- Chloromethylated polystyrene immobilized ruthenium complex of 2-(2-pyridyl)benzimidazole catalyst for the synthesis of bioactive disubstituted ureas by carbonylation reaction
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Polymer supported transition metal complex catalysts have numerous applications as heterogeneous catalysts due to their ease of synthesis and commercial availability. Ru-Py-Merf was synthesized by anchoring 2-(2-pyridyl)benzimidazole to the polymer matrix, followed by loading of ruthenium salt. This Ru-Py-Merf material was thoroughly characterized by FTIR spectroscopy, UV-vis absorption spectroscopy, FE-SEM analysis, EDAX analysis, CHN analysis, AAS spectroscopy and TGA. Ru-Py-Merf showed excellent catalytic activity in the synthesis of symmetric and asymmetric disubstituted ureas by reductive carbonylation of nitrobenzenes and anilines. The as-synthesized Ru-Py-Merf catalyst is entirely heterogeneous in nature, thermally stable and can be easily reused up to six times.
- Dey, Tusar Kanto,Ghosh, Kajari,Basu, Priyanka,Molla, Rostam Ali,Islam, Sk. Manirul
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- Synthesis and architecture of polystyrene-supported Schiff base-palladium complex: Catalytic features and functions in diaryl urea preparation in conjunction with Suzuki-Miyaura cross-coupling reaction by reductive carbonylation
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This work represents an efficient and unique phosphine-free approach for the polystyrene embedded Schiff-base palladium catalyzed diaryl urea synthesis and Suzuki-Miyaura cross-coupling reaction by reductive carbonylation process. The careful instrumental investigations with FE-SEM, TEM, EDAX, TGA, UV–Vis, FTIR, AAS, and elemental analysis precisely characterized the developed heterogeneous catalyst. Reaction parameters, like catalytic natures, starting materials, reaction environment, and solvent were examined sequentially. The present work has been adequately addressed to account for the generation and characterization of a new polymer bound Pd-catalyst and using it in the synthesis of diaryl ureas and diaryl ketones, with no substantial decay of catalytic activity.
- Basu, Priyanka,Riyajuddin, Sk,Dey, Tusar Kanto,Ghosh, Aniruddha,Ghosh, Kaushik,Islam, Sk Manirul
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- Reaction of β-Nitro Enamines with Isocyanates, Isothiocyanates and Dimethyl Acetylenedicarboxylate
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β-Nitro enamines (1) reacted with isocyanates and isothiocyanates to give β-(substituted carbamoyl) and β-(substituted thiocarbamoyl) β-nitro enamines, respectively.The reaction of 1 with benzoyl isothiocyanate gave β-(benzoylthiocarbamoyl) β-nitro enamines (8) and/or a mixture of 8 and 4(1H)-pyrimidinethione derivatives (9), which were cyclization products of 8.The isolated 8 afforded the corresponding 9 in high yields upon heating in DMF.The reaction of 1 with dimethyl acetylenedicarboxylate gave cycloadducts (12) and/or a mixture of 12 and δ-nitro dienamino diesters (13) which were ring cleavage products of 12.Compounds 12 afforded 13 upon heating in toluene or xylene.
- Tokumitsu, Takao
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- Splitting a Substrate into Three Parts: Gold-Catalyzed Nitrogenation of Alkynes by C-C and C≡C Bond Cleavage
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A gold-catalyzed nitrogenation of alkynes for the synthesis of carbamides and amino tetrazoles through C-C and C≡C bond cleavages is described. A diverse set of functionalized carbamide and amino tetrazole derivatives were selectively constructed under mild conditions. The chemoselectivity can be easily switched by the selection of the acid additives. The reaction is characterized by its broad substrate scope, direct construction of high value products, easy operation under air, and mild conditions at room temperature. This chemistry provides a way to transform alkynes by splitting the substrate into three parts.
- Qin, Chong,Su, Yijin,Shen, Tao,Shi, Xiaodong,Jiao, Ning
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p. 350 - 354
(2016/01/25)
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- Microwave-assisted synthesis of symmetrical and unsymmetrical N,N 0-disubstituted thioureas and ureas over MgO in dry media
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Under mild microwave irradiation conditions a variety of symmetrical and unsymmetrical A,N′-disubsti-tuted thioureas and ureas were prepared via the reaction of Af-monosubstituted hydroxylamines with isocyanate and isothiocyanate derivatives over MgO under solvent-free conditions. This new method afforded satisfactory results with good yields, short reaction time, and simplicity in the experimental procedure.
- Valizadeh, Hassan,Dinparast, Leila
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experimental part
p. 251 - 254
(2012/07/01)
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- The vinyl moiety as a handle for regiocontrol in the preparation of unsymmetrical 2,3-aliphatic-substituted indoles and pyrroles
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Rho-Rho-Rho your boat: A rhodium catalyst effects the regioselective oxidative coupling of enynes with N-aryl ureas (X=NR2) and N-vinylacetamides (X=C(O)Me), affording the corresponding 2-alkenylindoles and 2-alkenylpyrroles in good yield. Simple hydrogenation delivers the C2/C3-aliphatic-substituted indole or pyrrole (see scheme).
- Huestis, Malcolm P.,Chan, Lina,Stuart, David R.,Fagnou, Keith
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supporting information; experimental part
p. 1338 - 1341
(2011/04/21)
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- Intramolecular hydrogen bonding in medicinal chemistry
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The formation of intramolecular hydrogen bonds has a very pronounced effect on molecular structure and properties. We study both aspects in detail with the aim of enabling a more rational use of this class of interactions in medicinal chemistry. On the basis of exhaustive searches in crystal structure databases, we derive propensities for intramolecular hydrogen bond formation of five- to eight-membered ring systems of relevance in drug discovery. A number of motifs, several of which are clearly underutilized in drug discovery, are analyzed in more detail by comparing small molecule and protein-ligand X-ray structures. To investigate effects on physicochemical properties, sets of closely related structures with and without the ability to form intramolecular hydrogen bonds were designed, synthesized, and characterized with respect to membrane permeability, water solubility, and lipophilicity. We find that changes in these properties depend on a subtle balance between the strength of the hydrogen bond interaction, geometry of the newly formed ring system, and the relative energies of the open and closed conformations in polar and unpolar environments. A number of general guidelines for medicinal chemists emerge from this study
- Kuhn, Bernd,Mohr, Peter,Stahl, Martin
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supporting information; experimental part
p. 2601 - 2611
(2010/08/05)
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- Flash vacuum pyrolysis of 1,2,5-oxadiazole 2-oxides and 1,2,3-triazole 1-oxides
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The flash vacuum pyrolysis (FVP, 450-600 °C/10-3 mmHg) of 3,4-diaryl- and 3,4-dialkyl-1,2,5-oxadiazole 2-oxides (furoxans) has been investigated. In all cases the 1,2,5-oxadiazole ring cleaved cleanly at O(1)-N(2) and C(3)-C(4) to afford two nitrile oxide fragments, which were trapped in high yield (75-97%) as their isoxazoline cycloadducts by reaction with alk-1-enes. At higher temperatures (700-800 °C) isocyanates were formed as by-products. The dimerisation of acetonitrile oxide to dimethylfuroxan was followed by 1H NMR spectroscopy, and the rate constant for the 2 nd order reaction determined. The furoxans were converted into isocyanates in good yield (61-95%) by FVP, followed by sulfur dioxide-mediated isomerisation of the resulting nitrile oxides. 2,4,5-Trisubstituted-1,2,3- triazole 1-oxides showed greater thermal stability, but at 700-800 °C decomposition of the 4,5-dimethyl compound 25b lead to 1,2-di(5-methyl-2-phenyl- 1,2,3-triazol-2-yl)ethane as the major product; attempts to trap acetonitrile oxide were unsuccessful. ARKAT USA, Inc.
- Mitchell, William R.,Paton, R. Michael
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experimental part
p. 34 - 54
(2011/02/21)
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- Synthesis and anticonvulsant activity of new N-1′,N-3′-disubstituted-2′H,3H,5′H-spiro-(2-benzofuran-1,4′-imidazolidine)-2′,3,5′-triones
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Thirteen new N-1′,N-3′-disubstituted-2′H,3H,5′H-spiro-(2-benzofuran-1,4′-imidazolidine)-2′,3,5′-triones were synthesized and their pharmacological activity determined with the objective to better understand their SAR for anticonvulsant activity. The anticonvulsant effects of these compounds were evaluated by standard pentylenetetrazol (scPTZ test) and maximum electroshock seizure (MES test) models in mice. Most of the compounds showed ability to protect against the pentylenetetrazol-induced convulsions. Compound 3o (the N-1′-p-nitrophenyl, N-3′-ethyl derivative) in the N-1′-aryl, N-3′-alkyl disubstituted series exhibited maximum activity with ED50 of 41.8 mg/kg in scPTZ convulsion model.
- Patel, Hardik J.,Sarra, Joe,Caruso, Francesco,Rossi, Miriam,Doshi, Utkarsh,Stephani, Ralph A.
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p. 4644 - 4647
(2007/10/03)
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- Synthesis and characterisation of platinum(II) ureylene complexes, and the X-ray structure of [Pt{PhNC(O)NAd}(COD)] (Ad = 1-adamantyl, COD = 1,5-cyclo-octadiene)
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Reaction of [PtCl2(COD)] or cis-[PtCl2(PPh3)2] with a range of mono-and di-substituted ureas, together with urea itself, and an excess of silver(I) oxide gives ureylene complexes 3 and 4 containing the Pt-N-C(O)
- Dinger, Maarten B.,Henderson, William,Nicholson, Brian K.,Wilkins, Alistair L.
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p. 303 - 312
(2007/10/03)
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- Ureas from N-Chloroamidines; An Aza-Analogous Hofmann Degradation
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N-Chlorination and subsequent treatment with alkali of suitably substituted benzamidines yields ureas with phenyl or alkyl migration.Under the same conditions, 2-iminopyrrolidine is converted into 2-oxohexahydropyrimidine with ring enlargement.
- Sonnenschein, Helmut,Schmitz, Ernst
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p. 443 - 444
(2007/10/02)
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- Reactions of N- or N'-Blocked N-acylureas with Amines
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In order to make reactions of N-acylureas with amines more selective N- or N'-blocked derivatives were prepared.Their fragmentation was examined.
- Schweim, Harald G.
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p. 430 - 437
(2007/10/02)
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- PREPARATION AND PROPERTIES OF 3-ALKYL-i-ARYLNITROSOUREAS AND RELATED COMPOUNDS
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Nitrosation of 3-alkyl-1-arylureas was investigated with sodium nitrite in 99percent formic acid or with isoamyl nitrite in chloroform.The preparation of 3-alkyl-1-aryl-1-nitrosoureas was effectively performed by using isoamyl nitrite in the absence of acids, since the 1-nitrosoureas were isomerized to the 3-nitroso isomers by acids.The carbon-13 nuclear magnetic resonance and infrared spectral properties of the products were examined and their structural features are discussed.It was found that 3-alkyl-1-aryl-1-nitrosoureas decomposed to form alkyl isocyanates and 3-alkyl-1-(2-nitroaryl)ureas in carbon tetrachloride. 1,3-Rearrangement and transnitrosation also took place in this solvent.Keywords - 3-alkyl-1-arylnitrosourea; 3,3-diethyl-1-tolyl-1-nitrosourea; N-nitrosourea; nitrosation; 1,3-rearrangement; isomerization; transnitrosation; nitration
- Tanno, Masayuki,Sueyoshi, Shoko
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p. 1360 - 1371
(2007/10/02)
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- Photoextrusion of Nitrogen from 1,4-Dihydro-1-phenyl-5H-tetrazol-5-ones and -thiones. Benzimidazolones and Carbodiimides
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Alkylation of 1-phenyltetrazolone 10a with 2-cyclohexen-1-yl bromide followed by dehydrogenation with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone permits introduction of a phenyl group at N-4 of the tetrazole ring via the sequence 10a -> 10f -> 10g.The photoextrusion of molecular nitrogen from the (N-4)-substituted 1-phenyltetrazolones, 10a (hydrogen), 10b (methyl), 10d,e (propenyl), and 10g (phenyl) produces essentially quantitative yields of the corresponding benzimidazolones 14a,b,d,e,g.On irradiation of the 1-phenyltetrazolethiones 8b,f,g the carbodiimides 22b,f,g are obtained together with molecular nitrogen and sulfur, while 8a affords phenylcyanamide (25).In contrast to the thermolysis, which is known to give 2-(methylamino)benzothiazole (21b), photolysis of the (phenylimino)-1,2,3,4-thiatriazole 24, an isomer of methylphenyltetrazolethione 8b, also yields molecular nitrogen, sulfur, and methylphenylcarbodiimide (22b).
- Quast, Helmut,Nahr, Uwe
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p. 526 - 540
(2007/10/02)
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- Kinetics and Mechanism of Hydrolysis of 4-Phenylallophanates
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The kinetics of hydrolysis of aryl and alkyl 4-phenylallophanates to phenyl urea and phenol or alcohol are studied.Acid-base catalysis, deuterium solvent isotope effects, and entropy of activation provide good evidence for a changeover in mechanism from E1cB for aryl allophanates to BAc2 for alkyl esters.The parameters of Hammett and Yukawa-Tsuno relationships for aryl esters and the non-linear Bronsted correlation with the pKa values of the leaving groups are in good agreement with the proposed mechanism.
- Sabbagh, Mohamed Mowafak Al,Calmon, Michelle,Calmon, Jean-Pierre
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p. 1233 - 1238
(2007/10/02)
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- INFRARED AND 1H-NMR STUDY OF MOLECULAR CONFORMATION OF SOME N,N'-ARYLALKYLUREAS
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The 270 MHz 1H-NMR and IR spectra of several N,N'-arylalkylureas are analyzed in terms of their conformational properties.For most systems, the -NHCONH- group adopts a less energetic trans-cis conformation which is stabilized by unsymmetric intramolecular hydrogen bonding of lower polarizability, in contrast ot other N,N'-disubstituted ureas which are predominantly found in the trans-trans form.The influence of the N-substituent on hydrogen bonding and molecular conformation is emphasized.
- Sudha, L. V.,Sathyanarayana, D. N.
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- Reactivite de cyclo- et tri-germazanes: Mise en evidence de la participation de germyleneamines dans des reactions d'insertion-elimination
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Cyclogermazanes (R2GeNR')n (n=2,3), oligomers of germyleneamines, R2Ge=NR', are obtained through aminolysis or amonolysis of Ge-Cl bonds, by intramolecular transamination, or by reaction between chlorogermanes and dilithium amides.The oligomerization degree (n=2,3) is strongly dependent on the nature of the substituents bonded to nitrogen or germanium.Cleavage reactions by bifunctional protic reagents such as diols, dithiols, aminoalcohols, aminothiols and aminoacids have been studied and lead to the corresponding five-membered germa heterocycles resulting from the cleavage of two consecutive Ge-N bonds.Insertion reactions of either heterocumulenes and insaturated dipoles such as RNCO, RNCS, CO2, CS2, PhCHO or oxirane lead to ring expansion.Compounds resulting from diaddition of isocyanates and isothiocyanates to cyclogermazanes, decompose with formation transient germyleneamines which have been characterized by means of their 1,2-cycloaddition reactions with iso- or isothio-cyanates leading to unsatble diazagermetidiones, (or thiones).Similarly, adducts between cyclogermazanes and aldehydes , CO2, CS2 lead to cyclogermoxanes or cyclogermathianes through the corresponding germanones or germathiones. 1,3-Dipoles such as nitrones react with with cyclogermazanes at temperatures around 150 degree C to give unstable 1,3,5,2-oxadiazagermolidines.The reactivity of cyclogermazanes is enhanced in the presence of triethylamine or hexamethylphosphotriamide.The possibility of participation in the latter reactions for the monomeric germyleneamine R2Ge=NR' resulting from the equilibrium cyclogermazane germyleneamine is discussed.
- Lacrampe, G.,Lavayssiere, H.,Riviere-Baudet, M.,Satge, J.
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- Nouvelles syntheses de phenyl-4 allophanates
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The synthesis of eighteen alkyl or phenyl 4-phenylallophanates is described.The classical methods used for the preparation of allophanates - namely, condensation between an isocyanate and a carbamate, reaction between a urea and a carbonate, desulphurization of 3-thioallophanic acid esters - proved to be unsuitable for the synthesis of 4-phenylallophanic acid phenyl esters.Variously substituted 4-phenylallophanates can be obtained by reacting a chloroformate with a phenylurea in the presence of pyridine, which promotes the transfer of the carboxylate group.The occurence of electrondonating substituents, such as CH3, at the nitrogen atom receiving the carboxylate group promotes the reaction.The low yields observed for aliphatic esters can be accounted for by the instability of the alkyl chloroformate-pyridine complex.The structures of the derivatives synthesized was corroborated by the analysis of their n.m.r. and u.v. spectra. Non-commercial phenyl chloroformates were prepared by reacting phosgene with a sodium phenolate in the presence of anhydrous benzene.
- Al Sabbagh, Mohamed Mowafak,Calmon, Michelle,Calmon, Jean-Pierre
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- SALT EFFECT IN HYDROLYSIS OF 3-ACYL-1,3-DIPHENYLTRIAZENES
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Rate constants of non-catalyzed hydrolysis of 3-acetyl-1,3-diphenyltriazene (I) and 3-(N-methyl-carbamoyl)-1,3-diphenyltriazene (II) have been measured in the presence of salts (ammonium chloride, potassium chloride, lithium chloride, sodium chloride and bromide, ammonium sulphate, potassium sulphate, lithium sulphate, sodium sulphate, and zinc sulphate) within broad concentration ranges.Temperature dependence of the hydrolysis of the substrates studied has been measured in the presence of lithium sulphate within temperature range 20 deg to 55 deg C.The results obtained have been interpreted by mechanisms of hydrolysis of the studied substances.
- Ludwig, Miroslav,Pytela, Oldrich,Vecera, Miroslav
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p. 3104 - 3109
(2007/10/02)
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- REACTION OF ACTIVATED AZIRIDINES WITH AMINES
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The reactions of 1-alkoxycarbonylaziridines, 1-(phenylaminocarbonyl)aziridine, and 1-arylsulfonylaziridines with ammonia and amines were investigated.It was shown that the opening of the aziridine ring in a number of cases is accompanied by aminolysis of the alkoxycarbonyl group.The dependence of the ratio of ring opening and aminolysis products on the structure of the amines is discussed.
- Baranov, S. V.,Mochalin V. B.
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p. 951 - 953
(2007/10/02)
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- Conformational Preferences in Alkylnitrosoureas
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The spectroscopic properties of several N-alkyl-N-nitrosoureas, N,N'-dialkyl-N-nitrosoureas, and N,N',N'-trialkyl-N-nitrosoureas have been studied in carbon disulfide and chloroform solutions.The NH stretching frequencies in the IR spectra have been observed in both concentrated and dilute solution and in the presence of added dioxane.The results indicate that there is a strong intramolecular hydrogen bond in the mono- and dialkylnitrosoureas.The chemical shifts and line widths of the NMR spectra have also been studied in these solvents.The large chemical shift differences, about 1.3 ppm, for the NH protons in the monoalkylnitrosoureas and other spectroscopic features in the monoalkyl- and dialkylnitrosoureas also indicate that an intramolecular hydrogen bond contributes to a strong conformational preference.The temperature dependence of the NMR spectra of several N,N',N'-trialkyl-N-nitrosoureas establishes that the energy barrier for rotation about the carbon dialkylamide bond is about 13 kcal mol-1.Dipolar resonance interactions are primarily responsible for this barrier.This interaction is augmented by a strong, 8-10 kcal mol-1, hydrogen bond in the mono- and dialkylnitrosoureas.
- Snyder, John K.,Stock, Leon M.
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p. 886 - 891
(2007/10/02)
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- Process for preparing alkyl isocyanates
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Alkylisocyanates are prepared by reacting a phenol or substituted phenol and phosgene in a halogenated hydrocarbon solvent with aqueous alkali metal hydroxide to produce a corresponding chloroformate, reacting the resulting chloroformate solution with aqueous alkylamine to give a corresponding N-alkylcarbamate which, after solvent is stripped, is then pyrolyzed to yield the alkyl isocyanate. Solvent and the starting phenol may be recovered and recycled to the process.
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- Method for preparing acylated products
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Acylation of nitrogen containing compounds utilizing esters as acylation agents in the presence of salts of substituted pyridine compounds.
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