Unveiling the Hidden\nReactivity in the <i>N</i>‑Heterocyclic Carbene-Catalyzed\nAerobic Oxidation of Aldehydes:\nUnlocking Its Powerful Catalytic Performance

An\ninnovative solution that overcomes the long-standing inherently\nlow efficiency in <i>N</i>-heterocyclic carbene-catalyzed\naerobic oxidation of aldehydes is reported. This solution included\nthe design and synthesis of a novel polymerized catalyst and the utilization\nof a flow reactor. The unprecedentedly high efficiency achieved via\nthis protocol makes it synthetically applicable. A total turnover\nnumber (TON) of 26,300 was achieved based on recycling experiments\n(runs). The highest TON in a single run could be up to 2475 with a\nturnover frequency (TOF) of 208 h<sup>–1</sup>, far superior\nto its traditional counterpart, in which a typical TON ranges from\n20 to 100 with a TOF of less than 10 h<sup>–1</sup>. The catalyst\nhas been recycled over 50 times and is still fully active. The success\nwas attributed to the discovery of hidden reactivity, which was observed\nfor the first time as an autoacceleration in the reaction rate during\nkinetic investigations. The research also provided concrete evidence\nsupporting the conclusion that radical intermediates played crucial\nroles in the catalytic cycle by having a determinative impact on the\noverall reaction rate.