Friedel–Crafts acylation of anthracene with oxalyl chloride catalyzed by ionic liquid of [bmim]Cl/AlCl3

The acylation reaction of anthracene with oxalyl chloride was investigated in the presence of [bmim]Cl/AlCl3 ([bmin]+ = 1-butyl-3-methylimidazolium cation) ionic liquid. Pure 1,2-aceanthrylenedione was obtained by extraction and recrystallization of the reaction mixture. The structure of 1,2-aceanthrylenedione was identified by GC/MS, FTIR and 1H NMR spectra. The effects of various reaction parameters were investigated. The optimum synthesis conditions of the acylation reaction were given as follows: reacting at 45 °C for 6 h, the molar ratio of AlCl3 in [bmim]Cl/AlCl3 to [bmim]Cl/AlCl3 and [bmim]Cl/AlCl3 to anthracene equal to 0.67 and 2, respectively, and the molar ratio of oxalyl chloride to anthracene equals to 2. At the optimum conditions, the yield of 1,2-aceanthrylenedione is 88.2% and the selectivity is 98.2%. The reusing experiment shows that [bmim]Cl/AlCl3 can be used as both catalyst and solvent, and it is reusable and environmentally friendly for the preparation of 1,2-aceanthryenedione.