Merging Mechanochemistry With Double Denitrogenation: Pd‐Catalyzed Cross‐Coupling of Arylhydrazides and Arenediazonium Salts

The construction of biaryl scaffolds through transition‐metal‐catalyzed cross‐coupling remains a cornerstone of modern synthetic chemistry; however, most existing methodologies rely on pre‐functionalized organometallic nucleophiles paired with aryl halides, generating stoichiometric metallic waste. In this study, we report the inaugural ball‐milling‐promoted, double denitrogenative, palladium‐catalyzed cross‐coupling of arylhydrazides with arenediazonium tetrafluoroborate salts for the sustainable synthesis of unsymmetrical biaryls. Under optimized mechanochemical conditions, a broad array of electronically and sterically diverse arylhydrazides were coupled with various arenediazonium salts, affording the corresponding biaryl products in good to excellent yields (up to 97%). Notably, this protocol operates under solvent‐free and ligand‐free conditions, with molecular dinitrogen as the sole gaseous byproduct derived from both coupling partners, thereby representing an ideal atom‐economical scenario. The reaction demonstrates wide functional group tolerance, including halides, electron‐donating and electron‐withdrawing substituents, and heterocyclic substrates. Control experiments and preliminary mechanistic investigations indicate that ball milling plays a pivotal role in facilitating dual oxidative C–N bond cleavage and suppressing undesired homocoupling. This work integrates the concept of double denitrogenative coupling with mechanochemical activation for the first time, providing a green and operationally straightforward platform for biaryl synthesis.