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-triazine (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 occurring rotenone. Compounds (1a and 1b) exhibited significant inhibitory activity against 12-O-tetradecanoylphorbol 13-acetate (TPA)-induced Epstein-Barr 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.