Kinetic control wins out over thermodynamic control in Friedel–Crafts acyl rearrangements

1,5-, 1,8- and 9,10-diacetylanthracenes undergo Friedel–Crafts acyl rearrangements in polyphosphoric acid at 130–150 °C to give 3-methylbenz[de]anthracen-1-one via the kinetically-controlled 1,9-diacetylanthracene. The rearrangement mechanism is supported by DFT calculations of diacetylanthracenes, their σ-complexes, O-protonates, and O,O-diprotonates. The importance of kinetic control versus thermodynamic control in Friedel–Crafts acyl rearrangements is highlighted. Certain features of reversibility are also suggested.