Unusual formation of ( E )-11-(aminomethylene)-8,9,10,11-tetrahydropyrido[2′,3′:4,5]pyrimido[1,2- a ]azepin-5(7 H )-one and its crystal structure

Selective C-formylation of 8,9,10,11-tetrahydropyrido[2′,3′:4,5]pyrimido[1,2- a ]-azepin-5(7 H )-one has been studied for the first time. It was revealed that formylation proceeds by the formation of an intermediate salt, which due to the re-amination process on treatment with aqueous ammonia transformed into the corresponding ( E )-11-(aminomethylene)-8,9,10,11-tetrahydropyrido[2′,3′:4,5]-pyrimido[1,2- a ]azepin-5(7 H )-one, C 13 H 14 N 4 O, as an E -isomer. Formylation was carried out by Vilsmeier–Haack reagent and the structure of the synthesized compound was confirmed by X-ray structural analysis, spectroscopic and LC–MS methods. In the molecule, the seven-membered pentamethylene ring adopts a twist-boat conformation.