Bis‐Pyrazolones as azodienophiles

Lead tetraacetate oxidations of 2,3,3a,4,6,7,7a,8‐octahydrobenzo[1,2‐ c :4,5‐ c ']dipyrazolo‐3,7‐dione and 2,3,3a,4,5,5a,6,7‐octahydrobenzo[2,1‐ c :3,4‐ c ']dipyrazolo‐3,6‐dione in the presence of 1,3‐cyclopentadiene, 1,3‐cyclohexadiene, 2,3‐dimethyl‐1,3‐butadiene or 1,4‐diphenyl‐1,3‐butadiene have yielded octahydrodipyridazino[1,2‐ a :1,2‐ a ']benzo[1,2‐ c :4,5‐ c ']dipyrazolo‐6,14‐diones and octahydrodipyridazino[1,2‐ a :1,2‐ a ']benzo[2,1‐ c :3,4‐ c ']dipyrazolo‐6,9‐diones. In one of the eight Diels‐Alder reactions two isomeric products were isolated.