Decarbonylative arylation/alkylation of heteroarenes with aldehydes via triplet synergistic catalysis

The development of sustainable synthetic routes from aldehydes to functionalized heteroarenes is an important goal in organic synthesis, owing to the low cost and ready accessibility of aldehydes. However, the high bond dissociation energy (BDE) of the Ar-C(O) bond makes the photocatalytic decarbonylative arylation of heteroarenes a formidable challenge. Herein, we report a novel photocatalytic strategy integrating photoinduced-hydrogen atom transfer (photo-HAT), photoredox, and hydrogen-bonding (HB) organocatalysis for the decarbonylative arylation/alkylation of heteroarenes using aldehydes. This method exhibits broad substrate scope across diverse heteroarenes and aldehydes, delivering products in high yields without metals or strong oxidants. Mechanistic studies show that HB-complexation between aldehydes and TFA is crucial for lowering the decarbonylation barrier. Eosin Y acts as a dual photo-HAT/photoredox catalyst, simplifying the system, while ferrocene promotes oxidative dehydroaromatization.