M. Al‐Talib, S. Bataineh, H. Tashtoush
1999
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Journal
Heterocyclic Communications
Abstract
1,3and 1,4-bis (l,3,4-oxadiazole-5(4H)-thione-2-yl) benzenes 2m.p. readily react with aryl aldehydes to give 1,3and 1,4benzene dicarboxvlic acid bis (arvlmethvlene)dihvdrazides 4m(a-e) and 4p(a-e). A mechanism was proposed. Introduction A rapidly growing interest in the synthesis of l,3,4-oxadiazole-5 (4H)-thione derivatives has recently been encountered, this is due to their wide range spectrum of biological activities, and an increasing variety of uses (1-5). The conventional method for the synthesis of l,3,4-oxadiazole-2 (3 H)-thiones consists in the reaction of acid hydrazides with carbon disulfide in ethanolic sodium hydroxide solution (6,7). Only a few reports can be found in the literature describing syntheses and reactions of molecules containing two 1,3,4-oxadiazole-2 (3 H)-thione moieties (8). Here we report the reaction of the title heterocycles with aryl aldehydes. Experimental Melting points are determined on an electrothermal-digital apparatus and are uncorrected. 'H-and C-NMR spectra were recorded on Brucker WP 80-SY, WM250 and AC-250 spectrometers in CDC13 or d-DMSO with tetramethylsilane as an internal standard. Infrared spectra were recorded on a Perkin Elmer FT IR SP-2000 spectrometer as KBr pellets. Mass spectra were determined on a double focusing VG 7070E mass spectrometer. Elemental analyses were performed at M.H.W. laboratories. Phoenix, Arizona, USA. Materials 1,3and 1,4-Bis (l,3,4-oxadiazol-5 (3H) thione-2-yl) benzene were prepared following literature procedure (9). Chemicals were purchased from Aldrich and Fluka and used without further purification. General procedure for the preparation of compounds 4. A solution of precursor 2q (3.6 mmol) and the appropriate aryl aldehyde 3a-e (7.2 mmol) in absolute ethanol (50 ml) was heated under reflux for 12 hours. The solid was Filtered and recrystallized from dimethylsulfoxide / water (1/4). The reactions of 2m with 3a-e were carried out in ethylene glycol under reflux. Products were recrystallized from tetrahydrofuran. Tables 1 and 2 include the physical and spectroscopic properties of these compounds.