Synthesis of Some New Pyrimidothienopyridazines and Related Heterocycles

5-Amino-3,4-diphenylthieno[2,3-c]pyridazine-6-carbonitrile 2a was reacted with propylene diamine to give tetrahydropyrimidinyl derivative 3. The latter compound (3) underwent certain cyclocondensation reactions to produce pyrimidothienopyridazines 4–6. Also, the reactions of 5-amino-3,4-diphenylthieno[2,3-c]pyridazine-6-carboxamide with heterocyclic aldehydes and/or cycloalkanones were carried out and their products were identified. Moreover, some novel pyridazinothienopyrimidobenzimidazoles 14–17 were synthesized.