Fries rearrangement mechanism

Views Read Edit View history. In all instances only esters can be used with stable acyl components that can withstand the harsh conditions of the Fries rearrangement. Retrieved from " https: This page was last edited on 20 October , at Fries rearrangement in methane sulfonic acid, an environmental friendly acid A.

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Fries rearrangement in methane sulfonic acid, an environmental friendly acid A. Advanced Organic Chemistry3rd Ed. A low reaction temperature favors para substitution and with high temperatures the ortho product prevails, mechajism can be rationalised as exhibiting classic Thermodynamic versus kinetic reaction control as the ortho product can form a more stable bidentate complex with the Aluminium.

Rearrangement reaction of a phenolic ester to a keto-substituted phenol.

Mangion, Synlett, 23 Rearrangement reactions Name reactions. Tepe, Tetrahedron, 58 In this case, photolysis of the ester groups would lead to leaching of phthalate from the plastic.

In addition to Lewis acid and photo-catalysed Fries rearrangements, there also exists an anionic Fries rearrangement. Only sterically unhindered arenes are suitable substrates, since substituents will interfere with this reaction.

Aromatic Chemistry Oxford Chemistry Primers. Retrieved from " https: The Reaction progress is not dependent on solvent or substrate.

Fries Rearrangement

In this reaction, the aryl ester undergoes ortho-metalation with a strong base, which then rearranges in a nucleophilic attack mechanism. The reaction is ortho and para selective and one of the two products can be favoured by changing mechajism conditions, such as temperature and solvent. By using this site, you agree to the Terms of Use and Privacy Policy.

Zeolites have proven to be unsuitable, since they are deactivated, but strong acids, such as sulfonic acids, provide a reasonable alternative.

In order to avoid the use of these corrosive and environmentally unfriendly catalysts altogether research into alternative heterogeneous catalysts is actively pursued. Gupta, Synthesis, This reaction is also possible with deactivating substituents on the aromatic group.

Fries Rearrangement

Deactivating meta-directing groups on the benzene group will also have an adverse effect as can be expected for a Friedel—Crafts acylation. If the aromatic or the acyl component is heavily substituted then the chemical yield will drop due to steric constraints.

It involves migration of an acyl group of phenol ester to the aryl ring. As an alternative to aluminium chlorideother Lewis acids such as boron trifluoride and bismuth triflate or strong protic acids such as hydrogen fluoride and methanesulfonic acid can also be used. The orientation of the substitution reaction is temperature dependent. From Wikipedia, the free encyclopedia. In the first reaction step a Lewis acid for instance aluminium chloride AlCl 3 co-ordinates to the carbonyl oxygen atom of the acyl group.

Fries rearrangement

The Fries rearrangementnamed for the German chemist Karl Theophil Friesis a rearrangement reaction of a phenolic ester to a hydroxy aryl ketone by catalysis of Lewis acids. This oxygen atom is more electron rich than the phenolic oxygen atom and is the preferred Lewis base.

Cordopatis, Synlett, Because the yields are low this procedure is not used in commercial production. However, reaction with a more distant molecule is also possible:.

The acids are used in excess of the stoichiometric amount, especially the Lewis acids, since they form complexes with both the starting materials and products. Views Read Edit View history.

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