Cyclohexanones oxidative ring opening

Greater preparative importance attaches to oxidative ring opening of cycloalkanols and cycloalkanones, which then afford alkanedioic acids containing an unchanged number of carbon atoms. Thus, for instance, adipic acid is obtained in up to 90% yield from cyclohexanol or cyclohexanone by means of about 60% nitric acid containing vanadium and copper salts as catalyst 125... 

Reports of five-membered ring formation involving this mechanism remain unauthenticated. Formation of an oxazolidinone product from Ritter reaction of cyclohexanone and cyclohexanone cyanohydrin has been shown by Ducker to result from an alternative pathway. Although 4-methyl-3-pentenonitrile did undergo intramolecular cyclization, this did not involve pyrrolidone formation. Rather a novel dimeric process took place, leading to formation of a monocyclic (74) and a bi-cyclic (75) product. The latter was readily ring opened to (74) using silver oxide and water (Scheme 37). 

Chromyl chloride, CrOzCE, reacts [64a] with cyclohexane to give a dark precipitate along with chlorocyclohexane and a small amount of cyclohexene. Hydrolysis of the precipitate yields cyclohexanone and chlorocylohexanone. Cyclohexene is readily oxidized by the chromium compound to give mostly ring-opened products with some 2-chlorocylohexanone and cyclohexanone (Scheme VIII. 13). 

Clayden (2002) plan for (-)-kainic acid oxidative degradation of aromatic ring leaving one carbon atom as a carboxylic acid (step 7) cyclohexanone top ring is made in step 3, ring expanded by Baeyer-Villiger oxidation (step 9), and opened np in step 10. 

PCL can be synthesised using two methods, namely by the condensation of 6-hydroxycaproic acid and by the ring-opening polymerisation (ROP) of the cycUc e-caprolactone. This monomer is typically produced by the Baeyer—ViUiger oxidation of cyclohexanone with acetyl hydroxyperoxide (Lecoq et al., 1988). 

The substrates, ( )-E-caprolactones 1, 2 and 3 (Figure 1) were synthesized by Baeyer-Villiger oxidation of the corresponding cyclohexanones and kinetic resolutions were examined using Novozym-43S (immobilized lipase-B from Candida antarctica catalyzed ring-opening of the lactones 1, 2, and 3 with 1.5 molar equivalents of n-butanol (Scheme-1). Authentic samples of the racemic... 

Cyclohexane can be partially oxidized by just attacking one C-C bond to open the ring with functional groups on each end of the six-carbon chain to produce the six-carbon amino acid or adipic acid. Sketch the intermediates to these products starting with cyclohexanone. 

Oxetanes. The reaction of ketones with 3 equiv. of the sodium anion (2) of 1 results in exclusive or predominant formation of the thermodynamically more stable oxetane. For example, axially C—O-bonded oxetanes such as 3 are formed from unhindered cyclohexanones. The reagent 1 can therefore serve as a CH,CH, synthon. Thus reaction of 3 with aqueous HC1 in THF yields a single homoallylic alcohol (4). It (3) is converted into the alcohol 5 in 93% yield on hydroboration followed by oxidation. The oxetane ring is opened by a few other nucleophiles [C6H5SNa, HMPT, (CH3)2CuLi], but is inert to several other nucleophiles, such as QH5SCH2Li and LiCH2C02C(CH3)3. 

Caprolactam can be made in a large number of ways. One method that is used commercially involves oxidation of cyclohexane to cyclohexanone, from which the oxime is made. This oxime reacts by the Beckmann reananganent to give caprolactam. The polymerization of caprolactam is carried out by adding water to open the rings and then removing the water again at elevated temperature, where linear polymer forms. An autoclave or a continuous reactor can be used. 

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