Pyrimido[4,5-c]pyridazines. 3. Preferential formation of 8-amino-1H-pyrimido[4,5-c]-1,2-diazepin-6(7H)-ones by cyclizations with .alpha.,.gamma.-dioxo esters
1H-Pyrimido-(4,5-c)-1,2-diazepines, methods for their preparation and compositions containing them; their use as intermediates for heterocyclic transformations.