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Mechanism of Formation of the Cyano Group from the Chloromethyl, Methoxymethyl, and Alkoxycarbonyl Substituents in the Aromatic Ring Under Conditions of Oxidative Ammonolysis

“…Evidence for this mechanism was provided by quantum-chemical calculations and the experimentally established correlation between the rates of selective oxidation products and the concentration and strength of basic centers [8]. We found a linear correlation between the deprotonation enthalpy of alkyl substituents and the rate constants of their conversion into the cyano group [10,11], which, too, argues in favor of the heterolytic mechanism.The aim of the present work was to find out the reasons for the higher, compared with the methyl group, reactivity and selectivity of the conversion into the cyano group of such heteroatomic substituents in the aromatic ring as chloromethyl, methoxymethyl, and alkoxycarbonyl. We performed quantum-chemical calculations of the electronic structure of the starting compounds and probable intermediate products (radicals, carbanions, and carbocations), as well as simulation of the reaction of the starting compounds with active surface centers of the oxide catalyst in terms of the cluster approach.…”

“…Evidence for this mechanism was provided by quantum-chemical calculations and the experimentally established correlation between the rates of selective oxidation products and the concentration and strength of basic centers [8]. We found a linear correlation between the deprotonation enthalpy of alkyl substituents and the rate constants of their conversion into the cyano group [10,11], which, too, argues in favor of the heterolytic mechanism.…”

Oxidative ammonolysis of 3- and 4-methylpyridines on vanadium oxide catalysts modified with titanium and tin oxides

“…Figure 2 shows data on how the amount of tin dioxide in oxide V-Ti-Sn-O catalysts affects the oxidative ammonolysis of 3-and 4-methylpyridines. It can be seen that, under comparable conditions, the conversion of 4-methylpyridine exceeds that of the 3-isomer, which is due to its higher reactivity [5]. The best catalytic properties in oxidative ammonolysis of methyl pyridines is exhibited by the catalyst of composition V 2 O 5 : TiO 2 : SnO 2 = 1 : 4 : 4, which contains 54.6% SnO 2 : the yields of 3-and 4-cyanopyridines on this sample at a methylpyridine : O 2 : NH 3 molar ratio of 1 : 20 : 1.2 are 90 and 85%, respectively.…”

Oxidative Ammonolysis of Dialkylpyridines

“…Under the conditions used, transformations of the 5-alkyl groups in the subsequent stage were not attended with elimination of the 2-CN group; as a result, both 2,5-lutidine and 2-methyl-5-ethylpyridine gave up to 73% of pyridine-2,5-dicarbonitrile [7]. A kinetic study of the oxidative ammonolysis of 2-methyl-5-ethylpyridine on a V3Ti oxide catalyst showed that the ethyl substituent is much less reactive: Neither 2-methyl-5-vinylpyridine nor 2-methylpyridine-5-carbonitrile were found among the reaction products [8]. Compelling evidence for the reactivity effect of the position of the substituent in the pyridine ring was provided by the results of the oxidative ammonolysis of 2,3-, 2,5-, and 3,4-lutidines on a Cr 2 O 3 (5%)/g-Al 2 O 3 catalyst: At a low conversion (~25%) of the starting compounds, 3-methylpyridine-2-carbonitrile, 5-methylpyridine-2-carbonitrile, and 3-methylpyridine-4-carbonitrile, respectively, were obtained with a selectivity of higher than 90%.…”

“…We made an attempt to estimate, to a first approximation, the enthalpy of proton abstraction from the side groups of dialkylpyridines bound through the nitrogen atom with tetrahedral vanadium clusters of various structure, that simulate Brønsted acid centers of a catalyst surface [15]. The calculation procedure has been described in [4].…”