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

An
oxidative photocatalytic method for phenol–phenol homo-
and cross-coupling is described, and isolated yields of 16–97%
are obtained. Measured oxidation potentials and computed nucleophilicity
parameters support a mechanism of nucleophilic attack of one partner
onto the oxidized neutral radical form of the other partner. Our understanding
of this model permitted the development of cross-coupling reactions
between nucleophilic phenols/arenes and easily oxidized phenols with
high selectivity and efficiency. A highlight of this method is that
one equivalent of each coupling partner is utilized. Building on these
findings, a nonenzymatic, catalytic method for coupling tyrosine was
also developed.