SIMPLE SYNTHESIS OF PRATOSINE AND HIPPADINE BY INTRAMOLECULAR PALLADIUM-CATALYZED CYCLIZATION AND DECARBOXYLATION

The palladium-catalyzed cyclization of dimethyl 1-(2-bromo-4,5-dimethoxybenzyl)indole-2,3-dicarboxylate in the presence of tetrakis(triphenylphosphine)palladium(0) and potassium acetate in hot 1,4-dioxane produced the 7H-pyrrolo[3,2,1-de]phenanthridine derivative, which was converted to pratosine by hydrolysis and decarboxylation. In a similar manner, hippadine was also prepared.