“…AlCl 3 ) and that promoted by solid catalysts: (a) the yield of o -hydroxyketone ( 93 ) is greater at high temperatures than that for the reaction at low temperatures, with other conditions being equal; (b) the p / o ratio increases with time of the reaction carried out with a lower amount of Lewis or solid acid, and it remains constant with a higher amount of acid catalyst; (c) solvents of great polarity favor the formation of the para -isomer, as in homogeneous conditions the p / o ratio is determined by the electron densities at the ortho - and para -positions in the phenoxy radical; this is not the controlling factor within zeolites. Mechanistic details merit clarification in order to discriminate between the intra- and intermolecular pathways. − From an experimental point of view, the presence of phenol in the reaction medium is indicative of intermolecular acylation (Scheme a) or deacylation (Scheme b). 23 24 …”
“…AlCl 3 ) and that promoted by solid catalysts: (a) the yield of o -hydroxyketone ( 93 ) is greater at high temperatures than that for the reaction at low temperatures, with other conditions being equal; (b) the p / o ratio increases with time of the reaction carried out with a lower amount of Lewis or solid acid, and it remains constant with a higher amount of acid catalyst; (c) solvents of great polarity favor the formation of the para -isomer, as in homogeneous conditions the p / o ratio is determined by the electron densities at the ortho - and para -positions in the phenoxy radical; this is not the controlling factor within zeolites. Mechanistic details merit clarification in order to discriminate between the intra- and intermolecular pathways. − From an experimental point of view, the presence of phenol in the reaction medium is indicative of intermolecular acylation (Scheme a) or deacylation (Scheme b). 23 24 …”
“…The replacement of these conventional catalysts by heterogeneous reusable acid catalysts is promoting an important effort in heterogeneous catalysis research, mainly in the field of zeolites. Zeolites [4][5][6][7][8][9][10] and other acid heterogeneous catalysts such as the sulfonic resin Nafion [9] have been studied as catalytic systems in the Fries rearrangement of phenyl acetate. Rapid deactivation observed in zeolites, either in gaseous or liquid phase, evidence the need for a greater size pore system.…”
“…The pores of ZSM-5 itself favor the insertions of para substituted benzenes than the ortho ones [18]. Inside the pores, the para products are formed via intermolecular reaction not intra molecular Fries rearrangement [19]. The reactions were indeed designed to occur inside the pores by removing the possible excess of Brosnted acid via drying the ZSM-5.…”
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