A Triple Photoredox/Cobalt/Brønsted Acid Catalysis Enabling Markovnikov Hydroalkoxylation of Unactivated Alkenes

We demonstrate Markovnikov hydroalkoxylation of unactivated alkenes using alcohols through a triple catalysis consisting of photoredox, cobalt, and Brønsted acid catalysts under visible light irradiation. The triple catalysis realizes three key elementary steps in a single catalytic cycle: (1) Co­(III) hydride generation by photochemical reduction of Co­(II) followed by protonation, (2) metal hydride hydrogen atom transfer (MHAT) of alkenes by Co­(III) hydride, and (3) oxidation of the alkyl Co­(III) complex to alkyl Co­(IV). The precise control of protons and electrons by the three catalysts allows the elimination of strong acids and external reductants/oxidants that are required in the conventional methods.