Palladium-Catalyzed Oxidative Synthesis of Unsymmetrical Azophenols

A straightforward palladium-catalyzed oxidative hydroxylation of azobenzenes is reported. The developed methodology tolerates various functional groups and allows the synthesis of diverse unsymmetrical azophenols under mild conditions in good to excellent yields. A complementary procedure was also investigated by in situ generation of PIFA. This study represents the first general method for the synthesis of o-hydroxyazobenzenes starting from simple azoarenes.