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

Selective C-formylation of 8,9,10,11-tetrahydropyrido[2 ',3 ': 4,5] pyrimido[1,2-a]azepin-5(7H)-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(7H)-one, C13H14N4O, 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 LCMS methods. In the molecule, the seven-membered pentamethylene ring adopts a twist-boat conformation.