Catalytic Intermolecular Ortho-Arylation of Phenols

The use of rhodium catalysts such as [RhCl(PPh3)3] or [[RhCl(COD)]2] with PiPr2(OAr) or P(NMe2)3 co-catalysts allows the ortho-selective intermolecular arylation of phenols. The reaction proceeds via orthometalation of P-OAr groups and then transesterification liberates the product phenol. When 2-substituted phenols are used as substrates, [RhCl(PPh3)3]/iPr2(OAr) mixtures are typically the catalysts of choice, whereas for substrates without 2-substitution [[RhCl(COD)]2]/P(NMe2)3 mixtures tend to give better results.