Palladium-Catalyzed Selective Aryl Ring C-H Activation of N-Acyl-2-aminobiaryls: Efficient Access to Multiaryl-Substituted Naphthalenes

Palladium-catalyzed cycloaromatization of N-acyl-2-aminobiaryls, through a sequence of ortho C-H bond activation/alkyne insertion/meta C-H bond activation/alkyne insertion, was developed. An efficient synthesis of multiaryl-substituted naphthalenes, N-[2-(5,6,7,8-tetraarylnaphthalen-1-yl) aryl] acetamides, was demonstrated using molecular oxygen as the sole oxidant. Furthermore, through Buchwald's synthetic protocol, two compounds were converted into corresponding fluorescent carbazoles in 30-40% yield by intramolecular C-N bond formation.