Baeyer-Villiger oxidation regioselective

The action of aqueous potassium hydroxide on chloronitrile 14 in DMSO at 25-30°C accomplishes the hydrolysis of the chloronitrile moiety and furnishes ketone 13 in a yield of 80%. Treatment of a solution of ketone 13 in CH2CI2 with mCPBA and sodium bicarbonate results in a selective Baeyer-Villiger oxidation to give bicyclic lactone 12 in >95% yield. It is noteworthy that the Baeyer-Villiger oxidation is completely regioselective and that the... 

The stereoselective [2+2] cycloaddition between ketenes and enolethers can be used as a key step in the construction of y-butyrolactones (Scheme 14) [45], if the resulting cyclobutanones can subsequently undergo ring enlargement by a regioselective Baeyer-Villiger oxidation. 

Baeyer-Villiger oxidation of the 5a-6-keto steroid 1 with trifluoroperacedc acid is 1000 times faster than oxidation with m-chloroperbenzoic acid and also is more regioselective. This oxidation was used in the last step in a synthesis of brassinolide (2), a natural steroid that promotes plant growth.2... 

The regioselectivity of the migration in Baeyer-Villiger oxidation of ketones is very dependent upon substituents attached to carbon atoms adjacent to the ketone. In a study128 of the MCPBA oxidation of polyhydroxycyclohexanone derivatives, the regioselectivity of the reaction has been carefully identified. This should prove useful to synthetic chemists when planning to use this type of reaction, since cyclitols are important synthons in natural product synthesis. 

A Baeyer-Villiger oxidation has the potential of being asymmetric if a regioselective reaction is conducted on a meso-substrate or if a stereodifferentiated stereogenic center is already present. The oxidation can be chemical or enzymatic.213-215 216 An example of a chemical reagent in a Baeyer-Villiger reaction is provided in the synthesis of fragment A 26 from /f-carvone (27) (Scheme 9.38) as part of a synthesis of Cryptophycin A (28).217... 

The efficiency of this method was demonstrated in a total synthesis of the antibiotic (-r)-tetrahy-drocerulenin 28 (Scheme 8) and (-h)-cerulenin [11]. Irradiation of complex 22 in the presence of the chiral iV-vinyl-oxazolidinone 24, which is easily prepared from the amino carbene complex 23 [12], leads to the cyclobutanone 25 with high diastereoselectivity. Regioselective Baeyer-Villiger oxidation followed by base-induced elimination of the chiral carbamate yields the butenolide 26 in high enantiomeric purity. This is finally converted, using Nozoe s protocol [13], to the target molecule 28 by diastereo-selective epoxidation (- 27) and subsequent aminolysis. 

The regioselective Baeyer-Villiger oxidation of acyclic aliphatic ketones normally results in the insertion of oxygen next to the bulkier alkyl chain. Since methyl is a poor migrating group, a common use of this reaction is to reduce the chain length of methyl ketones 1 two carbons to provide alcohols, after hydrolysis. The ability to synthesize methyl ketones from acids and med l-sutetituted alkenes (equation... 

Because it is often possible to control the stereochemical orientation of substituents on a cyclic array, Baeyer-Villiger cleavages of substituted cyclic ketones have been used extensively in the stereocon-trolled syntheses of substituted carbon chains. An asymmetric synthesis of L-daunosamine intermediate (30) from a noncarbohydrate precursor employed the cyclopentenol (28), prepared in optically pure form (95% ee) from 2-methylcyclopentadiene using asymmetric hydroboration (Scheme 8). Stereoselective epoxidation, conversion to Ae ketone and regioselective Baeyer-Villiger oxidation afforded lactone (29). 

It has been reported that cyclohexanone monooxygenase displays a broad substrate specificity for cyclic ketones38. Moreover, the lactonization of 2-methylcyclohexanone (3), catalyzed by this enzyme, exhibits a regioselectivity comparable with that found for the chemical Baeyer Villiger oxidation oxygen insertion only takes place between the carbonyl group and the substituted carbon center393. 

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