Aerobic oxygenation of phenylboronic acid promoted by thiol derivatives under gold-free conditions: a warning against gold nanoparticle catalysis

Oxygenation of phenylboronic acid to phenol is promoted by thiol derivatives such as 2-aminothiophenol under aerobic conditions in water without metal catalyst. A plausible mechanism involves autoxidation of thiol to generate hydrogen peroxide in situ, which converts phenylboronic acid into phenol under basic conditions. Since thiols are often utilized as protective ligands for gold nanoparticles (AuNPs), this result is a warning that excess thiols and free thiols liberated from the Au surface could participate in aerobic oxidations catalyzed by thiol-protected AuNPs.