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

Abstract

Until now, cascade reactions involving five-membered <i>C</i>,<i>C</i>-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 <i>o</i>-alkynylanilines initiated by aminopalladation. In this protocol, <i>o</i>-alkynylanilines undergo sequential <i>anti</i> aminopalladation, C-H activation, and dealkylation to form <i>C</i>,<i>C</i>-palladacycles, which are then trapped by <i>o</i>-bromobenzoic acids or 8-bromo-1-naphthoic acid to produce diverse polycyclic heteroarenes, such as dibenzo[<i>a</i>,<i>c</i>]carbazoles and multiple arene-fused cyclohepta[1,2-<i>b</i>]indoles.