Write and explain the detail mechanism of fries rearrangement
Answers
Answer:
The Reaction
The Fries rearrangement reaction is an organic name reaction which involves the conversion of phenolic esters into hydroxyaryl ketones on heating in the presence of a catalyst. Suitable catalysts for this reaction are Brønsted or Lewis acids such as HF, AlCl3, BF3, TiCl4, or SnCl4. The Fries rearrangement reaction is an ortho, para-selective reaction, and is used in the preparation of acyl phenols.1 This organic reaction has been named after German chemist Karl Theophil Fries.Applications
The Fries rearrangement has found application in the following areas:
The use of an ionic melt [1-butyl-3-methylimidazolium chloroaluminate, ([BMIm]Cl·xAlCl3)] as both solvent and Lewis acid catalyst was investigated. The reaction with phenyl benzoate yields ortho- and para‑hydroxybenzophenone.4
Synthesis of o- and p-hydroxyacetophenones (useful intermediates in the manufacture of pharmaceuticals).5
Total synthesis of α-tocopherol (vitamin E).6
Regioselective synthesis of ortho-acylhydroxy[2.2]paracyclophanes, via TiCl4-catalyzed Fries rearrangement and direct regioselective acylation reaction.7
Synthesis of drug and agrochemical intermediates, thermographic materials, and effective antiviral agents.8
Synthesis of hydroxynaphthyl ketones, via scandium trifluoromethanesulfonate catalyzed Fries rearrangement of acyloxynaphthalenes.9
Photochemical one-pot synthesis of 5-, 6-, and 7-substituted chroman-4-ones from aryl 3-methyl-2-butenoate esters, via a photo-Fries rearrangement and a base-catalyzed intramolecular oxa-Michael addition reaction.10
Scheme of the above syntheses: