Hydroxylated terphenylphosphine ligands for palladium-catalyzed ortho-selective cross-coupling of dibromophenols, dibromoanilines, and their congeners with Grignard reagents

p-Terphenylphosphines bearing one or two hydroxy groups were used as ligands to palladium in the cross-coupling of dibromophenols, dibromoanilines, and their congeners with Grignard reagents. High ortho-selectivity that cannot be achieved using other phosphine ligands was observed. ortho-Preference was also observed in competitive cross-coupling reactions of two substrates. A significant effect of the concentration of the Grignard reagent on the ortho-selectivity was observed, when the hydroxylated terphenylphosphines were used. Kinetic studies on this effect showed that high concentrations of the Grignard reagent retard the cross-coupling reaction only at the para-position, but not at the ortho-position.