Benzoylation of 1,2-dimethoxybenzene with benzoic anhydride and substituted benzoyl chlorides over large pore zeolites

Abstract

The benzoylation of 1,2-dimethoxybenzene (veratrole) with benzoic anhydride and substituted benzoyl chlorides has been investigated in the liquid phase (chlorobenzene as solvent) over the H-forms of various zeolites. H-Y and H-BEA have been shown to be efficient catalysts in such a reaction, and led to the selective formation of the corresponding dimethoxybenzophenones. The effect of various experimental parameters on the initial rate of the reaction of veratrole with benzoic anhydride over H-Y zeolite has been studied, leading to propose a suitable mechanism based on the difference of adsorptions of the aromatic substrate and the acylating agent. Moreover, the study of the reaction of veratrole with a series of substituted benzoyl chlorides (4-CH3, 4-OCH3, 4-tert-butyl, 4-Cl, 2-Cl and 2-Br benzoyl chlorides, respectively) over the same H-Y zeolite led to conclude that, due to the high reactivity of the aromatic substrate, the electrophilicity of the acylating agent does not play a relevant role under the given heterogeneous conditions.