Palladium(0)-catalyzed carbonylation of aryl and alkenyl boronic acids with carbon monoxide leading to esters and ketones. Transformation of a CB bond to a CCO bond

Arylboronic acids react with carbon monoxide (CO) at atmospheric pressure in methanol at 25°C in the presence of a catalytic amount (1-5 mol%) of tetrakis(triphenylphosphine)palladium(0) to give the corresponding methyl arenecarboxylates and diaryl ketones in moderate yield, where the addition of a base, especially sodium acetate, increases the selectivity for the esters. However, when the reactions are carried out in aprotic solvents such as tetrahydrofuran (THF), benzene, dichloromethane and dimethoxyethane, the ketones become the sole carbonylation products, THF being the solvent of choice. Alkenylboronic acids react similarly to afford selectively the corresponding methyl alkenecarboxylates in methanol and dialkenyl ketones in THF, respectively. A reaction pathway involving the oxidative addition of a carbon-boron bond to palladium(0) is proposed for this catalytic process.