Pd-catalyzed dehydrogenative arylation of arylhydrazines to access non-symmetric azobenzenes, including tetra- <i>ortho</i> derivatives

Azobenzenes are photoresponsive compounds widely used in molecular switches, light-controlled materials, and sensors, but despite extensive studies on symmetric derivatives, efficient methods for synthesizing non-symmetric analogues remain scarce due to regioselectivity issues, multistep procedures, and limited applicability to tetra-<i>ortho</i>-substituted structures. Herein, we describe a direct, one-pot Pd-catalyzed dehydrogenative C-N coupling between aryl bromides and arylhydrazines to access non-symmetric azobenzenes. The use of bulky phosphine ligands and sterically tuned substrates promotes selective N-arylation at the terminal nitrogen. The protocol tolerates a wide range of functional groups and enables the synthesis of well-decorated azobenzenes, including tetra-<i>ortho</i>-substituted derivatives. Notably, the reaction proceeds under an O₂ atmosphere and in the presence of water, highlighting its robustness.