Platinum-Catalyzed Synthesis of Indoles and Isoquinolines from 2-Alkynylarylamides

Significance

In continuation of the In(OTf)₃-catalyzed synthesis of 1,2-dihydroisoquinolines from 2-alkynylarylaldimines (R. Yanada, S. Obika, H. Kono, Y. Takemoto Angew. Chem. Int. Ed. 2006, 45, 3822), the platinum(II)-catalyzed synthesis of indoles and isoquinolines from isocya­nates 2 is reported. After a Hofmann rearrangement of amides 1 using (diacetoxyiodo)benzene, the resulting isocyanates 2 undergo an intramolecular cyclization into an activated alkyne under PtCl₂ catalysis to give products 3. This methodology was applied to the synthesis of macrocyclic bis(indole) 4 via macrocycle bis(ynecarbamate) 5. Structures 3 and 4 were secured by X-ray crystallographic analysis.