- Les magnesiens allyliques comme agents de fonctionnalisation symetrique ou dissymetrique en 2 et 5 du 1,3,4-thiadiazole
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Allylic Grignard reagents easily react through addition and elimination, with the two methylthio groups of 2,5-bis(methylthio)-1,3,4-thiadiazole, and with the one methylthio group of 5-methylthio-1,3,4-thiadiazol-2(3H)-thione, to lead to symmetrical or unsymmetrical disubstituted derivatives of 1,3,4-thiadiazole.Key words: Magnesium; Thiadiazole; Addition-elimination reaction
- Laduranty, Joelle,Miginiac, Leone
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- 5-Mercapto-1,3,4-thiadiazole-2(3H)-thione: Synthesis and structure of alkylated derivatives
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The observed structure of 1,3,4-thiadiazolidine-2,5-dithione (also known as 2,5-dimercapto-1,3,4-thiadiazole) has been previously reported in three different tautomeric forms including - dithiol and - dithione. This report examines the relative stability of each form and also reports synthesis and characterization of the structures of mono-alkylated and di-alkylated forms of 5-mercapto-1,3,4-thiadiazole-2(3H)-thione. The methods of X-ray crystallography, NMR spectroscopy, and ab initio electronic structure calculations were combined to understand the reactivity and structure of each compound.
- Mistry, Jigar K.,Dawes, Richard,Choudhury, Amitava,Van De Mark, Michael R.
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p. 747 - 754
(2014/06/10)
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- UV-induced transformations of matrix-isolated 1,3,4-thiadiazole-2-thiones
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Monomers of 5-mercapto-1,3,4-thiadiazole-2-thione (bismuthiol) were studied using an experimental matrix-isolation technique as well as by carrying out theoretical quantum chemical calculations. The calculations, performed using the quadratic configuration interaction method with single and double excitations (QCISD)/6-31++G(d,p)//DFT(B3LYP)/ 6-311 ++G(2d,p), predict that the thione-thiol tautomer of bismuthiol should be significantly (by more than 19 kJ mol-1) more stable than other tautomeric forms. Accordingly, only the signatures of the thione-thiol tautomer were observed in the FT-IR spectrum of bismuthiol, recorded directly after deposition of an Ar matrix. UV (l> 320 nm) irradiation induced the conversion of the thione-thiol tautomer into the dithiol form. Analogous investigations were carried out for two related compounds: 5-methyl-1,3,4-thiadiazole-2-thione and 5-methylthio-1,3,4-thiadiazole-2-thione. For these two species, only the thione tautomeric forms were observed after deposition of Ar matrices. These tautomers were predicted (by QCISD calculations) to be more stable (by at least 19kJmol-1) than other tautomeric forms. Upon UV irradiation, the most stable thione forms of these compounds were transformed into the corresponding thiol tautomers. Direct observation of the thione! thiol phototautomeric processes provides a clear proof that intramolecular proton transfer reaction can occur in molecules, such as bismuthiol, in spite of the increased NH...S distance, in comparison to other phototautomerizing species studied so far. All the isomers of the studied compounds (substrates and products of the photoreactions) were identified by comparison of their IR spectra with the spectra calculated at the DFT(B3LYP)/6-311 ++G(2d,p) level of theory for possible isomeric structures. Copyright
- Rostkowska, Hanna,Lapinski, Leszek,Nowak, Maciej J.
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experimental part
p. 56 - 66
(2010/07/08)
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- Dipolar cycloaddition reactions of nitrilimines
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A series of γ-substituted α-methylidene-γ-butyrolactone derivatives underwent regiospecific 1,3-dipolar cycloaddition with N-methyl-C-phenylnitrilimine. These reactions proceeded regiospecifically and with high diastereoselectivity, generally favouring the anti diastereomer as determined by n.m.r, spectroscopy and semiempirical molecular orbital calculations. The assignment for one product was confirmed by X-ray crystallography. N-Methyl- C-phenylnitrilimine underwent regiospecific cycloaddition with a range of C=S-containing dipolarophiles. Substituted thioureas were generally unreactive as dipolarophiles, while 5-thio-substituted 1,3,4-thiadiazole-2(3H)-thiones underwent ready reaction to produce, rather than the expected cycloadducts, complex rearrangement products. The structure of one of these unusual products has been confirmed by X-ray crystallography. A series of disubstituted nitrilimines underwent regiospecific cycloaddition with thiobenzophenone; the structures of the products were confirmed by X-ray crystallography.
- Dunstan, James B. F.,Elsey, Gordon M.,Russell, Richard A.,Paul Savage,Simpson, Gregory W.,Tiekink, Edward R. T.
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p. 499 - 509
(2007/10/03)
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- S,S'-and S,N-Disubstituted Derivatives of 1,3,4-Thiadiazoledithiones
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Facile synthesis of 2-n-dodecylthio-4-phenylthiomethyl-1,3,4-thiadiazole-5-thione 6, starting from 2,5-dimercaptothiadiazole via 2-n-dodecylthio-1,3,4-thiadiazole-5-thione 2, 2-n-dodecylthio-4-hydroxymethyl-1,3,4-thiadiazole-5-thione 4 and 2-n-dodecylthio-4-chloromethyl-1,3,4-thiadiazole-5-thione 5 is described.
- Katritzky, Alan R.,Wang, Zouquan,Offerman, Rick J.
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p. 139 - 142
(2007/10/02)
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- Synthesis, 1H NMR Spectral Properties and Conformational Preferences of some Open-chain and Cyclic Aromatic Sulphides Containing Pyridine or 1,3,4-Thiadiazole Units
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The conformational preferences in solution of eight new open-chain and cyclic aromatic sulphides containing pyridine or 1,3,4-thiadiazole units have been investigated, parallel to those of some structurally related phenyl sulphides, by means of 1H NMR spectroscopy.The results obtained have shown that replacement of phenyl by the pyridyl or the 1,3,4-thiadiazolyl moieties induces slightly different propeller arrangements, ascribed to the higher conjugative tendency of both electron-deficient heteroaromatic rings, in all open-chain mixed sulphides, in opposition to the skew arrangements observed for phenyl sulphide derivatives.No prominent differences have been found for cyclic sulphides, which preferentially adopt the sterically unhindered saddle shape conformation.
- Bottino, Francesco,Pappalardo, Sebastiano
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- New broad spectrum alkylthio cephalosporins
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A series of 7 substituted alkyl thio acylaminocephalosporins were prepared and tested for in vitro antibacterial activity. The authors tried in their research to find any relationship between antibacterial activity and pharmacokinetic properties on the one hand, and chemical structure on the other. The most interesting products were also studied for their in vivo antibacterial activity in experimental acute systemic infections in the mouse.
- Nannini,Molgora,Biasoli
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p. 343 - 352
(2007/10/05)
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