Efficient synthesis of α- and δ-carbolines by sequential Pd-catalyzed site-selective C-C and twofold C-N coupling reactions

Two concise and efficient approaches were developed for the synthesis of alpha- and delta-carboline derivatives. The success of the synthesis relies on site-selective Suzuki-Miyaura reactions of 1-chloro-2-bromopyridine or 2,3-dibromopyridine with 2-bromophenylboronic acid and subsequent cyclization with amines which proceeds by twofold Pd-catalyzed C-N coupling reactions.