Baeyer-Villiger mechanism

The epoxidation of enones by alkaline hydrogen peroxide is well known. Prolonged reaction causes C-C bond fission, probably by a Baeyer-Villiger mechanism. Applied to the 1 o,2a-epoxy-4,6-dien-3-one system (231), this... 

Using Figure 17 15 as a guide write a mechanism for the ] Baeyer-Villiger oxidation of cyclohexyl methyl ketone by peroxybenzoic acid J... 

FIGURE 17 15 Mechanism of the Baeyer-Villiger oxida tion of a ketone... 

Quantum, by contrast, converted an ethylene—carbon monoxide polymer into a polyester-containing terpolymer by treatment with acidic hydrogen peroxide, the Baeyer-Villiger reaction (eq. 11). Depending on the degree of conversion to polyester, the polymer is totally or partially degraded by a biological mechanism. 

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

Compounds known as lactones, which are cyclic esters, are formed on Baeyer—Villiger oxidation of cyclic ketones. Suggest a mechanism for the Baeyer—Villiger oxidation shown. 

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) ... 

Synthesis of all four 8,8a-secobenzophenanthridine alkaloids was carried out chiefly by Baeyer-Villiger oxidation of appropriate benzophen-anthridines (Scheme 32). Thus, arnottianamide (206) was obtained from chelerythrine (210) (172,175), iwamide (207) from N-methyldecarine (211) (168,172), integriamide (208) from avicine (212) (171,172), and isoarnottiamide (209) from nitidine (213) (172,175). The proposed mechanism of this reaction (168,172,175) consists of initial attack of the peroxide ion on the C=N+ double bond followed by rearrangement and hydrolysis. 

To date, reports have involved palladium catalysts for Suzuki and Sono-gashira coupling reactions [63-66], rhodium catalysts for silylations of alcohols by trialkylsilanes [67,68], and tin-, hafnium-, and scandium-based Lewis acid catalysts for Baeyer-Villiger and Diels-Alder reactions [69]. Regardless of exact mechanism, this recovery strategy represents an important direction for future research and applications development. Finally, a particularly elegant protocol where CO2 pressure is used instead of temperature to desorb a fluorous rhodium hydrogenation catalyst from fluorous silica gel deserves emphasis [28]. 

Fig. 23. Mechanism of CHMO-catalyzed Baeyer-Villiger reaction (173,177,178,182).

For oxidation of terminal and internal alkynes to carboxylic acids by RuO / Oxone /Na(HC03)/aq. CHjCN-EtOAc (Table 3.4) a mechanism was proposed in which C3H. CCC3H., is oxidised by RuO to the dione via a Ru(Vl) diester (1), with the resulting dione (2) then undergoing Baeyer-Villiger oxidation by HSOj" to give an acid anhydride (3) which was hydrolysed to the acid (Fig. 1.9 R= C3H3) [377]. 

In 2001, Albrecht Berkessel and Nadine Vogl reported on the Baeyer-Villiger oxidation with hydrogen peroxide in 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) as solvent in the presence of Brpnsted acid catalysts such as para-toluenesulfonic acid (equation 85) . Under these conditions cyclohexanone could be selectively transformed into the corresponding lactone within 40 min at 60 °C with a yield of 92%. Mechanistic investigations of Berkessel and coworkers revealed that this reaction in HFIP proceeds by a new mechanism, via spiro-bisperoxide 234 as intermediate, which then rearranges to form the lactone. The study illustrates the importance of HFIP as solvent for the reaction, which presumably allows the cationic rearrangement of the tetroxane intermediates. 

Density functional theory has been used to model the Baeyer-Villiger reaction mechanism for Ti(IV)-H202 and Sn(IV)-H202 systems. These calculations have shown... 

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. 

The same Pt species that epoxidize double bonds are active in Baeyer-Villiger oxidation of ketones. Strukul has shown that this synthetically interesting process can be carried out also enantioselectively, in the presence of appropriate diphosphine ligands121-123. For this reaction a mechanism has been proposed that involves again a quasi-peroxo metallacycle intermediate, even though in this reaction the metal catalyst plays primarily the role of a Lewis acid while the real oxidant is H2O2 itself (Scheme 9). 

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