Synthesis of a New Scaffold: the 7H,8H-Pyrimido[1,6-b]pyridazin-6,8-dione Nucleus

This paper describes a modified method of preparation of a number of α-aryl-α-(pyridazin-3-yl)-acetonitriles via the C-arylation reaction of the corresponding carbanionsof phenylacetonitriles using 3-chloropyridazine derivatives. KOH and DMSO were used inthe deprotonation process, which made the reaction very simple and safe to perform.Nitriles were obtained in the hydrolysis reaction to the corresponding α-aryl-α-(pyridazin-3-yl)-acetamide derivatives, which were next subjected to cyclization to afford the finalproducts. A number of new derivatives of 7H,8H-pyrimido[1,6-b]pyridazin-6,8-dione weresynthesized in the cyclocondensation reaction of respective α-aryl-α-(pyridazin-3-yl)-acetamides with diethyl carbonate in the presence of EtONa. The structure andcomposition of the new compounds were confirmed by IR, 1H- and 13C- NMR analysesand by elemental C, H and N analysis.