- Computational tools for mechanistic discrimination in the reductive and metathesis coupling reactions mediated by titanium(IV) isopropoxide
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A theoretical study has been carried out at the B3LYP/LANL2DZ level to compare the reactivity of phenyl isocyanate and phenyl isothiocyanate towards titanium(IV) alkoxides. Isocyanates are shown to favour both mono insertion and double insertion reactions. Double insertion in a head-to-tail fashion is shown to be more exothermic than double insertion in a head-to-head fashion. The head-to-head double insertion leads to the metathesis product, a carbodiimide, after the extrusion of carbon dioxide. In the case of phenyl isothiocyanate, calculations favour the formation of only mono insertion products. Formation of a double insertion product is highly unfavourable. Further, these studies indicate that the reverse reaction involving the metathesis of N,N ′-diphenyl carbodiimide with carbon dioxide is likely to proceed more efficiently than the metathesis reaction with carbon disulphide. This is in excellent agreement with experimental results as metathesis with carbon disulphide fails to occur. In a second study, multilayer MM/QM calculations are carried out on intermediates generated from reduction of titanium(IV) alkoxides to investigate the effect of alkoxy bridging on the reactivity of multinuclear Ti species. Bimolecular coupling of imines initiated by Ti(III) species leads to a mixture of diastereomers and not diastereoselective coupling of the imine. However if the reaction is carried out by a trimeric biradical species, diastereoselective coupling of the imine is predicted. The presence of alkoxy bridges greatly favours the formation of the d,l (±) isomer, whereas the intermediate without alkoxy bridges favours the more stable meso isomer. As a bridged trimeric species, stabilized by bridging alkoxy groups, correctly explains the diastereoselective reaction, it is the most likely intermediate in the reaction.
- Kumar, Akshai,Samuelson, Ashoka G
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- An Fe3O4@SiO2/Schiff base/Cu(ii) complex as an efficient recyclable magnetic nanocatalyst for selective mono: N-arylation of primary O-alkyl thiocarbamates and primary O-alkyl carbamates with aryl halides and arylboronic acids
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An efficient, convenient and novel method for the selective mono N-arylation of primary O-alkyl thiocarbamates and primary O-alkyl carbamates with aryl halides and arylboronic acids in the presence of a recyclable magnetic Cu(ii) nanocatalyst is described. A variety of mono N-arylated O-alkyl thiocarbamates and O-alkyl carbamates were prepared in good to excellent yields with a broad range of aryl coupling partners. The magnetic nanocatalyst can be easily recovered with an external magnetic field and reused at least five times without noticeable leaching or loss of its catalytic activity. This cost-effective and eco-friendly methodology has some other advantages, such as easy preparation of the catalyst, simple workup procedure, and easy purification, which makes this protocol interesting for the users in various fields of pharmacology and biotechnology systems.
- Sardarian, Ali Reza,Dindarloo Inaloo, Iman,Zangiabadi, Milad
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p. 8557 - 8565
(2019/06/14)
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- Organocatalytic, difluorocarbene-based S-difluoromethylation of thiocarbonyl compounds
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Upon treatment with trimethylsilyl 2,2-difluoro-2-fluorosulfonylacetate (TFDA) and a catalytic amount of N,N,N′,N′-tetramethyl-1,8-diaminonaphthalene, secondary thioamides and thiocarbamates undergo selective difluoromethylation on the sulfur atom to give S-difluoromethyl thioimidates and thioiminocarbonates in good yields, respectively. This is the first report on the synthesis of acyclic difluoromethyl thioimidates and thioiminocarbonates. The key for S-difluoromethylation is the organocatalytic generation of difluorocarbene (:CF2) under mild conditions, which prevents decomposition of the substrates. This process provides an efficient approach to pharmaceuticals and agrochemicals bearing a difluoromethylsulfanyl group, starting from widely available thiocarbonyl compounds.
- Fuchibe, Kohei,Bando, Masaki,Takayama, Ryo,Ichikawa, Junji
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p. 133 - 138
(2015/03/04)
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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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- A facile, safe and inexpensive preparation of S -methyl arylcarbamothioates by methylthiocarbonylation of primary arylamines with O, S -dimethyl carbonodithioate
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O,S-Dimethyl carbonodithioate is proposed as a suitable and safely handled reagent that can be used in the methylthiocarbonylation of primary arylamines to give S-methyl arylcarbamothioates. Optimal conditions involved a one-step procedure that was carried out at 45C in a solvent-free system, in the presence of triethyl(methyl)ammonium S-methyl carbonodithioate as a reaction promoter. The title products were obtained pure in yields that, with one exception, varied between 72 and 91% (average yield of the 12 considered examples was 83%). The by-product S,S-dimethyl carbonodithioate is also a valuable reagent. Georg Thieme Verlag Stuttgart · New York.
- Degani, Iacopo,Fochi, Rita,Magistris, Claudio
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experimental part
p. 1113 - 1122
(2010/05/19)
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- Glycosyl alkoxythioimidates as complementary building blocks for chemical glycosylation
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It is reported that S-glycosyl O-methyl phenylcarbamothioates (SNea carbamothioates) have a fully orthogonal character in comparison to S-benzoxazolyl (SBox) glycosides. This complete orthogonality was revealed by performing competitive glycosylation expe
- Ranade, Sneha C.,Kaeothip, Sophon,Demchenko, Alexei V.
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supporting information; experimental part
p. 5628 - 5631
(2011/03/20)
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- Synthesis and antiproliferative activity of basic thioanalogues of merbarone
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Three series of 5-substituted 1,3-diphenyl-6-(ω-dialkyl- and ω-cyclo-aminoalkyl)thio-2-thiobarbiturates (11-13) were synthesized as polysubstituted thioanalogues of merbarone, a topoisomerase II inhibitor acting on the catalytic site. To better understand pharmacophore requirements, a forth series of conformationally constrained analogues 14 was also prepared. Derivatives 11b,e, 14b,e,h,i,j were active in the low micromolar concentration range (IC50: 3.3-4.3 μM), whereas compounds 11a,c,d,f,h,j and 13a,b,d,g,j and 14a,d,f showed IC50 values between 10 and 15.5 μM. In constrast, compounds 12a-c,g-j, 13e,f,h and 14k were inactive. Cytotoxicity data provided from N.C.I. on selected compounds provided evidence that 11b,d, 13d,g and 14b,d,f,h,i,j were endowed with potent antiproliferative activity against leukemia and prostate cell lines (GI50 up to 0.01 μM). In general, bicyclic derivatives 14 were up to 10-fold more potent than monocyclic counterparts against solid tumor-derived cell lines. SAR studies indicated that, in general, a certain tolerability in length of the alkyl side chains and in shape of distal amines is allowed in the four series, but in the monocyclic derivatives (11-13) antiproliferative activity was strongly affected by the nature of the 5-substituents (COOC2H5>COCH3?C6H 5). Compounds 11b and 14b were also evaluated against KB cell subclones expressing altered levels of topoisomerases or the multidrug resistance phenotype (MDR). In both cases the above compounds showed a decrease in potency. In enzyme assays, 11b and 14b turned out to be inhibitors of topoisonerase II as merbaron.
- Ranise, Angelo,Spallarossa, Andrea,Schenone, Silvia,Bruno, Olga,Bondavalli, Francesco,Pani, Alessandra,Marongiu, Maria Elena,Mascia, Valeria,La Colla, Paolo,Loddo, Roberta
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p. 2575 - 2589
(2007/10/03)
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- Photochemical Isomerization of O-Allyl and O-But-3-enyl Thiocarbamates
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The photochemistry of O-allyl and O-but-3-enyl thiocarbamates has been studied.Photolysis of benzene solutions of O-allyl N-phenylthiocarbamates gave S-allyl N-phenylthiocarbamates.The 1,3-allyl migration from the oxygen to the sulfur involves a concerted process.The same type of 1,3-migration took place in the conversion of O-benzyl N-phenylthiocarbamate into S-benzyl N-phenylthiocarbamate.Irradiation of O-but-3-enylthiocarbamates produced iminooxolanes via aminothietane intermediates.In the case of O-but-3-enyl N-benzoyl-N-phenylthiocarbamates, 3-(benzoylmethyl)-2-phenyliminooxolanes were obtained via a ring opening of the aminothietanes involving a 1,5-benzoyl shift.
- Sakamoto, Masami,Yoshiaki, Mitsuru,Takahashi, Masaki,Fujita, Tsutomu,Watanabe, Shoji
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p. 373 - 378
(2007/10/02)
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- 5-Substituted 2,3-dihydro-6-mercapto-1,3-diphenyl-2-thioxo-4(3H)-pyrimidinones and their 6-(acylthio) derivatives with platelet antiaggregating, antiinflammatory, antiarrhythmic, antihyperlipidemic and other activities
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The synthesis in excellent yields of 2,3-dihydro-6-mercapto-1,3,5-triphenyl-2-thioxo-4(3H)-pyrimidinone 3 and 5-ethoxycarbonyl-2,3-dihydro-6-mercapto-1,3-diphenyl-2-thioxo-4(3H)-py rimidinone 4 by reaction of methyl phenylacetate or diethyl malonate, resp
- Ranise,Bruno,Bondavalli,Schenone,D'Amico,Falciani,Filippelli,Rossi
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p. 551 - 558
(2007/10/02)
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- Triorganophosphinegold(I) Carbonimidothioates
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The title compounds, R3PAuSC(=NPh)OR', R = Et, Ph or Cy and R' = Me, Et, Pr, Pri or Cy, have been prepared and characterized by spectroscopic methods (i.r., 1H and 13C n.m.r. and f.a.b. m.s.) and, in the case of the R = Ph and R'= Me compound,
- Hall, Veronica J.,Siasios, George,Tiekink, Edward R. T.
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p. 561 - 570
(2007/10/02)
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- REACTIONS OF 1-CHLOROALKYL ISOCYANATES WITH THIOURETHANES
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1-Chloroalkyl isocyanates react with thiourethanes to gives N-acylation products, namely, N-(N-alkylidenaminocarbonyl)thiourethanes, which exist in solution in tautomeric equilibrium with S-(1-isocyanatoalkyl)isothiourethanes.These tautomeric transformation occur in the C=N-C azaallylic system involving a new anionotropic migrant, namely, the thiocarbamyl group.The reactions of these tautomeric compounds with water, alcohols, phenol, and primary amines proceed with the participation of the azomethine form, while the reactions with secondary amines involve the isocyanate form.
- Vovk, M. V.,Davidyuk, Yu. N.,Chernega, A. N.,Tsymbal, I. F.,Samarai, L. I.
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p. 1635 - 1643
(2007/10/02)
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- Photochemical Synthesis of 2-Substituted Benzothiazoles
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The photochemical reaction of 1-indolethiocarbanilides 1, di- and tri-substituted thioureas 3-5 and 4,4-dimethyl-2,6-dioxothiocyclohexanecarboxanilides 9 affording the respective benzothiazoles are described.
- Muthusamy, Sengoden,Paramasivam, Rangasamy,Ramakrishnan, Vayalakkavoor T.
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p. 759 - 763
(2007/10/02)
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- INTERACTION BETWEEN PHENYLMETHANEPHOSPHONIC ACID DIETHYL ESTER AND ISOTHIOCYANATES
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Diethyl esters of 1-N-substituted thioamido-phenylmethanephosphonic acids are obtained from O,O-diethyl phenylmethanephosphonate, sodium amide as a metallation agent and alkyl- or arylisothiocyanates.It is established that parallel reactions also occur, resulting in the formation of the respective 1,3-disubstituted thioureas and O-ethylthiocarbamates.These represent the main reaction products in the cases when ethanephosphonic acid diethyl ester is used as a starting reagent.
- Lachkova, Victoria,Petrov, Galin
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p. 227 - 233
(2007/10/02)
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- Observations on the reactions of isocyanoacetate esters with isothiocyanates and isocyanates
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The reactions of the metal salts of α-isocyanoacetate esters with isothiocyanates and isocyanates were examined. The effects of modifying the reaction parameters on the outcome of the reaction (Scheme I) of methyl α-isocyanoacetate (1a) with phenyl isothi
- Solomon, Daniel M.,Rizvi, Razia K.,Kaminski, James J.
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p. 651 - 674
(2007/10/02)
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- KINETIC ANALYSIS OF COMPETITIVE REACTIONS OF ISOTHIOCYANATES WITH HYDROXYL AND ALKOXIDE IONS
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The reaction of isothiocyanates with hydroxyl and alkoxide ions has been followed spectrophotometrically in alkaline aqueous-alcoholic solutions.Both the nucleophiles are added to the carbon atom of isothiocyanate group in a competition reaction.The effec
- Augustin, Josef,Balaz, Stefan
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p. 443 - 452
(2007/10/02)
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- Preparation of Methoxythiocarbonyl Substituted Ureas
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The alkali metal salts 4 of phenylthiocarbamic O-methyl ester (1) yields with phosgene a carbonyl chloride (5), which is a suitable starting material for the preparation of the hitherto unknown group of methoxythiocarbonyl substituted ureas.In its reactio
- Mack, Wilhelm
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p. 165 - 170
(2007/10/02)
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