Dual Nickel/Photoredox-Catalyzed Aryl Etherification Enabled by an Oxidative Near-Infrared-to-Blue Triplet–Triplet Annihilation Upconversion System Leveraging Spin-Forbidden Excitation

Herein we describe a near-infrared-to-blue triplet–triplet annihilation upconversion system that produces a highly oxidizing excited state. The spin-forbidden excitation of the osmium sensitizer and thermally assisted triplet energy transfer to the anthracene annihilator enable an anti-Stokes shift of 1.25 V. This system is then applied to the dual nickel/photoredox-catalyzed cross-coupling of aryl halides and alcohols. Finally, we implicate upconversion as the promoter for reductive elimination of a nickel(II) aryl alkoxide complex.