A. D. Kagarlitskii, L. A. Krichevskii, A. Amirkhanova
Jul 1, 1999
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Influential Citations
4
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Journal
Pharmaceutical Chemistry Journal
Abstract
Compounds of the pyrazine series, including pyrazinecarboxylic acid amides, are widely used in the production of various drugs. One of the well known compounds in this seties is 2-pyrazinecarboxylic acid amide, known as the antituberculous drug pyrazinamide. We have established that this drug can be synthesized with a high yield by oxidative ammonolysis of 2-methylpyrazine [1]. It was found that the process, proceeding in an aqueous ammonia solution, involves oxidation of the methyl group to nitrile, followed by its conversion into amide in the course of high-temperature hydrolysis. By the same token, during oxidative ammonolysis of 2,5-dimethylpyrazine (I) on a molybdenumcerium titanium mixed oxide catalyst, the initial compound converted sequentially into 5-methylpyrazine-2-carboxamide (II) and 2,5-pyrazinedicarboxamide (III) [2]. Below we present the results of investigation of the oxidative ammonolysis of compound I in the presence of three samples of catalysts representing a molybdenum-antimony -titanium mixed oxide system. The samples had the same molar ratio MoO3/Sb203 = 1 : 0.5 and a variable relative content of TiO2: 0.25, 0.50, and 0.75 mole TiO2 per mole MoOs. Selection of this catalyst system was based on the known facts evidencing that the presence of antimony oxides markedly facilitates the oxidative ammonolysis of organic compounds [3, 4]. Antimony oxides favor the activation of oxygen supplied from the gas phase to the contact zone [5] and, under certain conditions, may generate or regenerate active centers on the surface of MOO3, acting by a mechanism of the "remote control" type [6]. The results obtained in our experiments indicate that the oxidative ammonolysis of compound I involves both the for-