Synthesis and structures of 4,6-disubstituted 2-(5-methyl-1,2,4-oxadiazol-3-yl)-1,3,5-triazines

Abstract

New 1,2,4 oxadiazolyl 1,3,5 triazines were synthesized from amidoximes derived from sym triazine mononitriles. The structure of one of the resulting compounds was studied in detail by X ray diffraction.Key words: amidoximes of the sym triazine series, 4,6 disubstituted 2 acetoxyamidino 1,3,5 triazines, 4,6 disubstituted 2 (5 methyl 1,2,4 oxadiazol 3 yl) 1,3,5 triazines, cy clization.1,2,4 Oxadiazole and sym triazine derivatives possess a wide spectrum of biological activities. 1-3 It was of inter est to synthesize new compounds containing both these heterocycles.We synthesized (Scheme 1) oxadiazolyltriazines 4 from nitriles 1. Amidoximes 2a-i were prepared by the reac tion of nitriles 1 with a 20% excess of hydroxylamine in an water ethanol solution.It is known 4,5 that the hydroxy group in aromatic amidoximes smoothly reacts with carboxylic acid an hydrides and chlorides to form the corresponding acylated derivatives. The reactions of compounds 2a-i with acetyl and isobutyroyl chlorides, which were used in a 5% excess with respect to the stoichiometric amount, under mild conditions (solutions in anhydrous benzene, 5-20 °C) in the presence of an excess of pyridine produced acylated derivatives 3a-m.Refluxing of solutions of compounds 3a-m in glacial acetic acid for 2-5 h smoothly afforded the correspond ing substituted 1,2,4 oxadiazolyl 1,3,5 triazines 4a-m in good yields.The crystal structure of one of the resulting oxa diazolyl 1,3,5 triazines, viz., compound 4d containing the amino and diethylamino groups at positions 4 and 6 of the triazine ring, was established by X ray diffraction study of a single crystal grown from ethanol. A projection of the crystal structure of compound 4d is shown in Fig.

Oxadiazoles

“…Another different general synthetic route is based on the 1,3-dipolar cycloaddition of nitrile oxides to nitriles, developed by Leandri (cycloaddition route) [180]. The cyclization of O-acylamidoximes is performed by heating them at their melting point [185], or at reflux in a high-boiling solvent (DMF [186], toluene [187], pyridine [188], ethanol [189], acetonitrile [190], glacial acetic acid at reflux) [191,192], eventually in the presence of a dehydrating agent (phosphorous pentoxide, phosphorus oxychloride, or acetic anhydride).…”

Synthesis of new 4,6-disubstituted-1,3-5-triazin-2-yloxy esters and N-hydroxyamides

“…Compounds IIIc and IVc have the maximum intensity of the molecular ions. The fragmentation pattern of the molecular ions under electronic impact is the same as has been observed for the synthesized heterocyclic derivatives of the 1,3,5-triazine [36,37,[40][41][42][43].…”

Synthesis and structure of new 1,2,3-triazolyl substituted 1,3,5-triazines

“…An even more exoticly connected heterocyclic aromatic system containing 1,3,5-triazine and 1,2,4-oxadiazol cycles has been synthesized by our group and reported recently [12].…”