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Study of the mechanism of the reaction between quinones arenalazines and primary alkylamines
Authors: B.V. Murashevich, K.A. Shreiber, V.M. Miheenko, K.S. Burmistrov, N.V. Toropin
Number of views: 371
A path of the reaction between quinones arenalazines and primary aliphatic amines with the formation of the 1,3,5-substituted 1,2,4-triazoles is suggested. The process of the formation of 1,3,5-substituted 1,2,4-triazoles is multistage and the cyclization occurs as an oxidation process which is accompanied by dehydrogenation of the α-methylene group of amine. In accordance with the proposed reaction path, the first stage of the process is the reaction of 1,8-addition of an amine to azine with the formation of triazene, the last substance existing as two tautomeric forms. The oxidation of triazene by quinoid structure proceeds under the action of atmospheric oxygen. The oxidized form of triazene exists as three prototropic tautomers as well as in the form of a cycle structure; the further oxidation of these structures produces a corresponding 1,2,4-triazole. The participation of atmospheric oxygen in the oxidation process is confirmed by the fact that we discovered a product by thin-layer chromatography when performing the reaction in deaerated solvent, this product being identical to a compound obtained in the reaction between 4-chloro-N-(4-hydroxyphenyl) benzenecarbohydrazonoyl chloride and ethylamine. The heterocyclization with the formation of 1,2,4-triazoles does not occur in a deaerated medium. The scheme is confirmed by the data of spectrophotometric studies, quantum chemical calculations, thin-layer chromatography, and the results of the independent counter synthesis. The structures of intermediate compounds are established. The reaction rate constant is calculated and the rate-determining stage is identified.