2005
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0
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Analytical Sciences: X-ray Structure Analysis Online
Abstract
antimicrobial,1 anticonvulsant and antidepressant activity. The derivatives of 4,5-disubstituted 1,2,4-triazole are synthesised by intramolecular cyclization of 1,4 disubstitued thiosemicarbazides.2,3 The electronic structures and thiol–thione tautomeric equilibrium of heterocyclic thione derivatives have been studied.4 In the present study, a new 4-allyl-5-pyridin-4-yl-2,4-dihydro3H-1,2,4-triazole-3-thione (3) was synthesized by the reaction of 3-isothiocyanatoprop-1-ene and isonicotinohydrazide (1) through N-allyl-2-isonicotinoylhydrazinecarbothioamide (2). Base-catalysed intramolecular dehydrative cyclization of this intermediate furnished the thione in good yield (75 – 85%). The reaction sequences depicted in Scheme 1 were followed to obtain the new compound. The structures of these compounds were determined by the IR, 1H-NMR and 13C-NMR spectra. A mixture of (1) (0.01 mol) and appropriate 3isothiocyanatoprop-1-ene (0.01 mol) in absolute ethanol (100 ml) was refluxed for 6 h. The solid material obtained upon cooling was filtered off, washed with diethy ether, dried and crystallized from a suitable solvent. Yield 85%; m.p. 500 – 503 K. A stirring mixture of compound (2) (1 mmol) and sodium hydroxide (40 mg, 1 mmol, as a 2 M solution) was refluxed for 6 h. After cooling, the solution was acidified with hydrochloric acid and the precipitate was filtered off. The precipitate (3) was then crystallized from a mixture of ethanole–dioxane. Yield: 85%; m.p.: 495 – 497 K. A summary of the crystallographic information is given in Table 1. The structure was solved by direct methods and refined by least-squares on Fobs by using the SHELXS-97 and SHELXL-97 programs, respectively. The final atomic coordinates and equivalent isotropic thermal parameters for x121 ANALYTICAL SCIENCES 2005, VOL. 21