In memory of Klaus HafnerConventional photoredox catalytic additions of alcohols to olefins require additives, like thiophenol, to promote back electron transfer. The concept of "photozymes" assumes that forward and backward electron transfer steps in a photoredox catalytic cycle are controllable by substrate binding to photocatalytically active peptides. Accordingly, we synthesized a short tripeptide modified with 1,7-dicyano-perylene-3,4 : 9,10-tetracarboxylic acid bisimide as photoredox catalyst. This peptide undergoes an unconventional photoredox catalytic cycle with the radical anion and dianion of the perylene bisimide-peptide as intermediates. The photoredox catalytic reactions with αphenyl styrenes as substrates require remarkably low catalyst loadings (0.5 mol%) and give the methoxylation products in high yields. The concept of "photozymes" for photoredox catalysis has significant potential for other photocatalytic reactions, in particular with respect to enantioselective photocatalysis.
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.
A new method activates CCl 3 F by means of photoredox catalysis and functionalizes alkenes by the CCl 2 F group. N-phenylphenothiazine is used as strongly reducing organophotocatalyst. The photoredox catalytic approach combines the productive disposal of this ozone depleting material and greenhouse gas with the synthesis of potentially useful organic compounds, complements the concept of atom transfer radical addition, and allows for the first time direct synthetic access to the CCl 2 F group as structural motif. The substrate scope is broad and the multifunctionalized class of products allows for a variety of following-up transformations.
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