Alleviating Catalyst Decay Enables Efficient Intermolecular C(sp3)–H Amination under Mechanochemical Conditions

The implementation of an energetically distinct mechanical activation strategy in catalysis has unlocked exciting opportunities for sustainable organic synthesis. Differing from the primary synthetic endeavors to explore reaction diversity that mechanochemistry can substitute the conventional solution-based protocols and probe essential reaction kinetics and thermodynamics, herein we investigate the origin of enhanced catalytic stability and performance under ball milling by taking Rh2(esp)2-catalyzed intermolecular C–H amination as a study case. Significant alleviation of catalyst decay was observed. Mechanistic studies revealed that single-electron oxidation of the RhII dimer and solvent oxidation are largely circumvented, thereby alleviating the decay of metal catalysts. Also, the present work has delineated the first mechanochemical C(sp3)–H amination, which accommodates a host of hydrocarbons and complex natural products with economized precious catalysts under solvent-free conditions, thus substantially enriching the repertoire of mechanosynthesis.