T. Maruthikumar, P. Hanumantha Rao,
2003
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Journal
Heterocyclic Communications
Abstract
Mild treatment of 4-arylidene-2-methyloxazoline-5-ones and 4-arylidene-2-phenyloxazoline-5-ones with hydrazine hydrate gave corresponding cinnamhydrzides. These with excess acetic anhydride gave the title 1,2,4triazines. Introduction A large number of uses were recorded in the literature for the 1,2,4-triazine ring system. Impressive results were obtained in their faction as anti-bacterials, antimalarials, anti-inflammatory agents," antivirals," antipsoriatics,' antihypertensives,' antiarthritics and coccidiostats. Other significant industrial attention was also paid to the triazines as pestisides, synthetic high polymers, chemical coatings, photographic fogging agent, dyes and intermediates in platsic manufacture. As a result of their demonstrated usefulness in many applications, and incontinuation of our interest in synthesizing various heterocyclic ring systems,'" we herein report a novel synthesis 1,2,4-triazines. Discussion Treatment of 4-(4-fluorobenzylidene-2-methyloxazoline-5-one ( la) with hydrazine hydrate in ethanol at room temperature gave a-acetamido-4-flurocinnamhydrazide (2a). Refluxion of (2a) with acetic anhydride gave light yellow crystalline compound m.p. 196°C (TLC single spot in ethylacetate). Mass spectrum of it revealed the molecular ion peak at m/z 261, corresponding to the molecular formula C13H12N3FO2. IR spectrum (KBr) indicates the presence of absorptions at 3294 cm" (NH) and 1720 cm-1 (δ-lactamic carbonyl). "H NMR (CDC13) revealed signals at δ 2.2 (s, 3H, CH3), 2.4 (s, 3H, COCHj), 7.1-8.3 (m, aromatic), 8.4 (br, 1H, NH, D 2 0 exchangeable). Based on the spectral data the strecture of the compound has been assigned as 2-acetyl-3-methyl-6-oxo-5-(4-fluorophenylmcthylene)-l//-l,2,4triaziene (3a). The formation of the 3 can be best explained on the basis of attack of acetic anhydride on the primary amino group of 2 resulting in the unstable intermediate 4. It readily undergoes dehydrative cyclization in the presence of acid * To whom correspondence should be addressed (Previous name was P. Hanumanthu)