Mechanocatalytic Oxidation Using Alkoxyamine Mechanophores: Ultrasonication-Triggered Release of TEMPO Catalysts

Mechanocatalysis enables spatial control of reactions within polymeric materials, offering great potential for developing advanced self-healing and self-strengthening materials. However, current systems are predominantly limited to metal- and amine-based catalysts, leaving radical-mediated mechanocatalysis unexplored. Herein, we report a series of alkoxyamine mechanophores that act as latent precursors for 2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPO) radicals, which can further catalyze the aerobic oxidation of alcohols. Upon incorporation into polymer backbones, these mechanophores undergo ultrasonication-triggered homolytic C–O bond cleavage to liberate TEMPO radicals, as supported by electron spin resonance (ESR) spectroscopy. Systematic structure–activity studies reveal that the activation percentages of alkoxyamines are influenced by substituents on the phenyl ring and the carbon atom of the C–O bond, with methyl substitution on the carbon atom enhancing mechanophore activation by 4-fold through stabilization of the benzylic radical. Furthermore, these mechanically generated TEMPO radicals effectively catalyze the oxidation of various alcohols to their corresponding aldehydes in moderate yields. This work establishes the first mechanocatalytic platform that leverages latent radical species for selective chemical transformations, offering new possibilities for designing mechanoresponsive materials.