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Migration from C to O or

Problem 2.16. The Baeyer-Villiger reaction can also be carried out under basic conditions. Draw a reasonable mechanism. [Pg.91]

The Hofmann rearrangement can also be used to convert a carboxylic acid derivative to an isocyanate. A carboxamide is treated with Br2 and aqueous base to give an isocyanate, which is usually hydrolyzed under the reaction conditions to give an amine with one fewer C atom than the starting material. The reaction proceeds by deprotonation of the amide and /V-bromination, then a second deprotonation and rearrangement. The amide N is more reactive than the amide O in the bromination step because N is deprotonated under the reaction conditions. [Pg.91]

Ketones react with peracids (RCO3H) to give esters in the Baeyer-Villiger oxidation. The peracid is usually m-chloroperbenzoic acid (mCPBA) peracetic acid and trifluoroperacetic acid are also commonly used. Peracids have an O—OH group attached to the carbonyl C. They are no more acidic than alcohols, because deprotonation of the terminal O does not give a stabilized anion, but they are usually contaminated with some of the corresponding acid. The Baeyer-Villiger reaction is thus usually conducted under mildly acidic conditions. Protonation of the ketone O occms first to make the carbonyl C even more electrophilic than it [Pg.84]


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Migration from C to

O-migration

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