Photoredox Catalysis by Phosphorus(V)–Corrole: α-Functionalization of Aldehydes in both Batch and Continuous Flow Conditions

A2B-type P(V)-corroles were synthesized with push–pull meso-aryl substituents to examine their photocatalytic application for C–C bond formation in both batch and flow conditions. The developed protocol requires only 0.25 mol % catalyst to synthesize β-formyl esters in high yields (up to 90%). Remarkably, the reaction time decreased from 5 h to 20 min after moving from a batch to a flow reactor. The P(V)-corroles exhibited excellent fluorescence quantum yields (43–53%), and their singlet-state lifetime was ∼3 ns, making them ideal photocatalysts to take part in the energy transfer process with the substrates. The photophysical and mechanistic insights revealed that P(V)-corrole interacts with substrates via both energy- and single-electron-transfer (SET) pathways. Computational studies of the reaction mechanism suggested that SET occurs via the singlet state of the phosphorus corrole.