SYNTHESIS AND MASS SPECTROMETRIC CHARACTERISTICS OF 1-(AMINOARYL)BENZIMIDAZOLES

Abstract

As a result of two-stage synthesis, a number of 1-(aminoaryl)benzimidazoles, potential biologically active substances, were obtained. During the first stage, an aromatic nucleophilic substitution reaction, 2-R-benzimidazoles reacted with halogen-nitroarenes. The process proceeded under mild conditions, this indicates a good nucleophilic properties of benzimidazole. It has been shown that during reduction, depending on the structure of 1-(nitroaryl)benzimidazoles in an acidic medium, in addition to the main process, acid-catalyzed isomerization can occur. Rearrangement was observed during the reduction of 1-(2-nitroaryl)benzimidazoles. The presence of a methyl group at the 2 position of the benzimidazole ring of these compounds hindered the rearrangement. When carrying out the reaction under conditions of heterogeneous catalysis in the reactor for flow hydrogenation, isomerization was also not observed. The use of 1-(4-nitroaryl)benzimidazoles as a substrate resulted in the formation of only one product. The mass spectral characteristics of 1-(aminoaryl)benzimidazoles were studied. The peak attribution of the molecular ion [M]+ was carried out by recording mass spectra with electrospray ionization. Ways of fragmentation of the molecular ion of these compounds under the influence of electron impact are proposed. Characteristic ions are identified. It was established that the fragmentation of the molecular ion of 1-(aminoaryl)benzimidazoles began either by elimination of the substituents, followed by cleavage of the two C—N bonds in imidazole, or by elimination of the HCN fragment of the imidazole ring and further elimination of the substituents. As a result, the formation of the cation radical of N-phenylbenzenediamine with m/z 181 was occurred. The fragmentation of this ion was carried out similarly to aromatic amines via elimination of a neutral HCN molecule. Further decay of alkylarylamine ions led to a group of characteristic fragmentation ions. Thus, mass spectrometry can be effectively used to identify N-aryl substituted benzimidazoles, as well as their decomposition products.