The concept of regioorientation is proposed for the annelation of the pyridine ring with the participation of 5-, 6-, and 7-aminoindoles. The conclusions based on the experimental data are supported by quantum-chemical calculations.The production of quinoline and its derivatives is based on various types of pyridine ring closure with the participation of arylamines, hetarylamines, and fl-dicarbonyl compounds [1]. Such processes include a condensation stage in which an enamine E is formed; this subsequently undergoes intramolecular cyclization under conditions of kinetic or thermodynamic control to form a quinoline system:We have investigated the possibility of using 5-, 6-, and 7-aminoindoles in this sort of reaction in order to obtain pyrroloquinolines. Results from this research have been reported in a series of papers . After analyzing the entire body of data, we have formulated a general concept of annelation of the pyridine ring to the benzene ring of the two-ring indole system, by the use of benzaminoindoles.Enamines of aminoindoles undergo cycIocondensation more readily than do the enamines of anilines and naphthylamines. This is manifested most clearly in the acid cyclization of indolylenaminoketones, indolylenaminoaldehydes, and indolylamides of acetoacetic acid. These compounds are cyclized quite smoothly when they are refluxed in trifluoroacetic acid (and in some cases even at room temperature) [2][3][4] 9]. We should emphasize that the formation of a quinoline system when using analogous derivatives of aromatic amines requires heating in concentrated sulfuric acid [1]. This difference is apparently related to the influence of the pyrrole fragment, which not only increases the overall nucleophilicity of the benzene ring in the indoles, but also tends to stabilize the intermediate cation. Substituents in the. pyrrole part of the molecule also influence the overall character of the process. Thus, the enamine of 2,3-dimethyl-5-aminoindole is cyclized in trifluoroacetic acid, even at room temperature; in contrast, cyclization of the analogous enamine of 2-methyl-5-aminoindole requires heating; this difference can apparently be attributed to a difference in the basicity of the compounds in the stage of the processes preceding the cyclization [4].Substituents in the benzene ring of the enamine are not consistent in their influence on cyclization. A methyl group, the same as in the case of anilines, has practically no influence on the course of cyclization; in contrast, the presence of a methoxy group in various positions plays an important role in the ring formation process. Thus, enamines obtained from 7-methoxy-6-aminoindole are converted to pyrroloquinolines just as readily as are the corresponding unsubstituted or methylsubstituted analogs [17]. However, the derivatives of 6-methoxy-5-aminoindoles and 5-methoxy-6-aminoindoles, like the aniMordovian State Pedagogical Institute,

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