Oxidation, Baeyer-Villiger

The Baeyer-Villiger oxidation of ketones represents a powerful synthetic method that breaks carbon-carbon bonds in an oxygen insertion process to deliver lactones. A recent comprehensive review by ten Brink et describes the different 

Both regioisomeric lactones were obtained in nearly enantiopure form (ee 98 %) and good yield. 

The Baeyer-Villiger oxidation of ketones to esters can be achieved using transition metal catalysts, and an enantioselective variant using chiral nonracemic metal 

Some Baeyer-Villiger oxidations of ketones with iw-chloroperbenzoic acid proceed much faster in the solid state than in solution. For example, when a mixture of 

We have shown that the movement of molecules during the host-guest complex formation process in the solid state is easy. Some host-guest complexes can be formed simply by mixing host and guest compounds in the solid state or keeping a mixture of powdered host and guest at room temperature [2J. Therefore, the ease of oxidation in the solid state is not unexpected. 

2 Enantioselective Reduction of Ketone by NaBH4 and 2BH3-NH2CH2CH2NH2 

Reduction of ketone with NaBH4 also proceeds in the solid state. A mixture of the ketone and a tenfold molar amount of NaBH4 was finely powdered using an agate mortar and pestle and kept in a dry box at room temperature for five days, being stirred once a day. The reaction mixture was extracted with ether, and the dried ether solution was evaporated to give the corresponding alcohol in the yields shown in Table 15-2 [3]. 

The enone moiety of (f )-(-)-l is presumably masked by forming a hydrogen bond with the hydroxyl group of 2a, so that the other carbonyl group is reduced 

When a ketone 1 is treated with hydrogen peroxyde or a peracid, a formal insertion of oxygen can take place to yield a carboxylic ester 2. This process is called the Baeyer-Villiger oxidation  

In a first step the reactivity of the carbonyl group is increased by protonation at the carbonyl oxygen. The peracid then adds to the cationic species 3 leading to the so-called Criegee intermediate 4  

Named Organic Reactions, Second Edition T. Laue and A. Plagens 2005 John Wiley Sons, Ltd ISBNs 0-470-01040-1 (HB) 0-470-01041-X (PB) 

The ease of migration of substituents depends on their ability to stabilize 

The reaction mechanism is supported by findings from experiments with 0-labeled benzophenone 6 after rearrangement, the labeled oxygen is found in the carbonyl group only  

Dioxygen can be used as the oxidant in combination with a sacrificial aldehyde [241], in which case the aldehyde first reacts with dioxygen and the resulting peracid is the oxidant. This is similar to the classical Baeyer-Villiger oxidation. 

A large number of catalysts have been shown to be active in the oxidation of cycloalkanones to lactones using only hydrogen peroxide as the oxidant. Methyl-trioxorhenium (MTO) is moderately active in the oxidation of linear ketones [242] or higher cycloalkanones [243] but it is particularly active in the oxidation of cyclobutanone derivatives (Fig. 4.82), which are oxidized faster with MTO than with other existing methods [244]. 

With 1 mol% MTO cyclobutanones are fully converted within one hour. Another approach consists of the use of a fluorous Sn-catalyst under biphasic conditions [245]. A perfluorinated tin(IV) compound, Sn[NS02C8F17]4, was recently shown to be a highly effective catalyst for BV oxidations of cyclic ketones with 35% hydrogen peroxide in a fluorous biphasic system (Fig. 4.83). The catalyst, which resides in the fluorous phase, could be easily recycled without loss of activity. 

A (lipophilic) quaternary ammonium salt has been shown to catalyze the Beayer-Villiger reaction of aldehydes under halide-and metal-free conditions with aqueous H202 (Fig. 4.85) [249]. 

Surprisingly, both in the oxidation of bicyclo[3.2.0]hept-2-en-6-one and of di-hydrocarvone (not shown) isomeric lactones formed by migration of the secondary carbon, as is usual in Baeyer-Villiger reactions, were not observed. Other 

Free-radical autoxidation of aldehydes with 02 is facile and affords the corresponding peradds, which are used as oxidants for carbonyl compounds. The peracid can transfer an oxygen atom to a substrate such as an olefin or ketone, resulting in the formation of one equivalent of epoxide or ester and add as a co-produd in the absence of metal catalysts [59]. Kaneda and coworkers have developed several HT materials that are active for heterogeneous Baeyer-Villiger reactions with 02/aldehyde [60]. Combination with Lewis addic metals improved the reaction by allowing coordination of the peracid and the intermediate. 

Supported Pt [61] and Ti [62] catalysts have been used in heterogeneous catalyst systems with H202 as an oxidant. However, these catalysts suffered from low TON values and low selectivity. A Sn-substituted beta zeolite was recently applied as a 

The most electron-rich alkyl group (more substituted carbon) migrates first. The general migration order  

Cyclic ketones react through ring expansion to yield lactones (cyclic esters). For example cyclopentanone 7 can be converted to 5-valerolactone 8  

Name Reactions, 4th ed., DOI 10.1007/978-3-642-01053-8 6, Springer-Verlag Berlin Heidelberg 2009 

Curran, T. T. Baeye-Villiger oxidation. In Name Reactions for Functional Group Transformations, Li, J. J., Corey, E. J., eds. John Wiley Sons Hoboken, NJ, 2007, pp 160-182. (Review). 

UHP = Urea-hydrogen peroxide complex Example 2, Chemoselective over lactam  

Name Reactions A Collection of Detailed Mechanisms and Synthetic Applications, DOI 10.1007/978-3-319-03979-4 6, Springer International Publishing Switzerland 2014 

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Baeyer-Villiger Oxidation- oxidation of ketones to esters and lactones via oxygen insertion... 

The reaction of ketones with peroxy acids is both novel and synthetically useful An oxygen from the peroxy acid is inserted between the carbonyl group and one of the attached car bons of the ketone to give an ester Reactions of this type were first described by Adolf von Baeyer and Victor Vilhger m 1899 and are known as Baeyer—Villiger oxidations... 

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

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... 

In a typical Knof procedure, 3jS-hydroxyandrost-5-en-17-one acetate is epoxidized with perbenzoic acid (or m-chloroperbenzoic acid ) to a mixture of 5a,6a- and 5)5,6)5-epoxides (75) in 99 % yield. Subsequent oxidation with aqueous chromium trioxide in methyl ethyl ketone affords the 5a-hydroxy-6-ketone (76) in 89% yield. Baeyer-Villiger oxidation of the hydroxy ketone (76) with perbenzoic acid (or w-chloroperbenzoic acid ) gives keto acid (77) in 96% yield as a complex with benzoic acid. The benzoic acid can be removed by sublimation or, more conveniently, by treating the complex with benzoyl chloride and pyridine to give the easily isolated )5-lactone (70) in 40% yield. As described in section III-A, pyrolysis of j5-lactone (70) affords A -B-norsteroid (71). Knof used this reaction sequence to prepare 3)5-hydroxy-B-norandrost-5-en-17-one acetate, B-noran-... 

Ring contraction by Baeyer-Villiger oxidation of 5-hydroxy-6-keto steroids—cyclization of keto acids 3/S-acetoxy-B-norandrost-5-en-17-one from 3/3-acetoxyandrost-5-en-17-one, 434... 

Baeyer-Villiger oxidation by trifluoraperoxyacetic acid converts a chlo-rofluoroalkyl ketone into an ester 7l ] (equation 63)... 

FIGURE 17.15 Mechanism of the Baeyer-Villiger oxidation of a ketone. 

The product (6-hexanolide) is a cyclic ester, or lactone (Section 19.15). Like the Baeyer-Villiger oxidation, an oxygen atom is inserted between the carbonyl group and a carbon attached to it. But peroxy acids are not involved in any way the oxidation of cyclohexanone is catalyzed by an enzyme called cyclohexanone monooxygenase with the aid of certain coenzymes. 

Section 17.16 The oxidation of ketones with peroxy acids is called the Baeyer-Villiger oxidation and is a useful method for preparing esters. 

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. 

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