Pd(II)-Catalyzed Synthesis of Polycyclic Heteroarenes via an Aminopalladation/C-H Activation/Dealkylation/Decarboxylative Cyclization Cascade.

Until now, cascade reactions involving five-membered C , C -palladacycles rely heavily on Pd(0)-catalyzed C-H functionalization of aryl halides initiated by carbopalladation. Herein, we report a novel Pd(II)-catalyzed cascade decarboxylative cyclization of o -alkynylanilines initiated by aminopalladation. In this protocol, o -alkynylanilines undergo sequential anti aminopalladation, C-H activation, and dealkylation to form C , C -palladacycles, which are then trapped by o -bromobenzoic acids or 8-bromo-1-naphthoic acid to produce diverse polycyclic heteroarenes, such as dibenzo[ a , c ]carbazoles and multiple arene-fused cyclohepta[1,2- b ]indoles.