Baeyer-Villiger Rearrangements

Note meta-Chloroperbenzoic acid (MCPBA) is a broadly used oxidant on the laboratory and industrial scale. It is produced by the oxidation of meta-cYAot-obenzoyl chloride with hydrogen peroxide in the presence of magnesium sulfate in an aqueous solution of sodium hydroxide and dioxane [27]. Since pure MCPBA 

Example 8.8 Consider retrosynthetic analysis and then propose the synthesis of TM 8.8. 

This intermediate is available by an interesting detour, the reaction of cyclohexane epoxide with phenyl-Grignard reagent, followed by oxidation of sec alcohol. The reader should propose a synthetic scheme to TM 8.8 and suggest workable reaction conditions. 

Note There is fascinating chemistry, however, behind cyclohexene, a precursor of cyclohexene epoxide Although a valuable chemical intermediate, it is diflhcult to 

Quite often, rerro-Baeyer-Villiger consideration enables synthetic chemists to propose smprising retrosynthesis of target molecules where this rearrangement is not obvious. Anticipation of Baeyer-Villiger rearrangement of ketone to lactone hidden in the remote retrosynthetic step is elaborate and requires considerable retrosynthetic imagination. The next example serves to support this deliberation. 

Ring contraction reactions of functionalized carbohydrates have become one of very useful tools for methodical syntheses of diversified molecules as reported by Redlich [27]. 

SCHEME 9.9 Samet s synthesis of cyclopropanated lactones via the Baeyer-Villiger rearrangement. 

SCHEME 9.10 Various rearranged products formed as a result of treating dianhydropyra- 

Recent applications of the rearrangement reactions in the synthesis of many functionalized carbohydrates are in accordance with many great developments in organic 

Generally, rearrangement approaches provide mild reaction conditions for the formation of new bonds such as C-C, C-N, C-S, and this type of new bond formation has been exploited in many rearrangements in synthetic carbohydrate chemistry. 

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Baeyer-Villiger rearrangement and hydroxylation of acetophenone catalyzed by TS-I/H2O2 system... 

Oxidation of Ketones to Esters (Baeyer-Villiger rearrangement)... 

These relations are called Baeyer-Villiger rearrangement and in such reactions peroxytrifluoroacetic acid is used as an oxidising agent. 

Ab initio and semiempirical studies on the transition structure of the Baeyer-Villiger rearrangement of acetone with performic acid have been undertaken,510 and a theoretical investigation has been made511 of the mechanism of the Baeyer-Villiger reaction in non-polar solvents. The effect of fluoromethyl groups on the Baeyer-... 

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... 

Enol ethers of 1,2- and 1,3-diketones afford on ozonolysis products that are not in full agreement with the Criegee mechanism, because in some cases products of the Baeyer-Villiger rearrangement are formed. The main product in the ozonolysis of the enol ether 180 is a mixture of spiranic stereoisomers 181 involving a lactone and a 1,2,4-trioxolane ring (Scheme 62) <2004HCA2025>. 

So when the hydroxyketone 49 was needed for a pheromone synthesis, it was made by nucleophilic displacement on the lactone 50 by an organo-lithium compound. This lactone is of the right kind (cf. 45) to be made by a Baeyer-Villiger rearrangement from the cyclohexanone 51 and this can be made by total reduction of the phenol 52 (chapter 36). 

The reason for this becomes plain when you see that the new 1,6-diCO relationship does allow a very interesting reconnection. Adjustment of the oxidation state allows a reconnection to a lactone 61 that should be the product of a Baeyer-Villiger rearrangement on the ketone 62. 

The hydrogenation of 63 occurred quantitatively and with high stereoselectivity (25 1 in favour of 62). The regioselectivity was similarly good in the Baeyer-Villiger rearrangement (12 1) in favour of 61 over the isomeric lactone. Attempts to convert the lactone directly to 60 X = z-Bu gave only low yields. 

Scheme 4 Oxidation followed by Baeyer-Villiger rearrangement and transesterification of nitrated cardanol oil [86]...

Scheme 14 Baeyer-Villiger rearrangement and oxidation of flavones with MT0/H202 [103]...

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