C−S Bond Formation Reaction between a Phenolate and Disulfide-Bridged Dicopper(I) Complexes

A novel C−S bond formation reaction took place, when a lithium phenolate derivative was treated with a disulfide-bridged dicopper(I) complex or a bis(μ-thiolato)dicopper(II) complex under very mild conditions. The reaction has been suggested to proceed via a disulfide-bridged (μ-phenoxo)dicopper(I) complex as the common reaction intermediate. Copper(II) complexes of the modified ligands containing a thioether group (products of the C−S bond formation reaction) have been isolated and structurally characterized by X-ray analysis as model compounds of the active site of galactose oxidase. Mechanism of the C−S bond formation reaction is also discussed in relation to the biosynthetic mechanism of the organic cofactor Tyr-Cys of galactose oxidase.