Ketone Baeyer-Villiger reaction

Keywords ketone, Baeyer-Villiger reaction, m-chloroperbenzoic acid, ester... 

The best catalytic performances have been observed for the oxidation of internal olefins, secondary benzylic alcohols and organic sulfur compounds, with >95% H2O2 conversion after 10-50 min of MW irradiation. Oxygen transfer to the electron deficient double bond of chalcone and to cyclic ketones (Baeyer-Villiger reaction) has given 29 and 62% conversion, respectively, after 50 min. 

A variety of esters can be prepared from the corresponding ketones usiag peracids ia a process usually referred to as the Baeyer-Villiger reaction (95) ie, cyclopentanone is converted to 5-valerolactone upon treatment of the ketone with peroxytrifluoroacetic acid ... 

While the oxidation of ketones by peracids (Baeyer-Villiger reaction) has been used in steroids mainly for ring cleavage, it has occasionally been applied to 20-ketopregnanes for conversion to 17-acetoxy- or hydroxyandros-tanes. The synthetic utility of this method is limited since reactive double bonds and other ketones are incompatible with the reagent. 

In the one application reported for the conversion of the 17jff-acetyl side-chain to the 17-ketone, the intermediate oxime was not isolated, but hydrolyzed in situ with acid in an overall yield of about 20 %. In the case of 17jff-acetyl-D-norandrostanes, which are particularly difficult to degrade to D-norandrostanes, the nitrite procedure proved the most convenient method. The yield is 25 %, nowhere near the much higher yield obtained by a Baeyer-Villiger reaction which, however, must be allowed to proceed for one month at 0°. ... 

The Dakin reaction proceeds by a mechanism analogous to that of the Baeyer-Villiger reaction. An aromatic aldehyde or ketone that is activated by a hydroxy group in the ortho or para position, e.g. salicylic aldehyde 12 (2-hydroxybenzaldehyde), reacts with hydroperoxides or alkaline hydrogen peroxide. Upon hydrolysis of the rearrangement product 13 a dihydroxybenzene, e.g. catechol 14, is obtained ... 

In another kind of reaction, an aromatic aldehyde ArCHO or ketone ArCOR is converted to a phenol ArOH on treatment with alkaline H202, but there must be an OH or NH2 group in the ortho or para position. This is called the Dakin reac-The mechanism may be similar to that of the Baeyer-Villiger reaction (18-19) ... 

Another approach is to use the Baeyer-Villiger reaction we have Just carried out to make (34), esterify. and oxidise to the ketone. 

Bolm et al. (130) reported the asymmetric Baeyer-Villiger reaction catalyzed by Cu(II) complexes. Aerobic oxidation of racemic cyclic ketones in the presence of pivalaldehyde effects a kinetic resolution to afford lactones in moderate enan-tioselectivity. Aryloxide oxazolines are the most effective ligands among those examined. Sterically demanding substituents ortho to the phenoxide are necessary for high yields. Several neutral bis(oxazolines) provide poor selectivities and yields in this reaction. Cycloheptanones and cyclohexanones lacking an aryl group on the a carbon do not react under these conditions. 

Baeyer-Villiger reaction Aldehyde, ketones Flavine monooxygenase Esters, lactones... 

Scheme 5.35. Co-catalyzed asymmetric Baeyer-Villiger reaction of ketones.

Oxidoreductases are, after lipases, the second most-used kinds of biocatalysts in organic synthesis. Two main processes have been reported using this type of enzymes-bioreduction of carbonyl groups [39] and biohydroxylation of non-activated substrates [40]. However, in recent few years other processes such as deracemization of amines or alcohols [41] and enzymatic Baeyer-Villiger reactions of ketones and aldehydes [42] are being used with great utility in asymmetric synthesis. 

The remaining chapters deal with a variety of catalysts for effecting oxidation reactions. Chapter 5 describes three simple protocols for the controlled oxidation of primary or secondary alcohols. The importance of stereocontrolled epoxidation and hydroxylation reactions is reflected by the fact that Chapter 6, directed at this field, is one of the most extensive sections of the book. An interesting example of an enantioselective Baeyer-Villiger reaction is featured in Chapter 7, together with an industrially important ketone to enone conversion. Oxidative carbon-carbon... 

The use of a chiral hydroperoxide as oxidant in the asymmetric Baeyer-Villiger reaction was also described by Aoki and Seebach, who tested the asymmetric induction of their TADOOH hydroperoxide in this kind of reaction98. Besides epoxidation and sulfoxidation, for which they found high enantioselectivities with TADOOH (60), this oxidant is also able to induce high asymmetry in Baeyer-Villiger oxidations of racemic cyclobutanone derivatives in the presence of DBU as a base and LiCl as additive (Scheme 174). The yields and ee values (in parentheses) of ketones and lactones are given in Scheme 174 as... 

Baeyer-VUliger Oxidations. The biological equivalent of the Baeyer-Villiger reaction is a useful transformation in providing a mild technique for converting ketones into esters or lactones. 

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