Oxidative Photocatalytic Homo- and Cross-Coupling of Phenols: Non-Enzymatic, Catalytic Method for Coupling Tyrosine

The first, oxidative photocatalytic method for phenol-phenol homo-coupling and cross-coupling is described and isolated yields of up to 97% are obtained. Measured oxidation potentials and computed nucleophilicity parameters are consistent with a nucleophilic attack of one partner onto the oxidized radical form of the other partner. Understanding of this model permitted development of cross-coupling reactions between nucleophilic phenols/arenes and easily oxidized phenols in high selectivity and efficiency. A highlight of this method is that one equivalent of each coupling partner is utilized. Building on these findings, the first non-enzymatic, catalytic method for coupling tyrosine was developed.