HY zeolite-promoted electrophilic acylation of methoxyarenes with linear acid chlorides

The reaction of ortho-, meta- and para-dimethoxybenzene with linear acyl chlorides under acid zeolite catalysis was examined. Zeolites HY with different SiO2/Al2O3 molar ratio (6, 14 and 390, respectively) were tested and their activity correlated with the acid site distribution (density, nature). It has been postulated that their catalytic performances could be explained in terms of a delicate balance between Bronsted and Lewis acid sites. The chain length of the acyl chloride seems also to play an important role in enhancing the process efficiency. The ketone yield initially increases by increasing the carbon atom number of the chain (from C-2 to C-4) and subsequently falls down (from C-6 to C-10) probably due to the increase of the bulkiness of the reactive system. To confirm the crucial role of the pore dimension of the catalyst even in the liquid-phase system, zeolite HZSM-5, with smaller pore diameter than that of HY (5.1 Angstrom x 5.6 Angstrom versus 7.4 Angstrom x 7.4 Angstrom), was applied in the same reaction, resulting inactive. (C) 2002 Elsevier Science B.V. All rights reserved.