Photo fries rearrangement & Barton reaction

Photo fries rearrangement & Barton reaction

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  PRESENTED BY : KESHAVKUMAR SINGH Reg. No.:- Y19266023 Deptt. of Chemistry DHSGU Sagar (M.P.)
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  Photo-Fries Rearrangement Karl TheophilFries was a German chemist. Fries is noted for the discovery of the Fries rearrangement which is an important reaction used in organic synthesis. The Fries rearrangement is a rearrangement reaction of a phenolic ester to a hydroxyl aryl ketone by catalysis of Lewis acids. It involves migration of acyl group of phenol ester to the aryl ring. The reaction is ortho and para selective and one of the two products can be favoured by changing reaction conditions, such as temperature and solvent.
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   Molecular rearrangementalso can be promoted photochemically. Phenolic esters rearrange on irradiation to give ortho and para acyl phenols known as Photo-Fries rearrangement. Photo-Fries Rearrangement Reaction
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  Mechanism of Photo-FriesRearrangement Reaction
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  Example of Photo-FriesRearrangement Reaction
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  Barton Reaction The Bartonreaction, also known as the Barton nitrite ester reaction, is a photochemical reaction that involves the photolysis of an alkyl nitrite to form a δ- nitroso alcohol.
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   The Bartonreaction involves a homolytic RO–NO cleavage, followed by δ-hydrogen abstraction, free radical recombination, and tautomerization to form an oxime. Selectivity for the δ- hydrogen is a result of the conformation of the 6-membered radical intermediate. Often, the site of hydrogen atom abstraction can be easily predicted. This allows the regio- and stereo-selective introduction of functionality into complicated molecules with high yield.
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  Mechanism of BartonReaction
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  Examples of BartonReaction