Friedel-Crafts Acylation Of Nitrogen Containing Heterocyclic Aromatic Compounds

Aromatic ketones, especially the aromatic ketones containing heteroatom, are key intermediates of fine chemicals, which have wide applications in the synthesis of pharmaceuticals, pesticides, and dyes. Friedel-Crafts acylation is the main method for the synthesis of them.The Friedel-Crafts acylation of pyrrole with acetic anhydride was carried out over different unmodified zeolites and acid modified beta zeolites. The results showed that phosphoric acid modified zeolite had the highest catalytic activity. The influence of the amount of catalyst, the reaction temperature and the reaction time were investigated and optimized. The conversion of pyrrole was 97.4 % and the selectivities for acetylpyrroles was 93.8 %, while the catalyst amount is 0.4 g, the temperature is 70℃and the reaction time is 5 h. Moreover, the phosphoric acid modified zeolite exhibited good stability in this reaction.Furthermore, Friedel-Crafts acylation of pyrrole with acetic anhydride was studied over different ultrasonic-assisted acid modified zeolites in this paper and the ultrasonic-assisted phosphoric acid modified Hβzeolite is found to have best catalytic performance among all the zeolites studied. The effect of reaction temperature, reaction time, molar ratio and catalyst amount on the acylation of pyrrole were studied in detail to optimize the process parameters. Under the optimized condition, the conversion of acetic anhydride reached 98.8 % and the selectivity for acetylpyrroles was 97.0 %. Moreover, BET, SEM, XPS and TG measurements indicate adsorption the reactants and products on the surface of catalyst result in the deactivation of the catalyst. The service life tests indicate that the regenerated catalyst obtained by a subsequent calcination shows similar activity with the fresh one after six subsequent cycles.In addition, Friedel-Crafts acylation of indole with acetic anhydride was also studied over different zeolites under microwave. Hβzeolite is found to have the best catalytic performance among all the zeolites studied. The effect of reaction temperature, reaction time, molar ratio and catalyst amount on the acylation of indole were investigated and optimized. Under the optimized reaction conditions, the conversion of indole was 86.9 % and the selectivity for 3-acetylindole was 71.5 %.