Studies on the chemical transformations of rotenoids. 6 Synthesis and antitumor-promoting activity of [1]benzofuro[2,3-d]pyridazines fused with 1,2,4-triazole, 1,2,4-triazine and 1,2,4-triazepine

[1]Benzofuro[2,3-d]pyridazines fused with 1,2,4-triazole (6 and 7), 1,2,4-t riazine (8-10) and 1,2,4-triazepine (12) were prepared by the ring closure of 4-hydrazino-[1]benzofuro[2,3-d]pyridazine (5), derived from naturally oc curring rotenone. Compounds (1a and 1b) exhibited significant inhibitory ac tivity against 12-O-tetradecanoylphorbol 13-acetate (TPA)-induced Epstein-B arr virus early antigen (EBA-EA) activation in Raji cells. In contrast, the fused [I]benzofuro[2,3-d]pyridazines except 6c and 8 were quite inactive.