Triazine derivatives R 0655 Pyridazine Derivatives and Related Compounds. Part 12. Synthesis of Some Pyridazino[4',3':4,5]thieno[3,2-d]-1,2,3-triazines. -The utility of 5-aminothienopyridazine-6-carbohydrazide (I) as a synthon for the synthesis of title pyridazinothienotriazine derivatives with potential biological activity is shown. -(DEEB*, A.; KOTB, M.; EL-ABBASY, M.; Phosphorus, Sulfur Silicon Relat. Elem. 180 (2005) 2, 591-599; Dep. Chem., Fac. Sci., Zagazig Univ., Zagazig, Egypt; Eng.) -R. Langenstrassen 26-102