- Desulfurization strategy in the construction of azoles possessing additional nitrogen, oxygen or sulfur using a copper(I) catalyst
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A tandem and convergent approach to various N-, O-, or S-containing azoles has been developed by exploiting the thiophilic property of copper( I) iodide used in a catalytic quantity. The present protocol gives access to amino-substituted tetrazoles, triazoles, oxadiazoles and thiadiazoles via oxidative desulfurization of their respective precursors followed by inter- or intramolecular attack of suitable nucleophiles. For aminotetrazoles and triazoles an excellent regioselectivity has been achieved through proper tuning of the pKa values of the parent amines attached to unsymmetrical thioureas. The method represents an autocatalytic process in which copper( I) iodide gets converted to copper(II) sulfide which in turn transforms to active copper(II) oxide that effectively carries forward the catalytic cycle. The fate of the copper catalyst has also been studied using scanning electron microscopic (SEM) and energy-dispersive X-ray spectroscopic (EDS) analyses which give an insight into the mechanism for this catalytic process.
- Guin, Srimanta,Rout, Saroj Kumar,Gogoi, Anupal,Nandi, Shyamapada,Ghara, Krishna Kanta,Patel, Bhisma K.
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p. 2757 - 2770
(2013/01/15)
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- Studies on Decarboxylation Reactions. Part 6. Kinetic Study of Decarboxylation of 5-Amino-1,3,4-oxadiazole-2-carboxylic Acid and its N-Phenyl Derivatives at High Hydrochloric Acid Concentrations
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The dissociation constants (K1) of both acids 4a-c and esters 5a-c and the rate constants of the decarboxylation reaction of acids 4a-c have been measured at various high concentrations of hydrochloric acid (0.5-8.0 M range).The results obtained have enabled us to suggest the probable structure of the zwitterion which undergoes decarboxylation.
- Noto, Renato,Werber, Giuseppe,Buccheri, Francesco,Arnone, Caterina
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p. 1457 - 1459
(2007/10/02)
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- Base-catalysed Rearrangement of 2-Phenylamino-1,3,4-oxadiazole into 4-Phenyl-1,2,4-triazolin-5-one
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The behaviour in alkaline media (water, water-dioxane, or water-dimethyl sulphoxide) of 2-phenylamino-1,3,4-oxadiazole (IH) has been studied, together with the title reaction.Chemical and kinetic evidence support the occurence of a ring conversion through an intermediate cyclic compound (IV-), followed by the formation of an open-chain anion (V-) that cyclizes fast to the triazole derivative (III-).
- Noto, Renato,Buccheri, Francesco,Werber, Giuseppe,Consiglio, Giovanni,Spinelli, Domenico
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p. 537 - 540
(2007/10/02)
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- Studies on Decarboxylation Reactions. Part 4. Kinetic Study of the Decarboxylation of Some N-Alkyl- or N-Phenyl-Substituted 5-Amino-1,3,4-oxadiazole-2-carboxylic Acids
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The rate constants of the decarboxylation reaction of compounds (Ib-f) have been measured in water over a range of proton activities, at various temperatures.The results obtained strongly support the unimolecular decarboxyprotonation mechanism.
- Noto, Renato,Buccheri, Francesco,Consiglio, Giovanni,Spinelli, Domenico
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p. 1627 - 1630
(2007/10/02)
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