Mild Water-Extruding C(sp3)–O Bond Functionalization with a Modifiable Pyridinium Salt via Dearomatization/Rearomatization Catalysis

Despite the abundant C(sp3)–O bond-rich feedstocks in nature, catalytic transformations of these resources remain challenging due to the difficulty of C–O bond cleavage. Available strategies rely heavily on stoichiometric sacrificial oxygen trapping or reducing agents, strong Lewis acids, or harsh conditions. Herein, we report a pyridinium salt-catalyzed functionalization of primary, secondary, and tertiary benzylic, allylic, and propargylic alcohols, saccharides, and cyclopropenyl α-carbinols via an unprecedented dearomatization/rearomatization catalytic paradigm. This protocol features mild conditions and an exceptionally broad substrate scope. Molecular dynamics (MD) simulations and DFT calculations support the unprecedented catalytic mode, paving the way for further developments of this concept.