FUNCTIONAL SELECTIVITY IN FRIEDEL-CRAFTS ALKYLATIONS WITH POLYFUNCTIONAL REACTANTS OVER ACID ZEOLITES

The selective formation of allyl-substituted aromatics over acid zeoli tes by electrophilic substitution of the aromatics with allyl alcohol is reported. In contrast to the reaction in homogeneous phase with H2S O4, this primary product is stable and almost no consecutive reactions of allyl-substitued aromatics are observed. When aryl chloride (7) is used as alkylating agent, nearly no allyl-substituted aromatic is obt ained. HCI, liberated during reaction easily isomerizes the double bon d, enabling a fast consecutive reaction. This implies that functional selectivity, which is unachievable in homogeneous phase can be easily reached over microporous solid Bronsted acids, provided no homogeneous acid is formed during reaction. The functional selectivity is attribu ted to the suppression of bimolecular side reactions and to the reduce d isomerization rate of the double bond. For the electrophilic aromati c substitution, the turnover number of the acid site is about 120, con firming the true catalytic nature of this reaction. Deactivation of th e catalyst is attributed to the oligomerization of an olefin, made upo n hydride transfer to an allyl cation.