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Pyrylium salts are interesting systems for studying reaction with nucleophilic reagents [1, 2]. The functional groups in the cation affect the electronic structure and consequently the chemical properties of these salts, and participate in ring formation processes [3,4]. In continuing research on synthesis and conversions of condensed pyrylium salts [5, 6], we have studied the reactions of 3-arylaminobenzofuro-(1), 3-arylaminobenzothieno-(2), and 3-arylaminoindolo[2,3-c]pyrylium (3) perchlorates with nucleophilic reagents. With the aim of determining the effect of the arylamino group on the reactivity of the pyrylium ring condensed with different benzannelated heterocycles, we have calculated the electronic structure parameters of salts 1a-3a within the coupled multiparameter perturbation theory of the PPP method [7,8]. The parameters of the π-electron Hamiltonian and the resonance integrals are analogous to those assumed for the carbon and nitrogen atoms [9, 10] and the oxygen atom of the furan ring [11], and the thiophene sulfur atom in [12]. The effect of substituents on the electronic structure parameters of the compounds was taken into account within perturbation theory describing chemical substitution [13].Based on analysis of the electronic structure parameters of the cations for salts 1a-3a, we showed that charge localization is observed mainly in the pyrylium ring and on the hetero atoms O, N, and it decreases somewhat as we go to the corresponding anhydro forms of these compounds 4a-6a.

Keywords: 2-aminoindolo[2,3-c]pyridin-3(2H)-one, hydrazine hydrate, hydrazones of 2-acetyl-3-indolylacetic acid, 2,3-dihydro-2-oxo-5-R 1 -1H-[1,2]diazepino [4,5-b]indoles.Interest in derivatives of 2,3-benzodiazepines is related to the broad spectrum of their biological action on the central nervous system [1][2][3][4][5][6][7]. Some 2,3-benzodiazepines have been found to be tranquilizers and anticonvulsants [2][3][4]. The tranquilizer, Tofizopam, a 2,3-benzodiazepine, has found use in clinical practice [1]. Considerable attention has been given to the synthesis and study of the pharmacological properties of diazepines condensed with various heterocyclic systems [3,4,6].A number of pathways have been reported for the synthesis of derivatives of 2,3-benzo-4-diazepinones based on the reaction of 2-aroyl-4,5-dimethoxyphenylacetic acids with hydrazine [2,[8][9][10]. 3H-[1,2]Diazepino [5,6-b]indoles were obtained by the cyclization of the ethyl esters of 2-formyl-and 2-acetyl-2-indolylacetic acids using hydrazine hydrate [11][12][13].We have recently shown that the reaction of 2-acetylbenzo[b]furan-3-acetic acid as well as its ester and amide derivatives with hydrazine hydrate leads not to the corresponding benzofurodiazepines but rather to 2-aminobenzofuro[2,3-c]pyridin-3(2H)-ones or azines of 2-acetylbenzo[b]furan-3-acetic acid [14].

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