ethyl 5-allyl-7-methyl-4,6-dioxo-4,5,6,7-tetrahydro-[1,2,3]triazolo[1',5':1,6]pyrazino[2,3-d]pyridazine-3-carboxylate

ethyl 5-(4-bromophenethyl)-7-methyl-4,6-dioxo-4,5,6,7-tetrahydro-[1,2,3]triazolo[1',5':1,6]pyrazino[2,3-d]pyridazine-3-carboxylate

ethyl 5-benzyl-7-methyl-4,6-dioxo-4,5,6,7-tetrahydro-[1,2,3]triazolo[1',5':1,6]pyrazino[2,3-d]pyridazine-3-carboxylate