Carboxylic acids, esters Baeyer-Villiger

Peroxyacids are powerful oxidants and so side reactions are to be expected. Ketones are known to undergo Baeyer-Villiger " oxidation to the carboxylic acid ester on treatment with peroxyacids and so these by-products can be observed if oxime hydrolysis occurs during the oxidation. Paquette and co-workers " " observed such a by-product (61) during the oxidation of the dioxime (59) to the dinitro compound (60) with m-CPBA in hot acetonitrile. 

Peroxyphthalic acid Baeyer-Villiger oxidation Carboxylic acid esters from ketones... 

When aldehydes are oxidized with H2SO5 in the presence of alcohols, the esters of the corresponding acids are obtained in very high yields . Mechanistically, it seems plausible that the Baeyer-Villiger reaction occurs first and esterification follows. Thus, the aldehyde is oxidized by H2SO5 to the corresponding carboxylic acid, which is esterified immediately with the alcohol. 

Linkers that enable the preparation of y-lactones by cleavage of hydroxy esters from insoluble supports are discussed in Section 3.5.2. Resin-bound y-lactones have been prepared by Baeyer-Villiger oxidation of cyclobutanones [39], by intramolecular addition of alkyl radicals to oximes [48], by electrophilic addition of resin-bound sele-nenyl cyanide or bromide to 3,y-unsaturated acids (Figure 9.2 [100]), and by palladium-mediated coupling of resin-bound aryl iodides with allenyl carboxylic acids (Entry 10, Table 5.7 [101]). 

Alternative reactions employ coupling reagents such as DCC (Steglich Esterification), preformed esters (transesterification), carboxylic acid chlorides or anhydrides. These reactions avoid the production of water. Another pathway for the production of esters is the formation of a carboxylate anion, which then reacts as a nucleophile with an electrophile (similar reactions can be found here). Esters may also be produced by oxidations, namely by the Baeyer-Villiger oxidation and oxidative esterifications. 

Tetroxans ( dimeric ketone or aldehyde peroxides ) (7) are readily obtainable from carbonyl compounds and Caro s acid or hydrogen peroxide and sulfuric acid by the method described by Baeyer and Villiger.28,20 However, aromatic ketones undergo a Baeyer-Villiger rearrangement under these conditions to form esters of carboxylic acids.30... 

Ketones do not react with most of the reagents used to oxidize aldehydes. However, both aldehydes and ketones can be oxidized by a peroxyacid. Aldehydes are oxidized to carboxylic acids and ketones are oxidized to esters. A peroxyacid (also called a per-carboxylic acid or an acyl hydroperoxide) contains one more oxygen than a carboxylic acid, and it is this oxygen that is inserted between the carbonyl carbon and the H of an aldehyde or the R of a ketone. The reaction is called a Baeyer-Villiger oxidation. 

Primary alcohols are oxidized to carboxylic acids by chromium-containing reagents and to aldehydes by PCC or a Swem oxidation. Secondary alcohols are oxidized to ketones. Tollens reagent can oxidize only aldehydes. A peroxyacid oxidizes an aldehyde to a carboxylic acid, a ketone to an ester (in a Baeyer-Villiger oxidation), and an alkene to an epoxide. Alkenes are oxidized to 1,2-diols by potassium permanganate (KMn04) in a cold basic solution or by osmium tetroxide (OSO4). 

Ba er-Villiger Oxidation Both aldehydes and ketones ate oxidized by peroxy aeids. This reaetion, ealled the Baeyer-Villiger oxidation, is especially nseful with ketones, becanse it converts them to carboxylic esters. For example, treating acetophenone with a peroxy acid converts it to the ester, phenyl acetate. 

The Baeyer-Villiger reaction is a very useful synthesis reaction. An example is the reaction of acetone with peroxyacetic acid to give an ester and a carboxylic acid. This reaction can be generalized as ... 

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