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Fries Rearrangement

Definition: What is Fries Rearrangement?

The Fries rearrangement is an organic reaction used to convert a phenyl ester to a hydroxy aryl ketone using a Lewis acid catalyst and Brønsted acid work-up. In this reaction, an acyl group belonging to phenol ester migrates to the aryl ring either in the ortho or para position, depending on the reaction temperature and solvent. A low reaction temperature favors para substitution, and with high temperatures, the ortho product dominates [1-2].

Fries Rearrangement

The history of this reaction goes back to 1908 when German chemist Karl Theophil Fries reported in a journal.

Examples of Fries Rearrangement

This reaction is used to convert phenyl acetate to ortho- and para- hydroxyphenyl acetate [2].

Fries Rearrangement Phenyl Acetate

Mechanism of Fries Rearrangement

The reaction proceeds through the formation of a carbocation intermediate [2-4].

Fries Rearrangement Mechanism

Applications of Fries Rearrangement

Fries rearrangement has the following applications:

  • Synthesis of o- and p-hydroxy acetophenone, which are useful intermediates in the manufacture of pharmaceuticals
  • Synthesis of drug and agrochemical intermediates, thermographic materials, and active antiviral agents


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  2. Definition, example, and mechanism –
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