Co-catalytic borinate enables air-tolerant copper/oxalamide catalysis for cost-effective hydroxylation of aryl bromides

Copper/oxalamide-catalyzed hydroxylation of aryl bromides has been boosted with respect to air-tolerance and compatibility with cost-effective hydroxides by using co-catalytic dialkylborinates, making the important protocol for phenols more practical without loss of catalytic efficiency. Scope and limitations of the copper/boron co-catalyzed hydroxylation of aryl bromides with potassium hydroxide in air have been demonstrated by more than 20 examples, showing good tolerance to steric and electronic factors albeit low compatibility with base-sensitive functional groups. The boosting effects of co-catalytic dialkylborinates are tentatively attributed to prevention of the catalytically active copper species from deactivation by air and free hydroxide.