Lactonization of cyclic ketones

Molybdenum-peroxo compounds have been shown to achieve a variety of selective oxidations they a-hydroxylate enolizable ketones, presumably via epoxidation of the enolate (equation 27) 163 they cause Baeyer-Villiger lactonization of cyclic ketones, probably via the formation of five-membered trioxametallacycles (equation 28) 164 they oxidize alcohols to carbonyl compounds... 

ENANnOSELECnVE LACTONIZATION OF CYCLIC KETONES WITH H2O2 CATALYZED BY COMPLEXES OF PLATINUM(II)... 

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. ... 

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

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. 

Transformation of cyclic ketones into lactones by Baeyer-Villiger oxidation 99EJ0737. 

Transition metal catalysis in Baeyer-Villiger oxidation of cyclic ketones with formation of lactones 98AG(E)1198. 

The reaction of peracids with ketones proceeds relatively slowly but allows for the conversion of ketones to esters in good yield. In particular, the conversion of cyclic ketones to lactones is synthetically useful because only a single product is to be expected. The reaction has been carried out with both percarboxylic acids and Caro s acid (formed by the combination of potassium persulfate with sulfuric acid). Examples of both procedures are given. 

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... 

Organo copper and lithium enolates of cyclic ketones, lactones, and lactams or acyclic ketones are converted with acylimidazoles or imidazole-N-carboxylates into the corresponding / -diketones or / -ketoesters ... 

Oxidation of cyclic ketones by H2O2 in the presence of an acid zeolite was used for the preparation of lactones and u-hydroxycarboxylic acids [124]. Thus, for c-pentanone oxidation in the presence of H-ZSM-5, -valerolactone is obtained with 62.3% selectivity at 40% conversion, whereas 5-hydroxy-pentoic acid is obtained with 34% yield in the presence of Zeolon M. 

The first report of transition-metal peroxides active in the BV oxidation of cyclic ketones was due to Mares and coworkers in 1978 . These authors found that Mo-peroxo complexes, containing picolinato 101 and especially dipicolinato ligands 105, are able to mediate the transformation of some cyclopentanones and cyclohexanones to the corresponding lactones by concentrated H2O2 (equation 70) with yields in the range... 

The photolysis of cyclic ketones, in general, results in homolytic cleavage of the carbon-carbon bond adjacent to the carbonyl function. For details of this process, the reader is referred to the review by Srinivasan.425 Included among the photoproducts are certain oxygen heterocycles, formed by cyclization of reactive intermediates. Thus, cleavage in a cyclic /3-diketone, such as tetramethylcyclobutane-1,3-dione or hexamethylcyclohexane-l,3,5-trione [Eq. (110)] is followed by cyclization on the oxygen atom to form a lactone.426,427 y-Lactone formation is also observed on photolysis of 2,2-diphenylindane-l,3-dione [Eq. (Ill)] in ether, and the process is reversible.428... 

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 ... 

Tin-containing silicalite-2, Sn-Sil-2, has been synthesized [107]. From an 119Sn NMR study, however, it has been suggested that Sn4+ ions are mostly in octahedral coordination. Sn-beta catalyzes the Baeyer-Villiger oxidation of cyclic ketones to lactones without using peracids but using H202 [108]. 

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 . 

One of the most important methods for lactone preparation, and hence of the corresponding hydroxy acids (or halogeno acids, Section 5.14.1 above) is the Baeyer- Villiger rearrangment of cyclic ketones by the action of peracids. A wide variety of peracids have been used in this reaction but currently the reagents of choice are pertrifluoroacetic acid, m-chloroperbenzoic acid, and permaleic acid. The mechanism is formulated below for the conversion of an acyclic ketone into an ester. 

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

Ketones may be oxidized by peroxygen species under a range of conditions. The most common reaction involves the formation of esters, or in the case of cyclic ketones, lactones. This is known as the Baeyer-Villiger reaction.232-235 This reaction can occur under acidic or alkaline conditions (Figure 3.49), first outlined by Criegee.236... 

Treatment of cyclic ketones (Figure 3.51) under acid conditions can give rise to dimeric cycloalkylidene peroxides, which on thermolysis give lactones and CO2 (the Story synthesis).242... 

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