Aldehydes Baeyer-Villiger oxidation

Baeyer-Villiger oxidation (Section 17 16) Oxidation of an aldehyde or more commonly a ketone with a peroxy acid The product of Baeyer-Vilhger oxidation of a ketone is an ester... 

Hassall, C. W., The Baeyer-Villiger oxidation of aldehydes and ketones. Organic Reactions. 9, 73-106, 1957. 

In miscellaneous oxidative processes of indoles, two methods for the preparation of 3-hydroxyindoles have been reported. The first approach involves initial Vilsmeier-Haack reaction of indole-2-carboxylates 176 to afford the corresponding 3-formyl analogs 177. Activation of the aldehyde with p-toluenesulfonic acid (PTSA) and Baeyer-Villiger oxidation with m-chloroperoxybenzoic acid (wi-CPBA) then affords high yields of the 3-hydroxy compounds 178 <00TL8217>... 

Oxidation of aryl aldehydes or aryl ketones to phenols using basic hydrogen peroxide conditions. Cf. Baeyer-Villiger oxidation. 

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... 

SCHEME 159. Selenium-catalyzed Baeyer-Villiger oxidation of aromatic aldehydes and phenol formation via hydrolysis of the intermediary esters... 

Although the parent formaldehyde-derived dioxirane (H2CO2) was the first of this intriguing class of cyclic peroxides to be prepared and spectrally characterized in 1976, the conversion of aldehydes into the corresponding dioxiranes by treatment with Caroate was deemed difficult because of the expectedly facile Baeyer-Villiger oxidation of the aldehydes to their carboxylic acids. Most gratifyingly, however, is that it was recently demonstrated that optically active aldehydes may also serve as promising catalysts for asymmetric epoxidations. For example, ee values up to 94% were obtained with the aldehyde 14 as dioxirane precursor. 

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. 

TABLE 33. Results of the Baeyer-Villiger oxidation of various ketones and aldehydes using different methods... 

Catalysis in reaction systems with undissolved substrates and products is not restricted to biocatalysis. High yields in sobd-state synthesis, sohd-to-sohd reactions, and solvent-free systems have also been reported for aldol condensation, Baeyer-Villiger oxidation, oxidative coupling of naphthols, and condensation of amines and aldehydes [1, 2]. 

C. H. Hassall, The Baeyer-Villiger Oxidation of Aldehydes and Ketones, Organic Reactions 9, 73 (1957). 

Iodine-catalysed hydroperoxidation of cyclic and acyclic ketones with aqueous hydrogen peroxide in acetonitrile is an efficient and eco-friendly method for the synthesis of gem -dihydroperoxides and the reaction is conducted in a neutral medium with a readily available low-cost oxidant and catalyst.218 Aryl benzyl selenoxides, particularly benzyl 3,5-bis(trifluoromethyl)phenyl selenoxide, are excellent catalysts for the epoxidation of alkenes and Baeyer-Villiger oxidation of aldehydes and ketones with hydrogen peroxide.219 Efficient, eco-friendly, and selective oxidation of secondary alcohols is achieved with hydrogen peroxide using aqueous hydrogen bromide as a catalyst. Other peroxides such as i-butyl hydroperoxide (TBHP), sodium... 

Many enzymes are both active and stable in carbon dioxide and have been used to conduct a number of reactions. Several different types of reactions have been examined, including hydrolysis (Lee et al., 1993 Randolph et al., 1985 Zheng and Tsao, 1996), oxidation (Hammond et al., 1985 Randolph et al., 1988), and esterification/transesterification (Kamihira et al., 1987 Nakamura et al., 1986 Rantakyla and Aaltonen, 1994), but there are other types of reactions that would make worthwhile investigations in carbon dioxide. These include preparation of amides, reduction of ketones, preparation of cyanohydrins from aldehydes, aldol reactions, hydroxylation reactions, and Baeyer-Villiger oxidation. 

An important feature of this reaction is that in contrast to most other catalytic asymmetric Mannich reactions, a-unbranched aldehydes are efficient electrophiles in the proline-catalyzed reaction. In addition, with hydroxy acetone as a donor, the corresponding syn-l, 2-aminoalcohols are furnished with high chemo-, regio-, diastereo-, and enantioselectivities. The produced ketones 14 can be further converted to 4-substituted 2-oxazolidinones 17 and /i-aminoalcohol derivatives 18 in a straightforward manner via Baeyer-Villiger oxidation (Scheme 9.4) [5]. 

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