Baeyer-Villiger reaction peroxy acid

Baeyer- Villiger reaction the oxidation of a ketone to an ester or lactone, nsnally by means of a peroxy acid Enone an unsaturated ketone, usually a, f relative to the carbonyl group... 

In a Baeyer-Villiger reaction, ketones (R2C=0) are converted to esters (RCO2R) by using peroxy acids. With an unsymmetrical ketone, two possible esters can be formed, as shown for 3,3-dimethyl-2-butanone as starting material. How could you use spectroscopic techniques—NMR, IR, and MS— to determine which ester (A or B) is formed ... 

Peroxy propionic acid (C2H5CO3H) [340], peroxylauric acid (C11H23CO3H) [174], and other aliphatic peroxy acids [341] are used rarely, and the results do not differ appreciably from those obtained from more common peracids. The same is true of peroxypentafluorobenzoic acid, C FjCOjH, which is obtained from pentafluorobenzaldehyde and ozone and is used for epoxidations the Baeyer-Villiger reaction and the preparation of amine oxides, sulfoxides, and sulfones [342]. 

The oxidation of ketones to esters is known as the Baeyer-Villiger reaction and is effected mainly by hydrogen peroxide and peroxy acids, especially the organic peroxy acids. 

An important addition to the arsenal of oxidants for the Baeyer-Villiger reaction is peroxytrifluoroacetic add [282, 283, 284]. Although this reagent is less easily accessible than peroxyacetic acid and aromatic peroxy acids, it is more reactive. The yields of esters obtained by oxidation of ketones with peroxytrifluoroacetic acid are high enough to justify the use of this oxidant for the quantitative determination of aldehydes and... 

Another dicarboxylic peroxy acid, peroxyphthalic acid, is used for the Baeyer-Villiger reaction of p-diketones and a-keto esters [334]. Besides peroxy acids, ceric ammonium nitrate oxidizes 2-adamantanone to 2-oxa-homoadamantanone in aqueous acetonitrile in 73% yield at 60 °C after 3 h [422]. Tetracyclone (2,3,4,5-tetraphenyl-2,4-cyclopentadien-l-one) is oxidized by ceric ammonium nitrate in aqueous acetonitrile to tetraphenyl-2-pyrone in 77% yield [422]. 

Peroxy adds may epoxidize unsaturated ketones [299, 332], but a concomitant Baeyer-Villiger reaction is possible [254] (equations 389 and 391). Other ways of forming epoxy ketones are reactions with salts of hypochloric acid [691, 704] and with V-bromosuccinimide [746]. Mesityl oxide is converted into its epoxide, as shown in equation 437 [142, 220, 254, 746]. 

By controlling reaction conditions and by proper choice of the peroxy acid, it is often possible to favor the Baeyer-Villiger reaction over epoxidation. An illustrative example of the usefulness of the Baeyer-Villiger reaction is the stereospecific, and regio- and chemoselective conversion of the unsaturated bicyclic ketone shown below to a cyclopentene containing three consecutive stereogenic centers. 

Functional groups that stabilize radicals are expected to increase susceptibility to autoxidation. This is illustrated by two cases that have been relatively well studied. Aldehydes, in which abstraction of the formyl hydrogen is facile, are easily autoxidized. The autoxidation initially forms a peroxycarboxylic acid, but usually the corresponding carboxylic acid is isolated because the peroxy acid oxidizes additional aldehyde in a parallel heterolytic reaction. The final step is an example of the Baeyer-Villiger reaction, which is discussed in Section 12.5.2.1 of Part B. 

The mechanism of the Baeyer-Villiger reaction begins with nucleophilic addition of the peroxy acid to the carbonyl group. 

Baeyer-Villiger reaction (Section 18.12) The reaction of a peroxy acid with a carbonyl group, ultimately giving an ester. 

The Baeyer-Villiger reaction uses a peroxy acid as the reagent ... 

Answer A ketone is being treated with a peroxy acid, so we expect a Baeyer-Villiger reaction to occur. We look closely at our starting ketone, and we see that it is unsynunetrical. So, we must predict where the oxygen atom will insert itself. We look at both sides, and we see that the left side is more substituted. The more substituted R group will migrate faster, and that is where the oxygen atom will be inserted. 

In 1977, Grieco et al. employed benzeneperoxyseleninic acid (495) generated in situ from benzeneseleninic acid (494) and hydrogen peroxide (541). The peroxy acid was employed in overstoichiometric amounts as reagent for the Baeyer-Villiger reaction (Scheme 7.84) [355],... 

The reaction of ketones with peroxy acids is both novel and synthetically useful An oxygen from the peroxy acid is inserted between the carbonyl group and one of the attached car bons of the ketone to give an ester Reactions of this type were first described by Adolf von Baeyer and Victor Vilhger m 1899 and are known as Baeyer—Villiger oxidations... 

Acidic products result from further oxidation of aldehydes (or ketones), again by a radical process. Oxidation of an aldehyde to a carboxylic acid in the presence of air involves a peroxy acid (compare peroxyacetic acid. Section 8.1.2). Finally, a reaction between the peroxy acid and a molecule of aldehyde yields two carboxylic acid molecules this is not a radical reaction, but is an example of a Baeyer-Villiger oxidation. Baeyer-Villiger... 

Mechanism of Baeyer-Villiger Oxidation Both aldehydes and ketones are oxidized by peroxy acids. This reaction, called the Baeyer- Villiger oxidation, is especially useful with ketones. 

In 1899 Baeyer and Villiger observed that peroxy acids convert ketones to esters.179 The reaction is first-order each in ketone and in peroxy acid, and it is general acid catalyzed. Criegee first suggested the mechanism shown in Equation 6.69. The role of the acid catalyst is to protonate the leaving group, thereby facilitating its departure.180... 

RB3LYP calculations indicate that the s-cis conformer of peroxy acids is more stable than the s-trans conformer. Calculations on the reaction of prop-2-enol with some peroxy acids showed that trans-transition states collapse to the epoxide via a 1,2-shift, whereas a 1,4-shift is operable for cis-transition states.195 Quantum mechanical calculations have been performed on the migration step of the Baeyer-Villiger rearrangements of some substituted acetophenones with m-chloroperbenzoic acid (m-CPBA). The energy barriers, charge distributions and frontier molecular orbitals, determined for the aryl migration step, have been used to explain the effects of substituents on the reactivity of the ketones.196... 

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