PALLADIUM(0)-CATALYZED CARBONYLATION OF ARYL AND ALKENYL BORONIC ACIDS WITH CARBON-MONOXIDE LEADING TO ESTERS AND KETONES - TRANSFORMATION OF A C-B BOND TO A C-CO BOND

Arylboronic acids react with carbon monoxide (CO) at atmospheric press ure in methanol at 25 degrees C in the presence of a catalytic amount (1-5 mol%) of tetrakis(triphenylphosphine)palladium(0) to give the cor responding methyl arenecarboxylates and diaryl ketones in moderate yie ld, where the addition of a base, especially sodium acetate, increases the selectivity for the esters. However, when the reactions are carri ed out in aprotic solvents such as tetrahydrofuran (THF), benzene, dic hloromethane and dimethoxyethane, the ketones become the sole carbonyl ation products, THF being the solvent of choice. Alkenylboronic acids react similarly to afford selectively the corresponding methyl alkenec arboxylates in methanol and dialkenyl ketones in THF, respectively. A reaction pathway involving the oxidative addition of a carbon-boron bo nd to palladium(0) is proposed for this catalytic process.