Aromatic veratrole acylation

The activity of 42%STA/silica catalysts for the acylation of related aromatic reactants with iso-butyric anhydride was investigated. In the presence of anisole and veratrole, 100% anhydride conversion was observed, leading to the expected para-acylation products. No reaction was observed in the presence of chlorobenzene and other deactivated aromatic systems. 

On the other hand, a pure Eley-Rideal mechanism, in which the aromatic compound in the liquid phase reacts with the adsorbed acylating agent was first proposed by Venuto et alP1,22] and more recently by others.[23] However, for acylation reactions of polar substrates (anisole, veratrole), chemisorption of the latter must be taken into account in the kinetic law. A modification, the modified Eley-Rideal mechanism, has been proposed 114,24-26 an adsorbed molecule of acylating agent should react with a nonadsorbed aromatic substrate, within the porous volume of the catalyst. However, the substrate is also competitively adsorbed on the active sites of the zeolite, acting somehow as a poison of the acid sites. That is what we checked through different kinetic studies of various aromatic electrophilic substitution reactions.[24-26]... 

Acylation and alkylation of aromatic compounds. Benzophenones are obtained in good yield when a mixture of a phenolic ether and an alkoxybenzoic acid is treated with PPA prepared by stirring a mixture of 8 parts by weight of P2O5 and 5 parts by volume of 90% orthophosphoric acid (dl. 75) at 85° for 30 min. (Ayers and Denney ). Thus veratrole and vanillic acid afforded4-hydroxy-3,3, 4 -trimethoxybenzophenone. 

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