Lactones, from cyclic ketones

A brief review of procedures for asymmetric metal-catalyzed Baeyer-Villiger oxidations is given with asymmetric copper-catalyzed synthesis of 3-phenyl-2-oxepanone as representative of the enantioselective synthesis of lactones from cyclic ketones . 

The platinum complexes have also been used in the presence of hydrogen peroxide to prepare cyclic lactones from cyclic ketones (Figure 2.31).91... 

Baeyer-Villiger oxidation. The preparation of lactones from cyclic ketones using MMPP as reagent is mediated by acetonitrile, as well as in the presence of bentonite clay... 

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). 

Lactones from cyclic ketones Ring expansion... 

Peroxybenzoic acid sulfuric acid Lactones from cyclic ketones O... 

Ammonium cerium(IV) sulfate Regiospecific Baeyer-Villiger oxidation Lactones from cyclic ketones... 

Esters can also be formed upon oxidation of ketones with a peroxyacid oxidizing agent (such as mCPBA or CF3CO3H). This Baeyer-Villiger oxidation is especially useful in the preparation of cyclic esters (called lactones) from cyclic ketones. 

Lactones from cyclic ketones— Ring expansion s. 14, 197... 

Ten Brink et al. reported the Baeyer-Villiger oxidation in homogeneous solution catalyzed by diselenide 553 and hydrogen peroxide as oxidant at room tanperature [359]. They achieve faster and excellent conversion and high selectivity onploying only 1 mol% catalyst. They obtained lactones from cyclic ketones, and phenols and acids from aromatic and aliphatic aldehydes. Selected results and the proposed mechanism are shown in Scheme 7.88. 

The chemical properties of cyclic ketones also vary with ring size. Lower members (addition reactions, than corresponding acyclic ketones. The Cg—C12 ketones are unreactive, reflecting the strain and high enol content of medium-sized ring systems. Lactones are prepared from cyclic ketones by the Bayer-Villiger oxidation reaction with peracids. S-Caprolactone is manufactured from cyclohexane by this process ... 

Boric acid derivatives are reported to catalyse lactone formation from cyclic ketones using hydroperoxide oxidants.278... 

Cyclic ethers from cyclic ketones The replacement of the carbonyl group of a cyclic ketone by oxygen can be effected in four steps Baeycr-Villiger oxidation to a lactone, DIBAH reduction to a lactol, (3-scission to an iodoformate, and finally cyclization. 

The reaction of malonate enolates with cyclohexane epoxides leads to mixtures of the two possible lactones (87) and (88)," convertible into the corresponding a-methylene-lactones by now relatively standard procedures. In a similar vein, the bis-spirolactone (90) can be obtained from epoxide (89). Spirolactones can also be prepared from cyclic ketones by condensation with ethyl a-bromomethylacrylate in the presence of zinc, and cyclization of the adduct in cold, dilute acid." ... 

The Baeyer—Villiger oxidation is also widely used for synthesizing lactones (cyclic esters) from cyclic ketones. A common reagent used to carry out the Baeyer—Villiger oxidation is wt fer-chloroperoxybenzoic acid (wCPB A). Certain other peroxycarboxylic acids can be used as well. The following is a mechanism for Baeyer—Villiger oxidation. 

One of the many useful applications of anions of vinyl cyanohydrins, derived from a.jS-unsaturated aldehydes, is in the spiro-lactonization of cyclic ketones for example, cyclohexanone can be converted into (71) in 60% isolated yield. The a-aminonitrile analogues of the cyanohydrins can be used in much the same way. The same spiro-lactonization of ketones can also be carried out using trimethylsilylallylzinc chloride followed by Sharpless epoxidation, hydrolysis, and oxidation, or by using dianions derived from phosphorodiamidates. ... 

The first exploitation of microbial BVase to produce chiral lactones from cyclic racemic bicyclo[2.2.1]hept-2-en-7-ones (Fig. 10) was reported by Ouazzani et al. [17]. A report of preparative scale bioconversion of cyclic ketone was made [26]. The preparative scale bioconversion of using Acinetobacter TD 63 provides lactones in high optical purity [27]. Subsequently [28], whole-cell bioconversions of bicyclic lactones was made, using Acinetobacter sp. NCIB 9871 and Pseudomonas sp. NCIB 9872 to produce file same chiral synthons. In all cases, the racemic ketone was oxidized, and equal amounts of the regioisomeric lactones (—)-(i5, 5/ )-2-oxabicyclo[3.3.0]oct-6-en-3-one and (—)-(iR,55)-3-oxabicyclo[3.3.0]oct-6-en-3-one were produced in high enantiomeric purity. 

For the oxidation of ketones, Baeyer-Villiger oxidation of cyclic ketones with monopersuccinic acid in water gives lactones in good results (Eq. 8.22).47 Peroxy species generated from borax in 30% hydrogen peroxide is effective for the Baeyer-Villiger oxidation of... 

Dianions derived from cyclic a-nitro ketones have been used for the preparation of the natural product phoracanthlide and related macrocyclic lactones (see Scheme 5.2).13 Alkylation of dianion of a-nitro cyclic ketones is followed by radical denitration with Bu3SnH (see Section... 

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