Alkyl 1H-pyrrole-2-carboxylates and dialkyl 1H-pyrrole-2,5-dicarboxylates were synthesized in quantitative yield by reactions of 1H-pyrrole, 2-acetyl-1H-pyrrole, and 1-methyl-1H-pyrrole with carbon tetrachloride and aliphatic alcohols in the presence of iron-containing catalysts. A probable reaction mechanism was proposed, and the rate constants and energies of activation of particular steps were determined on the basis of experimental data.Pyrrolecarboxylic acids attract strong interest as starting compounds for the synthesis of porphyrins and biologically active substances [1,2]. For instance, pyrrole-2-carboxylic acid derivatives exhibit antiviral activity, in particular against classical bird influenza viruses [3], whereas 5-arylpyrrole-2-carboxylic acid sodium salts were found to possess anticonvulsant activity [4].A specific feature of pyrrolecarboxylic acids is that the carboxy group therein, regardless of its position, can readily be replaced by other functional groups. Replacement of carboxy group by the action of electrophilic reagents occurs more readily than replacement of hydrogen [5,6]. For example, nitration of pyrrolecarboxylic acids with nitric acid in acetic anhydride gives mixtures of nitropyrrolecarboxylic acids and 2-nitropyrrole. The carboxy group in pyrrole-2-carboxylic acid is replaced most smoothly by halogen atoms.Published data on the synthesis of pyrrolecarboxylic acids, in particular of an important representative of this series of compounds, 5-acetyl-1H-pyrrole-2-carboxylic acid, are very few in number. Difficulties in the synthesis of this acid are related to the effect of a strong electron-withdrawing substituent (COOH, COOCH 3 , COCH 3 ) in position 2 of the pyrrole ring, which changes the regioselectivity intrinsic to pyrrole in electrophilic substitution reactions; as a result, a new substituent enters position 4 rather than free position 5 [6,7]. Only in the reaction with tert-butyl hypochlorite, the desired 5-chloro-1H-pyrrole-2-carboxylic acid was obtained; this reaction is a very rare example of radical replacement in the pyrrole ring [8].The goal of the present work was to develop a general procedure for the introduction of a carboxy group into compounds of the pyrrole series via reaction with the system CCl 4 -MeOH-catalyst. We showed previously [9] that such reaction is successful with thiophene and its derivatives [9]. As model substrate we used 2-acetyl-1H-pyrrole. We found that the reaction of 2-acetyl-1H-pyrrole with carbon tetrachloride and methanol in the presence of a catalyst is regioselective and that the only product is methyl 5-acetyl-1H-pyrrole-2-carboxylic acid (Ia). As catalysts we used Ni, Cu, Mn, Pd, V, and Fe compounds and complexes which are known to activate C-Cl bond in CCl 4 molecule [9, 10]. The highest catalytic activity was observed for the following iron compounds: Fe(OAc) 2 , Fe(C 5 H 5 ) 2 , FeBr 2 , and Fe(acac) 3 . The optimal conditions were temperature 115°C and reaction time 6 h; in this case the conversion of initial 2-acetyl-1H-pyrrole wa...
This article discusses the main problems associated with information security in corporate networks and ensuring the reliable operation of information systems and the services they provide. Information security is understood as the security of information resources and information systems, as well as the supporting infrastructure from accidental or deliberate influences of a natural or artificial nature, fraught with harm to the owners or users of information resources. Currently, there are major changes in information security issues. They relate to the methods of work of attackers, the conditions of crimes commited in the computer sphere, as well as the consequences of illegal activities.
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