Effective Palladium-Catalyzed Hydroxycarbonylation of Aryl Halides with Substoichiometric Carbon Monoxide

A protocol for the Pd-catalyzed hydroxy­carbonylation of aryl iodides, bromides, and chlorides has been developed using only 1–5 mol % of CO, corresponding to a pCO as low as 0.1 bar. Potassium formate is the only stoichiometric reagent, acting as a mildly basic nucleophile and a reservoir of CO. The substoichiometric CO could be delivered to the reaction from an acyl-Pd­(II) precatalyst, which provides both the CO and an active catalyst, and thereby obviates the need for handling a toxic gas.