Source of materialAcetophenone (6 mmol) was added to an absolute ethanol solution (20 ml) of 4-amino-3-(2-ethoxyphenyl)-1H-1,2,4-triazole-5-thione (4 mmol), which was prepared according to the literature [1]. The pH value then was adjusted to 5-6 with diluted HCl, and the appropriate activated molecular sieves (4 Å) were added. The mixture was stirred and refluxed for 6 hours under a nitrogen atmosphere, and then filtered through celite, and the celite was washed with ethanol. The filtrate was evaporated in vacuo and the crude product was dissolved in as a little ethanol as possible, kept at room temperature. Colorless crystals were separated from the filterate after two days. IR and NMR data are available in CIF.
DiscussionIn recent years, many researchers have paid more attention to some Schiff's bases bearing aryl groups or heterocyclic residues, which possess excellent biological activity [2][3][4]. In particular, triazoles and their heterocyclic derivatives have been reported to be used as drugs and to have considerable biological activities [5][6][7][8][9][10]. 3-Substituted-4-amino-1,2,4-triazole-5-thione is an important block in synthetic heterocyclic chemistry. Interesting in developing new Schiff bases with promising biological activities, we focused our work on reacting the amino group of 3-substituted-4-amino-1,2,4-triazole-5-thione with aromatic aldehydes and attaching active groups on to the 3-position. Up to now, no literature survey revealed that this amino group reacts with aromatic ketones.The present results show that the configuration of the title molecule is E ( figure, top) at the azomethine C=N bond. The C10-S1 bond length (1.677(3) Å) is far shorter than the regular covalent single C-S bond (1.819 Å). Though it is a bit longer than the S=C double bond (1.646(5) Å) [11], it exerts substantial doublebond character, which can be indirectly proved by 1 H NMR (d13ppm N 2-H) [12]. We consider the thion form as the more stable for the title molecule. The five-membered triazole ring (N1, N2, N3, C9, C10) and the two benzene rings (C3-C8) and (C12-C17) are planar in nature, and are hardly distorted from planarity with r.m.s. deviations of 0.012 Å, 0.018 Å, 0.010 Å, respectively. The dihedral angles between the triazole ring and the benzene ring (C3-C8) and between the triazole ring and the benzene ring (C12-C17) are 67.59°and 38.97°, respectively (figure, bottom).