- Preparation and reaction of uracil substituted cyclen and cyclam: formation of tricyclic guanidinium and dihydroimidazolium salts
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Di-uracil substituted cyclen derivatives were prepared by the reaction of cyclen with 6-chloro-1-methyluracil or 6-chloro-1,3-dimethyluracil. The reaction of cyclam with 6-chloro-1,3-dimethyluracil gave a similar di-uracil substituted cyclam. The 1,7-di-uracil substituted cyclen was converted to the tricyclic guanidinium salt and acylurea upon heating in DMSO in the presence of weak acid. The 1,8-di-uracil substituted cyclam gave a tricyclic dihydroimidazolium salt under the same conditions. These reactions can be explained by an intramolecular uracil ring-breaking reaction mechanism.
- Watanabe, Soichiro,Komori, Ayako,Saito, Masayuki,Uchida, Akira
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Read Online
- Reactions of 2-amino-2-thiazolines with isocyanates and isothiocyanates. Chemical and computational studies on the regioselectivity, adduct rearrangement, and mechanistic pathways
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2-Amino-2-thiazoline derivatives bearing alkyl or aryl substituents at exocyclic nitrogen have been condensed with different isocyanates and isothiocyanates. The addition occurs at ring endocyclic nitrogen in a regiospecific manner to afford kinetic and enthalpy-favored adducts. The unequivocal assignment of these structures has been confirmed by X-ray diffraction analyses of several compounds. The endo adducts do not rearrange on heating with the sole exception of adducts in which the exocyclic nitrogen remains unsubstituted. Trapping experiments in the presence of other isocyanates or isothiocyanates produce the formation of new endo adducts by acyl exchange in the reaction mixture. Semiempirical PM3 calculations full corroborate the higher stability of endo or exo adducts depending on the substitution pattern. The formation of adducts is compatible with a stepwise reaction mechanism, for which semiempirical transition structures could be located in the potential energy surface, and the global energetics of the process have been determined. The formation of the endo adducts proceeds with a smaller activation barrier.
- Avalos,Babiano,Cintas,Chavero,Higes,Jimenez,Palacios,Silvero
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Read Online
- On the Reaction of Acylium Salts with Isocyanates
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Alkyl isocyanates (3) react with acylium salts (2) in a 2:1 ratio to furnish 3,4-dihydro-2,4-dioxo-2H-1,3,5-oxadiazinium salts 4.These cyclic N-acyliminium salts are decomposed with catalytic amounts of water to give either oxadiazinium salts 5 or pyrimidinium salts 7.With aqueous base compounds 4 are transformed into acylureas 6.Hetero substituted open chain N-acyliminium slats (8a, 11c, 12c, 13f, 15g, 16a) are produced from 4 by treatment with heteronucleophiles such as methanol, p-anisidine, p-cresol, thiophenol, 1,3-dimethylurea, or benzohydrazide, respectively.Excess of nucleophile furnishes further degradation products of 4, e.g. oxonium salts (9a) and iminium salts (14f).
- Hamed, A.,Ismail, A.,Hitzler, M. G.,Jochims, J. C.
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Read Online
- Regioselective Formal [3+2] Cycloadditions of Urea Substrates with Activated and Unactivated Olefins for Intermolecular Olefin Aminooxygenation
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A new class of intermolecular olefin aminooxygenation reaction is described. This reaction utilizes the classic halonium intermediate as a regio- and stereochemical template to accomplish the selective oxyamination of both activated and unactivated alkenes. Notably, urea chemical feedstock can be directly introduced as the N and O source and a simple iodide salt can be utilized as the catalyst. This formal [3+2] cycloaddition process provides a highly modular entry to a range of useful heterocyclic products with excellent selectivity and functional-group tolerance.
- Wu, Fan,Alom, Nur-E,Ariyarathna, Jeewani P.,Na?, Johannes,Li, Wei
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supporting information
p. 11676 - 11680
(2019/07/31)
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- Cyclization Reaction of Donor-Acceptor Oxiranes with N,N′-Disubstituted Thioureas: A Domino Process to trans-Dihydropyrimidines
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An unprecedented cyclization reaction of donor-acceptor oxiranes with N,N′-disubstituted thioureas to construct trans-dihydropyrimidines is presented. Preliminary reaction mechanism studies demonstrated that the reaction underwent sequential cycloaddition/amine ester exchange/oxygen-sulfur exchange/desulfuration/Michael addition process. A wide range of trans-dihydropyrimidines were produced with high yields up to 94% by using this method.
- Wang, Jing,Zhang, Qi-Ying,Xie, Ming-Sheng,Wang, Dong-Chao,Qu, Gui-Rong,Guo, Hai-Ming
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supporting information
p. 6578 - 6582
(2018/10/20)
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- METHOD FOR ALKYLATING AN AMINO COMPOUND
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The invention relates to a method for alkylating an amino compound, characterized in that at least one triazine derivative of general formula (I) or at least one urea or urea derivative of the general formula (II), (II), wherein ? R4 and R5 mean independently from each other Q1 or a moiety of the formula R6-N-R7 or R8-N-R9 bound with its central nitrogen atom to the triazine ring of the structure of formula (I), whereat - Q1 means a linear or branched C1-C30-alkyl or a cyclic substituent in form of a C5-C20-cycloalkyl, a C5-C20-aryl, a C1-C20-alkylsubstituted C5-C20-aryl or an amide of a cyclic unsaturated carboxylic acid, whereat the C1-C30-alkyl or the cyclic substituent can be interrupted by one or multiple oxygen atoms, sulphur atoms, substituted nitrogen atoms and/or by one or multiple groups of the type –C(O)O-,-OC(O)-,-C(O)- and/or –OC(O)O-, ? R1, R2, R3, R6, R7, R8 and R9 mean independently from each other H, linear or branched C1-C20-alkyl, C5-C20-cyclo alkyl, C5-C20-aryl, C1-C20-alkylsubstituted C5-C20-aryl, which in each case can be interrupted by one or multiple oxygen atoms, sulphur atoms and/or substituted nitrogen atoms and/or by one or multiple groups of the type –C(O)O-, - OC(O)-, -C(O)- and/or –OC(O) O- and/or can be functionalized by one or multiple hydroxyl groups and/or mercapto groups, and ? X means O or S, is reacted with at least one alcohol of the general formula (III) R10-OH wherein R10 means a linear or branched C1-C20-alkyl, C5-C20-cycloalkyl, or C1-C20- alkylsubstituted C5-C20-aryl, which can be in each case interrupted by one or multiple oxygen atoms, sulphur atoms, substituted nitrogen atoms and/or by one or multiple groups of the type –C(O)O-, -OC(O)-, -C(O)- and/or –OC(O)O- and/or can be functionalized by one or multiple hydroxyl groups and/or mercapto groups, wherein the reaction is carried out in the presence of at least one Ruthenate of the general formula (IV) Mn(RuO4) and/or at least one Perruthenate of the general formula (V) M(RuO4)n wherein the cation M is selected from a group comprising an alkali, earth alkali or substituted or non-substituted ammonium cation.
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Page/Page column 14; 15
(2018/06/12)
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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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- 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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p. 9168 - 9176
(2018/06/08)
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- Direct Conversion of Haloarenes to Phenols under Mild, Transition-Metal-Free Conditions
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A high-yielding and practical method for the synthesis of phenols from electron-deficient haloarenes and heteroarenes has been developed. The products are formed from acetohydroxamic acid as the hydroxide source via a novel SNAr reaction/Lossen rearrangement sequence. Notably, these reactions employ inexpensive and air-stable reagents, require no special handling, occur under mildly basic conditions, and form products in high yields in the presence of electrophilic and protic functionality. The utility of this methodology is demonstrated by the high-yielding hydroxylation of two base-sensitive complex substrates.
- Fier, Patrick S.,Maloney, Kevin M.
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supporting information
p. 2244 - 2247
(2016/06/01)
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- Direct extraction of carbonyl from waste polycarbonate with amines under environmentally friendly conditions: Scope of waste polycarbonate as a carbonylating agent in organic synthesis
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An efficient green method for converting waste polycarbonate into urea derivatives by reacting with primary amines has been developed. Simple treatment of polycarbonate plastic with primary amines in a closed vial at 80 °C without using any catalyst and toxic solvents made this process environmentally friendly. Digestion of the waste polycarbonate obtained from CDs and DVDs with amines affords functionalized urea and 4,4′-(propane-2,2-diyl)diphenol (BPA, bisphenol-A). The procedure is optimized to get maximum conversion of polymer to urea and its derivatives as a major product. The purification procedure to isolate the urea derivatives in the presence of bisphenol-A has been tuned to avoid chromatographic procedures. This environmentally friendly method provides (i) an alternative for recycling BPA from polycarbonate, (ii) a method of obtaining useful product like urea derivatives, (iii) scope for new carbonylating agents in organic synthesis, (iv) an amine functionalized polycarbonate surface. This journal is
- Singh, Sukhdeep,Lei, Yong,Schober, Andreas
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p. 3454 - 3460
(2015/02/19)
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- Unexpected formation of 4-alkyl-5-(4-alkylthiosemicarbazido)-4,5-dihydro-1, 2,4-triazine-3(2H)-thiones from 1,3-dialkyl-4,5-bis-(4-alkylthiosemicarbazido) imidazolidin-2-ones in acidic medium
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4-Alkyl-5-(4-alkylthiosemicarbazido)-4,5-dihydro-1,2,4-triazine-3(2H) -thiones are obtained either by heating 1,3-dialkyl-4,5-bis-(4- alkylthiosemicarbazido)imidazolidin-2-ones in acidic medium or the reaction of 1,3-dialkyl-4,5-dihydroxyimidazolidin-2-on
- Gazieva, Galina A.,Poluboyarov, Pavel A.,Kolotyrkina, Natal'ya G.,Lubuzh, Elena D.,Kravchenko, Angelina N.
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- Oxidation of 1,3,7-trimethylxanthine by hypochlorite ion
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The kinetics of the oxidative conversion of 1,3,7-trimethylxanthine upon treatment with hypochlorite ions (OCl-) in aqueous medium at 283-298 K and pH 8.2 was studied. The reaction order with respect to each component was determined and proved to be 1. It was established that the temperature dependence of the reaction rate follows the Arrhenius equation. The activation parameters of the reaction were measured: E a = 33.58 kJ/mol, ΔH ≠ = 31.12 kJ/mol, ΔS ≠ = -170.02 J/(K mol), ΔG ≠ = 81.45 kJ/mol. The stoichiometry of the reaction was studied, and the chemistry of the oxidative conversion of caffeine treated with OCl- is discussed.
- Kheidorov,Ershov,Chalyi,Titorovich
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experimental part
p. 1358 - 1362
(2011/10/05)
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- Specific features of the reaction of vanadyl acetylacetonate with tert-butyl hydroperoxide
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It was found for the first time that the reaction of N-(carboxyalkyl)ureas (ureido acids) with 4,5-dihydroxy-1,3-dimethyl-4,5-diphenylimidazolidin-2-one in methyl or isopropyl alcohol proceeds through the tandem sequence of α-ureidoalkylation and esterification to form the earlier unknown N-(carboxyalkyl)glycoluril methyl or isopropyl esters. N-(Carboxyalkyl)- glycolurils of a new-type substitution were obtained by alkaline hydrolysis of their isopropyl esters, the structure of one of them was confirmed by X-ray diffraction analysis.
- Stepovik, L. P.,Gulenova, M. V.
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scheme or table
p. 1427 - 1432
(2011/06/27)
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- PROCESS FOR STRAIGHTENING KERATIN FIBRES WITH A HEATING MEANS AND DENATURING AGENTS
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The invention relates to a process for straightening keratin fibres, comprising: (i) a step in which a straightening composition containing at least two denaturing agents is applied to the keratin fibres, (ii) a step in which the temperature of the keratin fibres is raised, using a heating means, to a temperature of between 110 and 250° C.
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- Preparation of mono-, di-, and trisubstituted ureas by carbonylation of aliphatic amines with S,S-dimethyl dithiocarbonate
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General procedures are reported to prepare N-alkylureas, N,N′-dialkylureas (both symmetrical and unsymmetrical), and N,N,N′-trialkylureas by carbonylation of aliphatic amines, employing S,S-dimethyl dithiocarbonate (DMDTC) as a phosgene substitute. All reactions were carried out in water. Symmetrical disubstituted ureas were prepared directly working at 60°C with a molar ratio of DMDTC:amine = 1:2, preferably under nitrogen. Unsymmetrical ureas were prepared in two steps via S-methyl N-alkyl-thiocarbamate intermediates, which are formed selectively in the first step at room temperature. These intermediates react in the second step with ammonia or various aliphatic amines, both primary and secondary, at temperatures varying between 50 and 70°C. All the target ureas were obtained in high yields (28 examples, average yield 94%) and with very high purity (generally >99.2%). Also to be noted is the recovery of a co-product of industrial interest, methanethiol, in an amount of two moles for each mole of DMDTC, with complete exploitation of the reagent. Georg Thieme Verlag Stuttgart.
- Artuso, Emma,Degani, Iacopo,Fochi, Rita,Magistris, Claudio
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p. 3497 - 3506
(2008/09/19)
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- Kinetics and mechanism of the Co(II)-assisted oxidation of thioureas by dioxygen
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Catalytic oxidation of N,N′-dimethylthiourea and thiourea by dioxygen in water using a new cobalt(II) complex of octasulfophenyltetrapyrazinoporphyrazine was performed under mild conditions. The reaction is shown to include the formation of an intermediate anionic five-coordinate complex followed by an unusual two-electron oxidation to produce the corresponding urea and elemental sulfur (S8). Kinetic and thermodynamic parameters for the different reaction steps of the process were determined. Drastic differences in catalytic activity of cobalt and iron octasulfophenyltetrapyrazinoporphyrazines were observed. The Royal Society of Chemistry 2005.
- Kudrik, Evgeny V.,Theodoridis, Alexander,Van Eldik, Rudi,Makarov, Sergei V.
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p. 1117 - 1122
(2007/10/03)
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- Expanded Chemistry of Formamidine Ureas
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(Equation presented) 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.
- Diaz, David D.,Finn
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- Quantitative solid-state reactions of amines with carbonyl compounds and isothiocyanates
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A series of solid-state reactions is reported of gaseous or solid amines with aldehydes to give imines, with solid anhydrides to give diamides (therefrom imides) or amidic carboxylic salts or imides, with solid imides to give diamides, with solid lactones or carbonates to give functionalized carbamic esters, with polycarbonates to give degradative aminolysis, and with solid isothiocyanates to give thioureas. Diamides give imides by solid-state thermolysis or acid catalysis. Various double, two-step, 3-cascade, and sequential reactions are reported in the solid state without melting. The yields are quantitative in 53 reported reaction examples and no workup (except for washings in four cases) is required in the 100% yield reactions. Three initially solid-state reactions but with liquid product were not quantitative. An upscaling to the kg scale shows promise of the technique for large scale applications. Supermicroscopic analyses with AFM elucidate the solid-state mechanism by virtue of far-reaching anisotropic molecular movements in three-step processes. Gas-solid aminolyses of polycarbonates are also studied with AFM. The implications to sustainable chemistry are discussed. (C) 2000 Elsevier Science Ltd.
- Kaupp, Gerd,Schmeyers, Jens,Boy, Juergen
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p. 6899 - 6911
(2007/10/03)
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- Liquid-phase process for preparing mono- and dimethylurea
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Kinetics of homogeneous liquid-phase reaction of urea with monomethylamine was studied by differentiation of the time dependence of the concentrations of the reaction products. Based on the results obtained, a unit for continuous synthesis of mono- and dimethylurea was developed.
- Bazanov,Berdichevskii,Bogorad,Datsevich,Mukhortov,Sokolova
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p. 2040 - 2042
(2007/10/03)
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- MECHANISM OF URAPIDIL DEGRADATION IN AQUEOUS SOLUTION
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During the hydrogen ion-catalyzed hydrolysis of urapidil degradation at the bond C6-NH takes place and the formation of 1,3-dimethylbarbituric acid (DMB) and 3-propylamin (PPA).The hydroxide ion-catalyzed hydrolysis of urapidil is sequent of pseudofirst-order reaction N- amid of the malonic acid (PP) is the medial product which is formed the degradation of the bond N1-C6 and N3-C4 in the ring of uracil.In the hydroxide ion-catalyzed reaction, the compound PP splits the malonic acid and 3-propylamin (PPA') is formed.DMB, PPA, PPA' and PP compounds were isolated and its chemical structure were confirmed by spectroscopic methods. - Keywords: Urapidil; stability; mechanism of degradation
- Zajac, Marianna,Muszalska, Izabela
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p. 407 - 414
(2007/10/03)
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- Heterocyclic transformations. Part 7. Unprecedented transformations of 1,3-dialkyl-5-formyluracils to 1,3-dialkyl-7-hydroxyquinazolines
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1,3-Dialkyl-5-formyluracil reacts with ethyl acetoacetate, acetylacetone, benzoylacetone, acetoacetamide and acetoacetanilide under phase transfer catalytic conditions to provide exclusively the annulation products: 6-substituted-1,3-dialkyl-7-hydroxyquinazolines or/and also 4-hydroxybenzamide derivatives.Similar reaction with cyanoacetamide provides 6-cyano-7-hydroxy-1,3-dimethylpyridopyrimidine.The reaction mechanism prevailing in these reactions has been rationalized.
- Singh, Harjit,Singh, Palwinder,Chimni, Swapandeep Singh,Kumar, Subodh
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p. 2363 - 2368
(2007/10/02)
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- Novel Triazenes and Triazolines from the Base-Catalyzed Hydrolysis of 1,3-Dialkyl-3-acyltriazenes
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The products and mechanism of hydrolytic decomposition of a series of 1,3-dialkyl-3-acyltriazenes were studied in alkaline buffers.In general the mechanism of decomposition involves deacylation leading to the formation of the parent 1,3-dialkyltriazene.The solvent deuterium isotope effect (kH2O/kD2O) is less than 1.0, indicating specific base catalysis.A plausible mechanistic explanation is rapid reversible attack by hydroxide ion, followed by rate-limiting heterolysis of the N(1)-acyl bond.The resultant, 1,3-dialkyltriazene is somewhat unstable under the reaction conditions and undergoes subsequent hydrolysis, a reaction previously shown to be specific acid-catalyzed.When the N(1) alkyl group is 2-chloroethyl, unusual products are obtained.For the 3-acetyl and 3-carbethoxy derivatives, the initial deacylation product, 1-(2-chloroethyl)-3-methyltriazene, efficiently cyclizes to form 1-methyltriazoline.The 3-(methylcarbamoyl) derivative does not deacylate, but instead undergoes dehydrohalogenation to 1-vinyl-3-methyl-3-(methylcarbamoyl)triazene.
- Smith, Richard H.,Wladkowski, Brian D.,Herling, Julie A.,Pfaltzgraff, Timothy D.,Taylor, Jesse E.,et al.
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p. 6448 - 6454
(2007/10/02)
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- 1,3-Dialkyl-3-acyltriazenes: Products and Rates of Decomposition in Acidic and Neutral Solutions
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The products and mechanism of hydrolytic decomposition of a series of 1,,3-dialkyl-3-acyltriazenes were studied in both acidic and neutral buffers.In the acidic region, the products are alkyl alcohols derived from the N(1) alkyl group and amides derived from the intact N(3) portion of the molecule.The solvent deuterium isotope effect (kH2O/kD2O)) is less than 1.0.The mechanism is specific acid catalyzed, involving rapid reversible protonation of the 3-acyl group followed by scision of the N(2)-N(3) bond to generate an amide and an alkyl diazonium ion.The (2-hydroxyethyl)diazonium ion gives ethylene glycol and acetaldehyde, while the (2-chloroethyl)diazonium ion yields 2-chloroethanol.In the neutral region, the products are similar to those found in acidic buffers, alkyl alcohols, and amides.At this pH the (2-chloroethyl)diazonium ion produces ethylene glycol and acetaldehyde in addition to 2-chloroethanol.The solvent deuterium isotope effect (kH2O/kD2O) is greater than 1.0.The mechanism involves unimolecular heterolylsis of the N(2)-N(3) bond to form an amide anion and an alkyldiazonium ion.The methyldiazonium ion leads to incorporation of deuterium in the methyl group of the products, indicating the existence of an equilibrium between the metastable methyldiazonium ion and diazomethane.
- Smith, Richard H.,Wladkowski, Brian D.,Herling, Julie A.,Pfalzgraff, Timothy D.,Pruski, Brunon,et al.
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p. 654 - 661
(2007/10/02)
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- Mechanistic Studies in the Chemistry of Thiourea. Part 2. Reaction with Benzil in Acid Solution
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Benzil reacts with 1,3-dimethylthiourea, 1-methylthiourea, and thiourea in acid solution to give 4,5-diphenyl-4-imidazolines (3) which, in the cases of 1-methylthiourea and thiourea, readily form disulphides 11.Another product of reaction is a bicyclic compound 4 in which it appears that in one thiourea moiety sulphur has been replaced by oxygen.A mechanistic pathway for the formation of 3 and 4 is proposed involving thioureas acting as sulphur nucleophile, urea as a leaving group, and the thermal decomposition of thiiranes.
- Broan, Christopher J.,Butler, Anthony R.
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p. 1501 - 1504
(2007/10/02)
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- Amino protection using triazones
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Primary amines protected by incorporation into a "triazone" derivative (3) are stable to various reduction, oxidation, organometallic, and basic hydrolysis conditions, and may be regenerated by treatment with aqueous ammonium chloride at 70°. An application to polyamine synthesis is described.
- Knapp, Spencer,Hale, Jeffrey J.,Bastos, Margarita,Gibson, Frank S.
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p. 2109 - 2112
(2007/10/02)
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- Activation volumes for aquation of chromium(III) pentaammine complexes with neutral leaving groups: Comparison with and mechanistic differentiation from cobalt(III) analogues
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The pressure dependence of the spontaneous aquation of a series of Cr(NH3)5L3+ complexes with L = formamide, dimethylformamide, urea, N,N′-dimethylurea, dimethyl sulfoxide, trimethyl phosphate, and N,N′-dimethylacetamide has been determined. The temperature dependence of aquation of the series has also been determined. The activation volume (ΔV?) lies in the limited range -3.2 to -8.7 cm3 mol-1 and is not related clearly to leaving group size. An approximate correlation between ΔV? and activation entropy (ΔS?) exists. The average ΔV? of ～-6 cm3 mol-1 is an estimate of the solvent-independent intrinsic component of ΔV? for reaction of a chromium(III) complex and is interpreted as being indicative of an associative interchange (Ia) mechanism, contrasting with an average ΔV? of ～+2 cm3 mol-1 in the analogous cobalt(III) series where a dissociative interchange (Id) mechanism apparently applies. Apparent molar volumes of the series of complexes were determined. The "volume profile" approach applied earlier to the cobalt(III) series yields in the case of the chromium(III) series a different result that supports a mechanistic differentiation between chromium(III) and cobalt(III).
- Curtis, Neville J.,Lawrance, Geoffrey A.,Van Eldik, Rudi
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p. 329 - 333
(2008/10/08)
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- Covalent Adduct Formation in 1,2,4-Thiadiazolo Activated Pyrimidinones
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Preparation of 1-(1,2,4-thiadiazol-5-yl)-2(1H)-pyrimidinones is described.The polarization from the thiadiazole ring enhances the ?-electron deficiency of the pyrimidine ring.The latter forms covalently bound adducts with hydroxylic solvent molecules in a regiospecific manner.The adducts are stable, isolable molecules, but on heating in a hydroxylic solvent exchange of the solvent molecule in the adduct may take place.
- Keilen, Gunnar,Undheim, Kjell
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p. 362 - 366
(2007/10/02)
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- Studies of Reactions of 1,3,5-Trimethylbiuret and 1,3-Dimethylurea with Chloroform
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1,3,5-Trimethylbiuret and 1,3-dimethylurea react with chloroform at temperatures above 200 deg C to produce 1,3,5-trimethyl-1,3,5-triazinane-2,4-dione (4), 1,3-dimethyl-1,3,5-triazinane-2,4,6-trione (5), and 1,3,5-trimethyl-1,3,5-triazinane-2,4,6-trione (3), besides minor quantities of other by-products, via trimerization reactions involving MIC, isocyanic acid, and N-methylenemethylamine.
- D'Silva, Themistocles D. J.,Lopes, Anibal
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p. 795 - 796
(2007/10/02)
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- Studies of Methyl Isocyanate Chemistry in the Bhopal Incident
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Following the methyl isocyanate leak from Tank 610 at the Bhopal plant, the residual material from the tank was analyzed for its contents.Approximately 70percent of the residue was comprised of three cyclic materials: 1,3,5-trimethyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione or methyl isocyanate trimer (5), 1,3-dimethyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione or dimethyl isocyanurate (6), and dihydro-1,3,5-trimethyl-1,3,5-triazine-2,4-(1H,3H)-dione or dihydrotrimethyltriazinedione (7).Minor quantities of methyl-substituted ureas, biurets, and amine hydrochlorides were also found.The composition of the residue was replicated very closely by the products obtained when a mixture of methyl isocyanate (84.4percent), chloroform (12.0percent), and water (3.6percent) was heated at 225 deg C under pressure in a stainless steel reactor.Experimental results are consistent with the view that under these conditions methyl isocyanate reacts initially with water to form 1,3-dimethylurea (1) and 1,3,5-trimethylbiuret (2).At temperatures between 100 deg C and 225 deg C these products decompose to reactive intermediates which further react exothermically to form the aforementioned cyclic materials, trimethylurea, and mono-, di-, and trimethylamine hydrochlorides.The decomposition of 1 and 2 is facilitated by the presence of chloroform and metals.Other experiments involving 13C-enriched chloroform have given support to the proposed mechanisms for formation of 6 and 7.
- D'Silva, Themistocles D. J.,Lopes, Anibal,Jones, Russell L.,Singhawangcha, Sureerat,Chan, John K.
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p. 3781 - 3788
(2007/10/02)
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- The Kinetics of Hydrolysis of Methyl and Phenyl Isocyanates
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The hydrolysis of phenyl isocyanate is subject to general base catalysis by tertiary amines and the point for water falls on the Bronsted plot, which indicates that the uncatalysed reaction involves two molecules of water, one acting as a nucleophile and the other as a general base.The rather small solvent isotope effect, kw H2O/kw D2O = 1.65, and the proton inventory, are discussed.The hydrolysis of methyl isocyanate (unlike phenyl isocyanate) is acid-catalysed, probably proceeding with pre-equilibrium protonation.Methyl isocyanate reacts with hydrogenphosphate dianion and with hydrogensulphate ion, forming mixed anhydride species.The formal reaction with hydrogensulphate ion may proceed by pre-equilibrium protonation followed by nucleophilic attack by sulphate ion.
- Castro, Enrique A.,Moodie, Roy B.,Sansom, Peter J.
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p. 737 - 742
(2007/10/02)
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- N-Methylcarbamoyl Phosphates, II. Thermal Decomposition
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The thermal decomposition of various salts of mono-N-methylcarbamoyl and bis-N-methylcarbamoyl phosphoric acid in aprotic and protic solvents (acetonitrile, trichloromethane, alcohols) and in the solid state has been studied in detail.Final products are mono-, di-, poly-, and cyclophosphates, in addition phosphoric acid esters if alcohols are used as solvents; and either sym. dimethylurea or methyl isocyanate and methylamine.The spontaneous decomposition of sparingly soluble N-methyl carbamoyl phosphates in aqueous suspensions to yield slightly soluble diphosphates demonstrates clearly that the reaction of calcium hydrogen phosphate with alkali cyanates via calcium carbamoylphosphate to give calcium diphosphate - which has been considered a prebiotic key reaction - is not a result of a special feature of the structure of the intermediate product. - Keywords: N-Methylcarbamoyl Phosphates, Decomposition
- Seel, Fritz,Klein, Norbert
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p. 1095 - 1099
(2007/10/02)
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- The Dehydration of Ureas by Two-Phase Dichlorocarbene Reaction, a Synthetic Access to Substituted Cyanamides
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A wide variety of N,N-disubstituted ureas are dehydrated in the CHCl3/NaOH catalytic two-phase system under mild conditions.The sequence of urea-transamidation and dehydration thus offers a profitable approach to aprotic cyanamides.Among various tested PT-catalysts tertiary amines prove to be the most efficient and favourable ones.Tertiary amines may also be used advantageously in the transformation of carboxylic amides and thioamides to the corresponding nitriles.The application of the same technique is less suitable in the case of N-mono-substituted ureas, N,N'-disubstituted ureas as well as N(dialkylaminomethylidene)ureas, because consequent reactions of the primarily formed cyanamides predominate.Problems concerning the dehydration mechanism are elucidated in terms of HMO-perturbation theory.
- Schroth, W.,Kluge, H.,Frach, R.,Hodek, W.,Schaedler, H. D.
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p. 787 - 802
(2007/10/02)
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- Synthesis of Novel N-Nitrosothioureas and Examination of Their Mechanisms of Formation by High-Field Nitrogen-15 and Carbon-13 Nuclear Magnetic Resonance Spectra of Specifically Labeled Compounds
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An examination by 15N NMR of Na15NO2 under various conditions of acidity led to the identification of several electrophilic nitrogen species.This permitted the selection of reaction conditions of low acidity which favor nitrosation at the nitrogen atom of thioureas rather than on the normally more reactive sulfur, leading to the isolation of novel N-nitrosothioureas.In contrast it was shown by employing 15N and 13C labeling that higher acidity conditions favor reaction via a detectable thionitrosyl intermediate.
- Lown, J. William,Chauhan, Shive M. S.
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p. 507 - 512
(2007/10/02)
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- Convenient Methods for Syntheses of Active Carbamates, Ureas and Nitrosoureas Using N,N'-disuccinimido Carbonate (DSC)
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The reaction of DSC and amino compounds afforded the corresponding carbamates which were able to be converted into ureas and nitrosoureas.
- Takeda, Kazuyoshi,Akagi, Yoshie,Saiki, Atsuko,Tsukahara, Toshiko,Ogura, Haruo
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p. 4569 - 4572
(2007/10/02)
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- Pyrimidine Derivatives and Related Compounds. Part 45. Synthesis of 4-Allophanoylpyrazoles via a Pyrimidine-to-pyrazole Ring Transformation
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Reaction of the 5-formyluracil derivatives (1a-f) with hydrazines in the presence of acetic acid produced a ring contraction to give the corresponding 4-allophanoylpyrazoles (2a-h).Further treatment of these pyrazoles (2a-h) with sodium methoxide afforded methyl pyrazole-4-carboxylate (3a).Conceivable mechanisms for the present pyrimidine-to-pyrazole transformation were discussed.
- Hirota, Kosaku,Kitade, Yukio,Shimada, Kaoru,Senda, Shiego,Maki, Yoshifumi
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p. 1293 - 1298
(2007/10/02)
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- PERCARBAMATE DE t-BUTYLE ET SES DERIVES N-ALKYLES, N,N-DIALKYLES ET N-AZACYCLANIQUES: PREPARATION ET THERMOLYSE EN SOLUTION
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Several tert-butyl percarbamates have been prepared by the reaction of amines with tert-butyl imidazoylpercarboxylate.The thermal decomposition of these peresters in solution led to the characteristic products of homolytic processes.The kinetic study of the thermolysis has been performed by Differential Scanning Microcalorimetry.It showed the influence of the nitrogen atom substitution on the percarbamate stability.The kinetic study of the decompositions of percarbamates derived from cyclic amines showed an important effect of the cycle size on the rate constant.Very different transition state levels are responsible for this phenomenon.A stereoelectronic origin-from the overlapping of the p-orbital of the nitrogen atom and the ? bond of the carboxyl- has been advanced to account for this result.
- Buorgeois, M. J.,Campagnole, M.,Filliatre, C.,Maillard, B.,Manigand, C.,et al.
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p. 3569 - 3577
(2007/10/02)
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- Synthesis of Nitrosothioureas. 15N N.M.R. Evidence for the Formation of Thionitrosyl Compounds in the Nitrosation of Thioureas
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Nitrosothioureas may be prepared by treatment of thioureas with NaNO2 in 0.1 N HCl at -5 deg C by direct N-nitrosation whereas 15N n.m.r. studies at -10 deg C which employed specifically 15N-enriched compounds revealed the intermediacy of a thionitrosyl compound under more acidic conditions which gave the urea by hydrolysis.
- Lown, J. William,Chauhan, Shive M. S.
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p. 675 - 676
(2007/10/02)
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- Fluorodiazadiphosphetidines, XI: A New Method of Preparation for the Betain-like Compound (CH3N)6P4F8
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A new synthetic route for the preparation of the betain-like compound (CH3N)6P4F8 from (CH3NPF3)2, N-methyl-hexamethyldisilazane and N,N'-dimethyl-urea has been found.The steps of this multi-stage reaction could be rationalized to a far extent. - Keywords: Aza; Cyclic (non-carbon); Heterocyclic (N, P); Phospa; Silylated N,N'-dimethyl-urea
- Kubjacek, Manfred,Utvary, Kurt
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p. 1353 - 1358
(2007/10/02)
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- Pyrimidine Derivatives and Related Compounds. 39. A Novel Cycloaromatization Reaction of 5-Formyl-1,3-dimethyluracil with Three-Carbon Nucleophiles. Synthesis of Substituted 4-Hydroxybenzoates
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Treatment of 5-formyl-1,3-dimethyluracil (1) with α-substituted acetone derivatives (C-C-C type nucleophiles) such as acetylacetone, acetoacetamide, ethyl acetoacetate, and phenylacetone in basic media affords the corresponding 4-hydroxybenzoates (4).On the other hand, treatment of 1 with cyanoacetamide, a C-C-N type nucleophile, gives the nicotinate 8.A mechanism for this cycloaromatization was proposed on the basis of reaction of 5-formyl-1,3-dimethyluracil-d1 (6) with acetylacetone.
- Hirota, Kosaku,Kitade, Yukio,Senda, Shigeo
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p. 3949 - 3953
(2007/10/02)
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- Synthesis and Photolysis of 1,4-Dialkyl-1,4-dihydro-5H-tetrazol-5-ones and -thiones. A Novel Approach to Diaziridinones and Carbodiimides
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The regioselective alkylation of the 1-tert-butyl-1,4-dihydro-5H-tetrazol-5-one (7) produced the 1,4-dialkyltetrazolones 8b and c.The electron impact induced decomposition of the known, most simple tetrazolone 8a proceeded via a cycloelimination into methyl azide and methyl isocyanate.On photolysis in acetonitrile or pentane, the tetrazolones 8 lost nitrogen and formed 1,2-dialkyldiaziridinones 24, of which 24c was isolated in pure form.Very reactive alkylating reagents, e.g. methyl fluorosulfonate, trimethyloxonium tetrafluoroborate, or tert-butyl alcohol/tetrafluoroboric acid in ether, preferentially alkylated N-3 of 1-methyl-5-(methylthio)-1H-tetrazole (9a); dimethyl sulfate reacted almost equally at N-3 or N-4.In the mixture of the salts 10a and 11a obtained in this way, only 11a was demethylated at the sulfur atom by triethylamine in acetonitrile affording the easily separable tetrazolethione 5a.Diazomethane methylated 1-tert-butyl-1,4-dihydro-5H-tetrazole-5-thione (18b) predominantly at the sulfur atom.In contrast, 2-diazopropane gave approximately equal fractions of S-alkylation and N-4-alkylation producing the tetrazolethione 5c.Besides fragment ions resulting from cycloelimination products, in the electron impact induced decomposition of the most simple tetrazolethione 5a, ions were observed which correspond to loss of nitrogen from the molecular ion.On photolysis in alkanes or acetonitrile in the temperature range between +20 and -40 deg C the tetrazolethiones lost nitrogen furnishing high yields of sulfur and the carbodiimides 30.
- Quast, Helmut,Bieber, Lothar
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p. 3253 - 3272
(2007/10/02)
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- A NOVEL SYNTHESIS OF PYRIDOPYRIMIDINES BY REACTION OF URACILS WITH 6-AMINOURACILS VIA PYRIMIDINE-TO-PYRIDINE TRANSFORMATION.
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Reaction of 1,3-dimethyluracils with 1,3-dialkyl-6-aminouracils in basic media caused the pyrimidine-to-pyridine transformation to afford new pyridopyrimidine derivatives.A plausible mechanism for the ring transformation is offered.
- Hirota, Kosaku,Kitade, Yukio,Senda, Shigeo
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p. 407 - 410
(2007/10/02)
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- A Novel Ring Transformation of Uracil into the Benzene Ring System
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Reaction of 5-formyl-1,3-dimethyluracil with some active methylene compounds in the presence of base causes novel ring transformations to give the p-hydroxybenzoates and the nicotinate.
- Hirota, Kosaku,Kitade, Yukio,Senda, Shigeo
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p. 413 - 414
(2007/10/02)
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- Activation of N-Hydroxy Compounds by P-O Bond Formation through Anodic Oxidation of Triphenylphosphine
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Controlled potential electrolyses of triphenylphosphine (TPP) in acetonitrile containing an excess of N-hydroxy compounds such as ketoximes, aldoximes, and hydroxamic acids were examined: subsequent treatment of the products under mild conditions gave amides, nitriles, and ureas, respectively.Electrolyses under conditions where the amounts of TPP were equal to or larger than those of the N-hydroxy compounds did not give satisfactory results.
- Ohmori, Hidenobu,Nakai, Shiro,Masui, Masaichiro
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p. 2247 - 2250
(2007/10/02)
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- Process for the production of amines
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Amines and substituted ureas are produced by reaction of carboxamides with hypochlorites in the presence of bromine, iodine, polymerization inhibitors, and/or haloamides and excess alkali metal hydroxide with or without the addition of primary or secondary amines. The products are perfumes and starting materials for the production of dyes, plant protection agents and perfumes.
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