Oxidation of ketones to esters or lactones

The Baeyer-Villiger oxidation of ketones to esters (or lactones) occurs by the following mechanism. 

Regioselective peroxide oxidation of ketones to esters or lactones with retention of configuration (see 1st edition). 

Polymer encapsulated Bi(OTf)3 catalyst demonstrated also efficiency for the Baeyer-Villiger oxidation [130]. It allowed the oxidation of ketones to esters or lactones using peracids or hydrogen peroxide. In conjunction with m-CPBA, this catalyst displayed comparable activity as shown by Sc(OTf>3 for synthesis of the lactones presented in Equation (8.67). 

Bis(trimethylsilyl) peroxide, (CH3)3SiOOSi(CH3)3, is prepared from trimethylsilyl chloride, l,4-diaza[2,2,2]bicyclooctane, and Dabco s complex with 2 mol of hydrogen peroxide [127]. It is used alone [228] or in the presence of catalysts such as pyridinium dichromate [236] trimethylsilyl trifluoromethanesulfonate, CF3S03Si(CH3)3 [228, 237] or tris-(triphenylphosphine)ruthenium dichloride, [(C6H5)3P]3RuCl2 [236]. This reagent oxidizes primary alcohols to aldehydes (in preference to the oxidation of secondary alcohols to ketones [236]), ketones to esters or lactones Baeyer-Villiger reaction) [238], and nucleoside phosphites to phosphates [228]. All these oxidations require anhydrous conditions. 

Peroxy acids are useful oxidizing agents and are generally analysed on the basis of their ability to oxidize iodide ion to iodine which can be determined titrimetrically or colorimetrically. They also oxidize alkenes to epoxides, ketones to esters or lactones, thioethers to sulphoxides and sulphones, and tertiary amines to amine oxides. 

A PS-peroxyselenic acid (29) was prepared by treatment of PS-mercury(II) chloride (30) with selenium dioxide followed by 30% hydrogen peroxide (Scheme 10). In a triphase system, consi ting of (29) (1.5 mol %), 1.5-1.8 equivalents of 30% aqueous hydrogen peroxide and dichloromethane, alkenes were oxidized to 1,2-diols, and ketones to esters or lactones. The polymeric seleninic acid (31) could be reoxidized to the PS-peroxyseleninic acid (29) and recycled with no apparent loss of activity. 

Acyclic and cyclic ketones may be oxidized to esters or lactones, respectively, by a variety of oxidants including peracids or peroxides associated with suitable catalysts. This reaction is known as Baeyer-Villiger (BV) oxidation and it was originally applied to the oxidation of menthone and tetrahydrocarvone with monopersulfuric acid (equation 69). With the increase of environmental concern, much research has focused on the development of catalytic BV processes based on green and cheap oxidants like hydrogen peroxide and relatively non-toxic metals (Re, Pt, Ti). ... 

Uses, (a) Oxidation of arylamines to nitroso compounds. - (b) Baeyer-Villiger oxidation of ketones to lactones (I) - or esters (3). When an aromatic ring is present (2), cleavage occurs adjacent to this ring. ... 

Another industrially important oxidation reaction, the Baeyer-Villiger oxidation [28] of ketones to esters by 35% aqueous hydrogen peroxide as oxidant, can also be advantageously conducted in a fluorous biphasic medium [29]. When the recyclable fluorous Letvis acidic tin(IV) complex (28) is used as catalyst very high selectivity of conversion of ketones to the corresponding esters or lactones is achieved (Scheme 3.11). 

The Baeyer-Wlliger oxidation of ketones affords esters (from open-chain ketones) and lactones (from cyclic ketones), respectively. It is typically carried out using nucleophilic oxidants, such as peracids or dihydrogen peroxide in the presence of bases (29). Nucleophilic oxidants are required because the first step of the reaction mechanism is the addition of the peroxidic oxidant to the ketone s carbonyl function, affording the so-called Criegee-intermediate (Scheme 10). The subsequent cleavage of the 0 0 bond in the latter, and the concerted shift of yield the ester (lactone) product. In enzymatic Baeyer-Vlliger oxidations, flavin hydroperoxides such as 26 act as the nucleophilic oxidant (30). 

The Baeyer-Villiger Oxidation is the oxidative cleavage of a carbon-carbon bond adjacent to a carbonyl, which converts ketones to esters and cyclic ketones to lactones. The Baeyer-Villiger can be carried out with peracids, such as MCBPA, or with hydrogen peroxide and a Lewis acid. 

Oxidative cleavage of a carbon-carbon double bond produces ketones from tertiary carbons with almost all oxidants. If, however, one or both of the carbons are secondary, either aldehydes or, more generally, carboxylic acids are obtained. In some cases these latter products undergo subsequent reactions to form either esters or lactones. 

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