pyrido[b]azepines, catalytic cyclization, radical reactions, Beckmann rearrangement, cycloalkylations.

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Pyrido[b]azepines are represented in the literature by four types of isomeric structures: pyrido[3,2-b] azepines, pyrido[2,3-b]azepines, pyrido[3,4-b] azepines and pyrido[4,3-b ]azepines. They belong to the structural analogues of 1-benzazepine - an attractive class of heterocycles with a strong pharmacological profile. They are also used as important molecular platforms in the construction of bioactive compounds. Analysis of the literature has shown that compounds that contain the pyrido[b]azepine fragment demonstrate antiviral, antimicrobial, and antitumor activity. They are knownas effective inhibitors of R1P1 kinase, ubiquitin- specific proteases (USPS), cyclin-dependent kinase (CDKS), and glycogen synthase kinase 3 (GSK-3), TRPM8 protein, and angiotensin I type 2 (AT2) receptors. Over the last decade, promising pharmacological properties of pyrido[b]azepine derivatives stimulated the development of fundamentally new methods of their synthesis as well as the improvement of known synthetic approaches. In general, among the various methods for the synthesis of hydrogenated pyrido[b] azepines and their benzanelated analogues, priority is currently given to approaches that include the formation of an azepine cycle via the intermolecular formation of C-N and C-C bonds. These mainly include catalytic cyclizations using cobalt, palladium, and rhodium compounds. Reactions of intramolecular radical difluoromethylarylation and diauryl peroxide-initiated radical azepine analelenization of the pyridine fragment are also of great importance. An interesting method for the synthesis of pyrido [2,3-b] azepin-5-one derivatives was developed on the basis of the Friedel-Crafts intramolecular cycloalkylations reaction.


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