Regioselective Friedel-Crafts Acetylations of 2-Acetylanthracene

The Friedel-Crafts acetylation of 2-acetylanthracene (2-AcAN) with AcCl and AlCl3 in 1,2-C2H4Cl2 gave a mixture of 1,6-diacetylanthracene (1,6-Ac2AN) and 1,7-diacetylanthracene (1,7-Ac2AN), while the Friedel-Crafts acetylation of 2-AcAN in nitrobenzene gave 2,7-diacetylanthracene (2,7-Ac2AN). Both reactions were highly regioselective. B3LYP/6-31G(d) calculations of diacetylanthracenes, their O-protonates and their σ-complexes indicate that 1,6-Ac2AN and 1,7-Ac2AN are the kinetically controlled products, whereas, 2,7-Ac2AN is the thermodynamically controlled product.