- The mechanisms of hydrolysis of alkyl N-alkylthioncarbamate esters at 100°C
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The hydrolysis of ethyl N-ethylthioncarbamate (ETE) at 100°C was studied in the range of 7 mol/L HCl to 4 mol/L NaOH. The pH-rate profile showed that the hydrolysis occurred through specific acid catalysis at pH 6.5. The Hammett acidity plot and the excess acidity plot against X were linear. The Bunnett-Olsen plot gave a negative slope indicating that the conjugate acid was less hydrated than the neutral substrate. It was concluded that the acid hydrolysis occurred by an Al mechanism. The neutral species hydrolyzed with general base catalysis shown by the Bronsted plot with β = 0.48 ± 0.04. Water acted as a general base catalyst with (pseudo-)first-order rate constant, kN = 3.06 × 10-7 s-1. At pH > 6.5 the rate constants increased, reaching a plateau at high basicity. The basic hydrolysis rate constant of ethyl N,N-diethylthioncarbamate, which must react by a BAc2 mechanism, increased linearly at 1-3 mol/L NaOH with a second-order rate constant, k2 = 2.3 × 10-4 (mol/L)-1 s-1, which was 10 times slower than that expected for ETE. Experiments of ETE in 0.6 mol/L NaOH with an excess of ethylamine led to the formation of diethyl thiourea, presenting strong evidence that the basic hydrolysis occurred by the E1cb mechanism. In the rate-determining step, the E1cb mechanism involved the elimination of ethoxide ion from the thioncarbamate anion, producing an isothiocyanate intermediate that decomposed rapidly to form ethylamine, ethanol, and COS.
- Humeres, Eduardo,Sanchez, Maria De Nazare,Lobato, Conceicao M. L.,Debacher, Nito A.,De Souza, Eduardo P.
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- Green process development for the synthesis of aliphatic symmetrical N,N'-disubstituted thiourea derivatives in aqueous medium
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A highly efficient green process for the synthesis of N,N'-disubstituted aliphatic thiourea derivatives using primary aliphatic amines and carbon disulfide in aqueous medium at room temperature via a nonisothiocyanate route is described. This protocol illustrates the rapid preparation of N,N'-disubstituted aliphatic thiourea derivatives in excellent yields with some advantages such as no catalyst and simple workup without any side product formation. Moreover the new route is concise, chromatography-free, and adaptable to pilot-scale preparation.
- Jangale, Asha D.,Kumavat, Priyanka P.,Wagh, Yogesh B.,Tayade, Yogesh A.,Mahulikar, Pramod P.,Dalal, Dipak S.
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supporting information
p. 236 - 244
(2015/10/29)
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- Green Process Development for the Synthesis of Aliphatic Symmetrical N,N ′-Disubstituted Thiourea Derivatives in Aqueous Medium
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A highly efficient green process for the synthesis of N,N′-disubstituted aliphatic thiourea derivatives using primary aliphatic amines and carbon disulfide in an aqueous medium at room temperature via a nonisothiocyanate route is described. This protocol illustrates the rapid preparation of N,N′-disubstituted aliphatic thiourea derivatives in excellent yields with some advantages such as no catalyst and simple workup without any side product formation. Moreover, the new route is concise, does not require chromatography, and is adaptable to pilot-scale preparation. GRAPHICAL ABSTRACT.
- Jangale, Asha D.,Kumavat, Priyanka P.,Wagh, Yogesh B.,Tayade, Yogesh A.,Mahulikar, Pramod P.,Dalal, Dipak S.
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supporting information
p. 376 - 385
(2015/10/29)
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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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- α-Thioureidoalkylation of functionally substituted ureas: I. Tandem cyclization and esterification in reactions of N-(carboxyalkyl)ureas with 1,3-dialkyl-4,5-dihydroxy-4,5-diphenylimidazolidine-2-thiones in alcohols
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Acid-catalyzed reactions of N-(carboxyalkyl)ureas with 1,3-dialkyl-4,5- dihydroxy-4,5-diphenylimidazolidine- 2-thiones in methanol or propan-2-ol led to the formation of previously unknown ω-(4,6-dialkyl- 2-oxo-3a,6a-diphenyl- 5-thioxooctahydroimidazo[4,5-d]imidazol-1-yl)alkanoic acids and their methyl and isopropyl esters. The structure of some esters was proved by X-ray analysis. Methyl (4,6-diethyl-2-oxo-3a,6adiphenyl- 5-thioxooctahydroimidazo[4,5-d] imidazol-1-yl)acetate showed anxiolytic effect. Pleiades Publishing, Ltd., 2011.
- Baranov,Gazieva,Nelyubina,Kravchenko,Makhova
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experimental part
p. 1564 - 1571
(2012/03/10)
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- A convenient one-pot three component approach to synthesis of highly substituted iminothiazolines
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An efficient one-pot three component method was developed for the synthesis of highly substituted 2-iminothizolines by the reaction of isothiocyanates, primary amines and α-bromoketones in ambient temperature. The reaction produced the desired products in a completely regioselective manner in excellent yields (78-94%). The Japan Institute of Heterocyclic Chemistry.
- Samimi, Heshmat Allah,Mamaghani, Manouchehr,Tabatabaeian, Khalil
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experimental part
p. 2825 - 2833
(2011/04/17)
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- Synthesis of O-arylxanthates esters and derivatives
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No successful attempts have been made to synthesize O-arylxanthate esters from metal salts with alkylating agents because the metal derivatives are too unstable for the effective synthesis of the esters. In this work, substituted R-phenylxanthates (R = H, p-MeO, o-Me, p-F) were obtained as barium salts that upon reaction with alkyl halides produced O-arylxanthate esters. The ethylaminolysis of methyl O-phenylxanthate formed diethyl thiourea as the final product because of the similar nucleofugality of phenoxy and ethylthioxy moieties. A new method was used to obtain N-ethyl O-p-methoxyphenyl- thioncarbamate from the reaction of p-methoxyphenol and N-ethylisothiocyanate in a heterogeneous mixture of dichloromethane and aqueous phosphate buffer, pH 7.
- Humeres,Debacher,De Souza
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p. 1071 - 1079
(2008/09/18)
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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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- An environmentally benign method for the synthesis of symmetrical N,N′-disubstituted thioureas in a water medium
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An environmentally benign method for the synthesis of symmetrical N,N′-disubstituted thioureas in a water medium using poly(ethylene glycol)-400 (PEG-400) as a catalyst and a microwave as a heating source is described. Diaryl- and dialkyl-thioureas efficiently are synthesized by the reactions of thiourea with a variety of amines. This protocol has advantages of (a) no use of hazardous reagents and volatile organic solvents, (b) a rapid reaction rate, (c) a high yield, and (d) a simple work-up procedure. Copyright Taylor & Francis Inc.
- Li, Zheng,Wang, Zhi-Yuan,Zhao, Yan-Long,Xing, Yu-Lin,Zhu, Wei
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p. 2745 - 2750
(2007/10/03)
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- A Practical Amine-Free Synthesis of Symmetric Ureas and Thioureas by Self-Condensation of Iso(thio)cyanates
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Isocyanates and isothiocyanates are readily transformed into the corresponding symmetric N,N'-disubstituted ureas and thioureas upon treatment with pyridine-water with no formation of side products. Evidence is shown for an amine-free mechanistic pathway, probably involving (thio)carbamic anhydrides as reaction intermediates. The methodology is compatible with in situ generation of the isocyanate precursor from an acyl azide via Curtius rearrangement and with the presence of ester and amide functional groups in the molecule. Examples given include alkyl, aryl and carbohydrate substrates. This procedure allows the high yielding preparation of (thio)ureas in those cases where the related amine is not accessible.
- Blanco, Jose L. Jimenez,Barria, Claudio Saitz,Benito, Juan M.,Mellet, Carmen Ortiz,Fuentes, Jose,Santoyo-Gonzales, Francisco,Fernandez, Jose M. Garcia
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p. 1907 - 1914
(2007/10/03)
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- AZA SPIRO COMPOUNDS ACTING ON THE CHOLINERGIC SYSTEM WITH MUSCARINIC AGONIST ACTIVITY
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Compounds useful for treating diseases of the central or peripheral nervous system in mammals have formulae I-XII STR1 wherein ring A or A' together with the spiro-carbon atom constitutes a bridged or unbridged ring containing one or two ring nitrogen atoms; and the other symbols have specified values, subject to certain conditions.
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- Pesticidal compositions containing phosphoric esters and divalent sulphur compounds
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Pesticidal composition comprising: a pesticidal, phosphoric ester the molecule of which has at least one alkyl group of 1 to 3 carbon atoms, 0.05 to 10% of an agent stabilizing the said ester against decomposition by protonisation, together with adjuvants characterized in that the stabilizing agent comprises at least one sulphur compound containing per molecule at least one divalent sulphur atom of which one valence is bonded to an atom chosen from sulphur, carbon, nitrogen, hydrogen, and metals capable of giving a salt, the other valence being bonded to an atom chosen from hydrogen, the carbon atom already noted, a second carbon atom, the nitrogen atom already noted, a second nitrogen atom, the metal atom already noted in the case of a metal of valence greater than one, a second atom of metal and oxygen when the first valence is not attached to an atom of hydrogen, the proportion of sulphur calculated with reference to the weight of the sulphur compound being between 5 and 99%. Process for stabilizing a phosphoric ester of which the molecule possesses at least one alkyl group containing 1 to 3 carbon atoms characterized in that there is added to the phosphoric ester or to a mixture which contains it, 0.05 to 10% calculated on the weight of the phosphoric acid ester of an agent capable of stabilizing the said phosphoric ester against protonisation and comprising at least one sulphur compound such as that defined thereupon.
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