Palladium catalytic system for inhibition of O-arylation type reaction and regioselective direct arylation at C2 of phenols

The palladium-catalysed arylation of free OH phenol derivatives proceeds regioselectively either at C2 or at OH with a variety of electron-deficient aryl bromides or heteroaryl bromides. The nature of the base was found to be crucial to control the regioselectivity of the reaction. In the presence of potassium acetate, the direct arylation at C2 is favoured; whereas, under the same reaction conditions, the use of potassium carbonate gave selectively the O-arylation type products.