Investigations on the synthesis and properties of some N-arylpiperazinylalkyl derivatives of 1,4-dioxo (1,4,5-trioxo)-1,2,3,4-tetra (and 1,2,3,4,5,6-hexa)hydropyrido[3,4-d]pyridazines.

2-(1-Piperidino)- and 2-(4-methyl-1-piperazinyl)-6-methyl-3, 4-pyridinedicarboximides (1,2) react with CH3NH-NH2 yielding 3-methyl derivatives of the corresponding 1,4-dioxo-1,2,3,4-tetrahydropyrido[3,4-d] pyridazines (4,5). The same reaction with 1,6-dimethyl-2-oxo-1,2-dihydro-3,4- pyridinedicarboximide (3) affords 2-methyl derivative of the corresponding 1,4,5-trioxo-1,2,3,4,5,6- hexahydropyrido[3,4-d]pyridazine (8. Compounds 4,5 and 8 were transformed into their N-arylpiperazinylalkyl derivatives (13-18) on two ways. Some of them were active pharmacologically.