. Among the various 1-[4-(N-benzylamino) phenyl]-3-phenylurea derivatives tested, compounds 3 and 4 suppressed HIF-1α accumulation in a concentration-dependent manner without affecting the expression level of tubulin protein in HeLa cells. Both compounds inhibited SENP1 protease activity in a concentration-dependent manner, and compound 4 exhibited more potent inhibition than compound 3. Compound 4 exhibited selective inhibition against SENP1 protease activity without inhibiting other protease enzyme activities in vitro.
- Uno, Masaharu,Koma, Yosuke,Ban, Hyun Seung,Nakamura, Hiroyuki
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p. 5169 - 5173
(2012/09/07)
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- Backscattering Interferometry: An alternative approach for the study of hydrogen bonding interactions in organic solvents
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Intermolecular interactions involving hydrogen bonds are responsible for catalysis and recognition. Traditional methods used to study hydrogen-bonding interactions are generally limited to relatively large volumes and high substrate concentrations. Backscattering Interferometry (BSI) provides a microfluidic platform to study these interactions in nonaqueous media at micromolar to nanomolar concentrations in picoliter volumes by monitoring changes in the refractive index.
- Pesciotta, Esther N.,Bornhop, Darryl J.,Flowers, Robert A.
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supporting information; experimental part
p. 2654 - 2657
(2011/06/25)
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- Catalytic oxidative carbonylation of arylamines to ureas with W(CO) 6/I2 as catalyst
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The oxidative carbonylation of aniline to N,N'-diphenylurea was carried out by using W(CO)6 as the catalyst, I2 as the oxidant, CO as the carbonyl source and 4-(dimethylamino)pyridine (DMAP) as base. The reaction conditions were optimized with respect to different bases, molar ratio of DMAP/iodine, temperature, time, and CO pressure. Various p-substituted arylamines can be converted into the respective symmetrical and unsymmetrical N,N'-disubstituted ureas in moderate to good yields. The reaction demonstrated broad tolerance of functionality.
- Zhang, Li,Darko, Ampofo K.,Johns, Jennifer I.,McElwee-White, Lisa
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experimental part
p. 6261 - 6268
(2011/12/04)
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- Effect of successive increase in alcohol chains on reaction with isocyanates and isothiocyanates
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The reaction of isocyanates and isothiocyanates with long-chain alcohols, e.g. n-hexanol, n-heptanol and n-octanol, exclusively gave N-aryl-O-alkyl carbamates, while N-aryl-O-alkyl carbamates were formed along with symmetrical 1,3-disubstituted ureas and thioureas when the same reactions were carried out with small-chain alcohols at room temperature without using any solvent.
- Perveen, Shahnaz,Yasmin, Arfa,Khan, Khalid Mohammed
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experimental part
p. 18 - 23
(2010/04/23)
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- Co(acac)3/BMMImCl as a base-free catalyst system for clean syntheses of N,N′-disubstituted ureas from amines and CO2
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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.
- Li, Jian,Guo, Xiaoguang,Wang, Liguo,Ma, Xiangyuan,Zhang, Qinghua,Shi, Feng,Deng, Youquan
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experimental part
p. 1534 - 1540
(2010/11/04)
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- Convenient synthesis and biological profile of 5-amino-substituted 1,2,4-oxadiazole derivatives
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We describe herein a convenient straightforward synthesis of 5-amino-substituted 1,2,4-oxadiazoles, upon the reactions of amidoximes with carbodiimides, as well as their further derivatization to acetamides, in good yields. Most of the compounds exhibited in general low interaction with the stable radical 1,1-diphenyl-2-picryl-hydrazyl. Compounds 32 and 39 inhibited significantly soybean lipoxygenase. Selected compounds were screened for their in vivo anti-inflammatory activity using the carrageenin paw edema model and showed significant anti-inflammatory activity (26, 51%). The ability of the compounds to release NO in the presence of a thiol factor has been also investigated.
- Ispikoudi, Maria,Amvrazis, Michalis,Kontogiorgis, Christos,Koumbis, Alexandros E.,Litinas, Konstantinos E.,Hadjipavlou-Litina, Dimitra,Fylaktakidou, Konstantina C.
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experimental part
p. 5635 - 5645
(2011/02/22)
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- An unplanned synthesis of symmetrical 1,3-disubstituted ureas
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When urea derivatives (N-aryl-N′, N'-dialkyl urea) or (N-aryl-N'-alkyl/arvl urea) la-lu react with diethylcarbamyl chloride at 50-60°C symmetrical 1,3-disubstituted ureas 2a-2f were furmed as major products instead of forming ployureas.
- Perveen, Shahnaz,Mustafa, Sana,Khan, Khalid Mohammed
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experimental part
p. 229 - 234
(2011/10/05)
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- Efficient method of synthesis of N,N′-disubstituted ureas/thioureas by a Zinc chloride catalyzed thermal reaction
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Symmetrically N,N'-disubstituted ureas/thioureas were synthesized by heating amines or phenyl hydrazine and urea/thiourea on a preheated hot plate at 80-85C 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.
- Pasha,Madhusudana Reddy
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experimental part
p. 2928 - 2934
(2009/12/03)
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- An 'inside-out' approach to suramin analogues
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An approach to the synthesis of suramin analogues has been realised, which avoids synthetic problems associated with conventional routes. The use of isobutyl ester protecting groups for sulfonic acids was crucial to the success of the strategy, because these were able to be cleanly deprotected with sodium iodide, yielding the sodium salts of the corresponding sulfonic acids.
- McGeary, Ross P.,Bennett, Andrew J.,Tran, Quoc B.,Prins, Johannes,Ross, Benjamin P.
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experimental part
p. 3990 - 3997
(2009/10/09)
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- Process for the preparation of "Urchym" a urease and alpha-chymotrypsin enzyme inhibitory drug
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The present invention relates to the compound N-4-nitrophenyl-N′-4′-nitrophenylurea as a urease and α-chymotrypsin (anti HCV) enzyme inhibitory drug named “Urchym”. N-4-nitrophenyl-N′-4′-nitrophenylurea is prepared and screened for their urease and α-chymotrypsin inhibition effects, the said compound, showed strong urease inhibition (IC50=1.25 μM). We found, that the same compound is also an efficient α-chymotrypsin inhibitor having an IC50 value of 3.15 μM.
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Page/Page column 1-2
(2008/12/08)
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- PROCESS FOR PREPARING GEMCITABINE AND ASSOCIATED INTERMEDIATES
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Provided is a process for preparing gemcitabine and intermediates useful in the production of gemcitabine. Exemplary intermediates include mixtures of D-erythro and D-threo diastereomers of ethyl 3-(N-carbamoyloxy)-2,2-difluoro-3-(2,2-dimethyldioxolan-4-yl)propionates, from which a preferred isomer can be separated, e.g., by selective crystallization, in accordance with the invention. Also provided are novel alkyl (D-erythro)-3-hydroxy-2,2-difluoro-3-(2,2-dimethyldioxolan-4-yl)propionate intermediates, and novel ribo lactones, which can be used for producing gemcitabine.
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Page/Page column 20-21
(2008/06/13)
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- A rapid microwave assisted synthesis of N, N′-diarylureas under solvent-free condition
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A novel microwave assisted phosgene-free synthesis of N,N′- diarylureas under solvent-free conditions has been described.
- Sarveswari,Raja
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p. 546 - 547
(2007/10/03)
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- Efficient synthesis of N,N′-disubstituted ureas/thioureas catalyzed by iodine
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Iodine is an efficient catalyst for the synthesis of symmetrically N,N′-disubstituted ureas/thioureas by heating respective amines or phenyl hydrazine and urea/thiourea on a preheated hot plate at 90-95°C, under solvent-free conditions. The yields are excellent, and the reactions go to complete within 5-10 min. Copyright Taylor & Francis Group, LLC.
- Pasha,Jayashankara
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p. 1787 - 1793
(2007/10/03)
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- Chemistry of polyhalogenated nitrobutadienes, 2: Synthesis of N-tetrachloroallylidene-N′-arylhydrazines by a formal synproportionation reaction
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The reaction of 2-nitropentachlorobuta-1,3-diene with a variety of anilines substituted with electron-withdrawing groups generates, contrary to expectations, N-tetrachloroallylidene-N′-arylhydrazines instead of 1,1-bisaminated substitution products. The imidoyl-type chlorides are capable of undergoing nucleophilic substitution with amines or hydrides. The resulting compounds should exhibit physiological activity, especially for use in crop science. Georg Thieme Verlag Stuttgart.
- Zapol'skii, Viktor A.,Nutz, Eva,Namyslo, Jan C.,Adam, Arnold E. W.,Kaufmann, Dieter E.
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p. 2927 - 2933
(2008/02/05)
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- CeCl3 · 7H2O-KI-catalyzed, environmentally friendly synthesis of N,N′-disubstituted ureas in water under microwave irradiation
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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. Copyright Taylor & Francis, Inc.
- Li, Zheng
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p. 2325 - 2331
(2007/10/03)
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- Expeditious method for synthesis of symmetrical 1,3-disubstituted ureas and thioureas
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Symmetrical 1,3-disubstituted ureas and symmetrical thioureas have been synthesized from corresponding isocyanates, diisocyanates, and isothiocyanates by a new versatile, simple, and quick method in the presence of tertiary amines at room temperature. The method under discussion has several advantages over the existing techniques, as it is simple to carry out, does not require complicated equipment, has a simple workup, and does not use expensive chemicals. Moreover, the yields are almost quantitative. This method has potential in commercial applications. Copyright Taylor & Francis, Inc.
- Perveen, Shahnaz,Abdul Hai, Syed M.,Khan, Rashid A.,Khan, Khalid Mohammed,Afza, Nighat,Sarfaraz, Tahira B.
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p. 1663 - 1674
(2007/10/03)
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- ULTRAMINE: A high-capacity polyethylene-imine-based polymer and its application as a scavenger resin
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The synthesis of a novel high-loading polyethylene-imine resin (ULTRAMINE) is described, and its application as a scavenger resin in various acylation reactions is demonstrated. The inverse suspension polymerization technique was used for the synthesis of well-defined spherical polymer beads. Polymer beads with different cross-linking densities were synthesized according to the degree of acryloylation of the polyethylene-imine polymer. The resin was characterized by various spectroscopic techniques. The size, shape, and morphological features of the resin were demonstrated by microscopy. The resin showed excellent swelling properties in both polar and nonpolar solvents. The chemical stability of the resin in various reagents and solvents was investigated and monitored by IR spectroscopy. The mechanical stability of the beads was determined by a single-bead compressive experiment. The ULTRAMINE beads can be used as an excellent scavenger for excess acylating reagent, as demonstrated for a variety of reactions. UL-TRAMINE-red resin was derived from ULTRAMINE through exhaustive reduction of the amide carbonyl groups to yield an all-amine resin.
- Roice, Michael,Christensen, Soren F.,Meldal, Morten
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p. 4407 - 4415
(2007/10/03)
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- Palladium-catalyzed arylation of ureas
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Urea arylation with aryl halides in the presence of catalyst precursor Pd2dba3-CHCl3/Xantphos and Cs 2CO3 in dioxane at 100°C affords symmetrical N,N′-diarylureas in 64-92% yield. With the same cataly
- Artamkina,Sergeev,Beletskaya
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p. 538 - 545
(2007/10/03)
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- Palladium-catalyzed reaction of aryl halides with ureas
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A new method for the palladium-catalyzed arylation of ureas is described. The coupling reaction of urea and phenylurea with aryl halides containing electron-withdrawing groups in the p-position in dioxane in the presence of 0.5-1.0 mol% of Pd2dba3·CHCl3, Xantphos and Cs2CO3 as a base gives N,N′-diarylureas in yields of 64-92%.
- Artamkina, Galina A.,Sergeev, Alexey G.,Beletskaya, Irina P.
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p. 4381 - 4384
(2007/10/03)
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- NEW ROUTE FOR THE SYNTHESIS OF SYMMETRICAL DIARYLUREA
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Several esters of aryl carbamic acid were thermally dissociated into symmetrically diarylurea in high yields.The electronic effect and position of the substitution in the aryl groups as well as the role of the alkyl groups on the thermal reaction are discussed.
- Hassan, Alaa A.,Mourad, Aboul-Fetouh E.
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p. 397 - 404
(2007/10/02)
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- A new route for the synthesis of symmetrical diarylureas
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Several esters of arylcarbamic acid have been thermally dissociated into symmetrical diarylureas in high yields.The electronic effect and position of substitution in the aryl groups as well as the role of alkyl groups on thermal reaction have been discussed.
- Hassan, Alaa A,Mourad, Aboul-fetouh E
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p. 277 - 279
(2007/10/02)
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- Hydrogen bond directed cocrystallization and molecular recognition properties of diarylureas
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The hydrogen bond directed molecular recognition properties of a series of diarylurea (DAU) compounds have been studied using cocrystallization to probe hydrogen bond donor and acceptor selectivity of the host and guest molecules. Diarylureas with meta-substituted electron-withdrawing groups on the aryl rings are capable of forming cocrystal complexes with a wide variety of hydrogen bond acceptors. One particular DAU, 1,3-bis(m-nitrophenyl)urea, behaves primarily as a proton donor, one of the few organic molecules known to have this property. Its hydrogen bond accepting ability is drastically reduced, possibly because of two very weak CH?O interactions occurring in response to the presence of guest acceptor molecules and effectively negating the powerful proton-accepting ability of the urea carbonyl group. Only DAU compounds with meta-substituted electron-withdrawing groups have this property. The crystal structures of four DAU compounds and six of their cocrystal structures are reported. In addition, 19 other DAU cocrystals were prepared and characterized by chemical and spectroscopic means, and their hydrogen bond patterns were assigned based on spectroscopic analogies to those with known crystal structures. From this data hydrogen bond rules for diarylureas have been derived for use in predicting hydrogen bond patterns in related structures.
- Etter, Margaret C.,Urba?czyk-Lipkowska, Zofia,Zia-Ebrahimi, Mohammad,Panunto, Thomas W.
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p. 8415 - 8426
(2007/10/02)
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- N- and O-Alkylations of Nitro-Substituted 1,3-Diphenylureas: Preparations of Propellant Stabilizer Derivatives
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A procedure has been developed for the N-ethylation and methylation of 1,3-diphenylureas, ArNRCONHAr' (R=H, Me or Et), through treatment with sodium hydride and iodoalkane in dimethylformamide.The reaction was general, provided that the aniline to be alkylated was substituted with no more than one nitro group.ArRNCONR'Ar' derivatives prepared were: R = R'= Et (and Me); Ar = phenyl, Ar' = 2-nitrophenyl and 4-nitrophenyl; Ar = 2-nitrophenyl, Ar' = 2-nitrophenyl and 4-nitrophenyl; Ar = Ar' = 4-nitrophenyl.Two mixed derivatives were also prepared: R = Et, R' = Me, Ar = phenyl, Ar' = 2-nitrophenyl and 4-nitrophenyl.O-Alkylated isourea products were obtained in the reactions of 1-(2,4-dinitrophenyl)-3-(2-nitrophenyl)urea and 1-(2,4-dinitrophenyl)-3-(4-nitrophenyl)urea.The use of potassium carbonate as the base led to apparently exclusive O-alkylation of 1,3-bis(2-nitrophenyl)urea although the reaction was not general. 1-(2,4-Dinitrophenyl)-1,3-diethyl-3-phenylurea was prepared by using silver oxide and obtained as a mixture with the isourea.Many of the compounds prepared are important nitro derivatives of the propellant stabilizers, ethyl and methyl centralite.
- Curtis, Neville J.
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p. 585 - 595
(2007/10/02)
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- Nucleophilic Substitutions at Carbonic Acid Derivatives. XX. Aminolysis of Bis(trichlormethyl)carbonate
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The rate constants for the two steps of the reaction of bis(trichlormethyl)carbonate with substituted anilines have been determinated by conductivity measurements.The first relatively fast step of the reaction is the nucleophilic attack of the amine to the bis(trichloromethyl)carbonate leading to trichloromethylurethane through a six or four centers transition state in wich the carbon-nitrogen bond is formed parallel with the transfer of the proton.In this reaction a phosgene molecule is also produced, which reacts very fast with amine to form a N,N'-diarylurea.The s econd, much slower step, is the nucleophilic attack of the amine to the trichloromethylurethane.Through a similar transition state in which the proton transfer has even a higher importance, a N,N'-disubstituted urea and an other molecule of phosgene are formed.
- Cotarca, Livius,Bacaloglu, R.,Csunderlik, C.,Marcu, N.,Tarnaveanu, A.
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p. 1052 - 1062
(2007/10/02)
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- Intramolecular Reaction Between Nitro and Carbodi-imide Groups; A New Synthesis of 2-Arylbenzotriazoles
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1-(2-Nitrophenyl)-5-phenyltetrazole (5b) decomposes when heated to give nitrogen, carbon dioxide, and 2-phenylbenzotriazole (6) in high yield.This new molecular rearrangement proceeds via 2-nitrophenyl(phenyl)carbodi-imide (8).Other precursors of this carbodi-imide, i.e. oxadiazolone (10), oxadiazolethione (11), oxathiadiazole 2-oxide (12), and the aminimide (16), and carbodi-imide itself, all give 2-phenylbenzotriazole (6) on thermolysis, the last three in high yield.This reaction is general for diarylcarbodi-imides with an ortho nitro group, and their precursors, and it provides a useful new route to 2-arylbenzotriazoles.A sequence of electrocyclic ring closing and opening reactions (Scheme 5) is proposed as the mechanism of this process.The key intermediate, 2-phenyl-1,2,4-benzotriazin-3-one 1-oxide (19) has been isolated from a careful thermolysis of (12) in toluene; in solution it is in reversible equlibrium with the ring-opened form (20).This new nitro-carbodi-imide group interaction has been extended to the more stable nitrobiphenyl(phenyl)carbodi-imide (25) and nitronaphthyl(phenyl)carbodi-imide (24) which, on flash vacuum pyrolysis, give benzimidazophenanthridine (29) and benzindazole 1-oxide (32) respectively, in new rearrangements.
- Houghton, Peter G.,Pipe, David F.,Rees, Charles W.
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p. 1471 - 1480
(2007/10/02)
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- Novel Bis as Antitrypanosomal Agents
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A series of novel 1,1'-(4,1-phenylene)bis was prepared and evaluated for activity against Trypanosoma rhodesiense in mice.The importance of the bis structure and the nature of the spacer between the two phenyl rings for optimal activity have been revealed.The potent parenteral activity of several analogues within this series as well as preliminary indication of oral activity lends encouragement to further development of this structural class.
- Turner, William R.,Werbel, Leslie M.
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p. 1728 - 1740
(2007/10/02)
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- SUBSTITUENT EFFECTS ON HYDROLYTIC STABILITY AND HERBICIDAL ACTIVITY OF 3-ARYLIMIDAZOLIDINE-2,4-DIONES
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Twenty-one derivatives of imidazolidine-2,4-dione have been prepared by reactions of substituted amino acids with aryl isocyanates in aqueous medium.Pre- and post-emergent herbicidal activities of all the compounds have been tested, and stability of five derivatives has been followed in aqueous medium within the pH range from 7.6 to 13.0.The highest pre-emergent herbicidal activity has been found with the derivatives XI-XVI which inhibit the growth of most indicator plants at the doses of 1.6 kg/ha.The derivatives studied are relatively stable in aqueous medium, the hydrolysis half-life of the compound XI being 9 days at pH 8.
- Cegan, Alexandr,Vecera, Miroslav
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p. 1521 - 1528
(2007/10/02)
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- FACILE CONVERSION OF 1,3-DISUBSTITUTED THIOUREAS TO THE CORRESPONDING UREAS BY SUPEROXIDE RADICAL ANION (O2.-) IN DIMETHYL SULFOXIDE
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Treatment of 1,3-disubstituted thioureas with superoxide radical anion (O2.-) at 20 deg C in dimethyl sulfoxide resulted in the formation of 1,3-disubstituted ureas in excellent yields.The desulfurization appears to proceed by the formation of peroxy-sulfur intermediates such as peroxy-sulfenate, -sulfinate and/or -sulfonate.
- KIM, Yong Hae,YON, Gyu Hwan,KIM, Hyung Jin
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p. 309 - 312
(2007/10/02)
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- Process for the preparation of N-aryl-N'-(mono- or di substituted)-urea derivatives
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The invention relates to a new method for the preparation of N-aryl-N'-(mono- or disubstituted)-urea derivatives having the general formula (I), STR1 wherein Aryl is an optionally substituted phenyl group, and R1 and R2 each stand for an optionally substituted alkyl, cycloalkyl, alkoxy or phenyl group, or R1 and R2 may form, together with the adjacent nitrogen atom, a nitrogen-containing heterocyclic group which may contain a further hetero atom, or one of R1 and R2 may also stand for hydrogen, with the proviso that if one of R1 and R2 is an optionally substituted phenyl group, the other may represent only hydrogen atom or an optionally substituted alkyl or alkoxy group, by reacting a carbamate of the general formula (II) with an amine of the general formula (III), or a carbamate of the general formula (IV) with an amine of the general formula (V), wherein R1, R2 and Aryl are as defined above and X is a lower alkoxy, phenoxy or substituted phenoxy group, in the presence of a tertiary amine catalyst. According to the invention a tertiary alkylamine containing altogether at least 6 carbon atoms and minimum one alkyl chain with at least 4 carbon atoms or a mixture of such tertiary alkylamines is applied as catalyst.
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- PREPARATION AND PROPERTIES OF SOME CITRULLINE p-NITROANILIDE DERIVARIVES FOR POSSIBLE USE AS PROTEASE SUBSTRATES
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A number of citrulline p-nitroanilides have been synthesised as potential substrates for proteolytic enzymes.Nα-Benzyloxycarbonyl-L-citrulline p-nitroanilide, a key starting material, was prepared by the phosphoazo method.During this reaction, depending on the conditions, lactam formation and decarbamoylation took place.It is probable that decarbamoylation took place subsequent to the lactamisation step.The derivatives prepared included some protected tripeptide nitroanilides, benzyloxycarbonylglycyl-L-prolyl-L-citrulline p-nitroanilide, benzyloxycarbonyl-D-phenylalanyl-L-prolyl-L-citrulline p- nitroanilide, benzyloxycarbonylglycyl-L-phenylalanyl-L-citrulline p-nitroanilide, methyloxycarbonylglycyl-L-phenylalanyl-L-citrulline p-nitroanilide and a protected tetrapeptide, benzyloxycarbonylglycyl glycyl-L-phenylalanyl-L-citrulline p-nitroanilide.Preliminary results have indicated that citrulline p-nitroanilides are far more susceptible to hydrolysis by plant thiol enzymes such as papain, ficin and bromelain than by mammalian proteases.
- Gray, C. J.,Boukouvalas, J.,Barker, S. A.
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p. 1465 - 1470
(2007/10/02)
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- Substrate for the quantitative determination of proteolytic enzymes
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A substrate for the quantitative determination of enzymes in human and mammal body fluids as well as in animal cell extracts and glandular venoms of cold-blooded animals, which has the structure wherein R1 represents hydrogen or a blocking acyl or sulfonyl group, R2 represents an aromatic hydrocarbon group which may carry substituents and X represents arginyl or lysyl, --NH--R2 being a chromogenic or fluorescent group capable of yielding a split product NH2 --R2 the quantity of which can be measured by photometric, spectrophotometric or fluorescence-photometric methods.
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