Ortho–Ortho Selective Oxidative Coupling of Phenols by Hydroxo Multicopper(II) Clusters

An ortho–ortho selective aerobic oxidative coupling of unsubstituted, mono- and poly substituted phenols that have been considered beyond the scope of oxidative coupling reactions is reported. The simple conditions involve mixing a phenol with the readily available hydroxo multicopper clusters, particularly the [Cu(tmeda)(μ-OH)]2(ClO4)2 complex, in 1,1,1,3,3,3-hexafluoropropan-2-ol (HFIP). The unprecedented site selectivity is rationalized by the ability of the dicopper complex to bring the two phenolate ligands in proximity to react at the less hindered ortho position. DFT calculations, high-resolution mass spectroscopy, and Infrared photodissociation (IRPD) spectroscopy were applied to reveal key aspects of the reaction.