Proline‐Rich Short Peptides with Photocatalytic Activity for the Nucleophilic Addition of Methanol to Phenylethylenes

Short proline‐rich peptides were synthesized and modified with 1‐(N,N‐dimethylamino)pyrene by copper(I)‐catalyzed cycloaddition. They perform photoredox catalysis of the nucleophilic addition of methanol to 1,1‐diphenylethylene derivatives into products with Markovnikov orientation. The common additive triethylamine is avoided because forward and backward electron transfer is controlled by substrate binding. A free carboxylic function in the substrate allows more precise substrate binding and defines the electron transfer path better than the unspecific exciplex formation with the substrate bearing a carboxylic ester. A proline‐type turn is an advantage for photoredox catalysis, but a proline‐induced helix is not required. This is the first successful example for introducing secondarily structured peptides to photoredox catalysis. The influence of the secondary structure of pyrene‐modified short peptides on photoredox catalysis was studied. One proline is sufficient to yield efficient photoredox catalytic activity.