Effect of Microwave Irradiation on the Fries Rearrangement Reactions of Acetyloxy- and Benzoyloxybenzenes

The Fries rearrangement reactions of acetyloxy- and benzoyloxybenzenes were carried out both under microwave irradiation and conventional heating conditions, and the effect of microwave irradiation was examined. Acceleration of the reaction for the acetyloxy derivatives could not be confirmed, but was successfully demonstrated for the benzoyloxy derivatives. On the Fries rearrangement, the Lewis acid coordinates to the ester oxygens, but also coordinates to the aromatic rings. The microwave is efficiently absorbed by such an adduct between the Lewis acid and substrate, resulting in acceleration of the reaction.