Baeyer Villiger caprolactone

Alphand, V., Furstoss, R., Pedragosa-Moreau, S., Roberts, S.M. and Willetts, A.J., Comparison of microbiologically and enzymatically mediated Baeyer-Villiger oxidations synthesis of optically active caprolactones. J. Chem. Soc. Perkin Trans. 1, 1996, 1867. 

We were interested in applications of the high level of stereocontrol associated with the asymmetric Birch reduction-alkylation to problems in acyclic and heterocyclic synthesis. The pivotal disconnection of the six-membered ring is accomplished by utilization of the Baeyer-Villiger oxidation (Scheme 7). Treatment of cyclohexanones 25a and 25b with MCPBA gave caprolactone amides 26a and 26b with complete regiocon-trol. Acid-catalyzed transacylation gave the butyrolactone carboxylic acid 27 from 26a and the bis-lactone 28 from 26b cyclohexanones 31a and 31b afforded the diastereomeric lactones 29 and 30. ... 

The Baeyer-Villiger oxidation of cyclohexanone to form e-caprolactone (78) using peroxybenzoic acid, as indicated in equation (40), may be considered as a further type of intramolecular displacement reaction of value in seven-membered ring synthesis (49JA2571). 

One of the achievements in Baeyer-Villiger oxidation is aerobic catalytic rearrangement of cyclic ketones, for example, / -butylcyclohexanone, in the presence of Ru02 or Mn02 (0.05 equiv) and benzaldehyde (3 equiv) at room temperature (Equation 32), giving the respective e-caprolactones in yields up to 95%, the reaction being accelerated in the presence of lithium perchlorate <1994SL1037>. 

Illustration of the simultaneous determination of intermolecular and intramolecular 13C and 2H KIEs at natural abundance are studies of the Baeyer-Villiger (B-V) oxidation of cyclohexanone to s-caprolactone.48... 

The Baeyer-Villiger oxidation of cyclohexanone to e-caprolactone using H202 in (CF3)2CHOH proceeds via 7,8,15,16-tetraoxadispiro[5.2.5.2]hexadecane 32. The tetraoxane can be isolated and rearranges to the lactone on treatment with catalytic amounts of 4-TsOH <02 AG(E)4481>. 

Percarboxylic acids have been used widely in Baeyer-Villiger oxidation. Peracetic acid is one of the most commonly used peracids distilled peracetic acid is employed commercially by Solvay Interox for the production of e-caprolactone.246 The use of distilled peracetic acid is essential, as it contains no strong protic acids which can catalyse polymerization of the resulting lactone and cause other side reactions. Figure 3.53 illustrates the use of pre-formed peracetic acid for the Baeyer-Villiger oxidation of ketones.247,248... 

The Baeyer-Villiger reaction is also effected by biochemical oxidation using the enzyme cyclohexanone oxygenase from Acinetobacter strain NCIB 9871. Cyclohexanone is thus converted into e-caprolactone [1043], and phenylacetone (l-phenyl-2-propanone) is transformed into benzyl acetate. The formation of benzyl acetate from phenylacetone involves the same migration as that in oxidation with peroxytrifluoroacetic acid (equation 387) [1034]. More examples of biochemical Baeyer-Villiger reactions occur in diketones and steroids see equation 397). 

Under the name Oxone an oxidation agent has been introduced, consisting of KHSO4-K2SO4-2KHSO5. Solid Oxone converts methylenic functions under anhydrous, biphasic conditions to carbonyl compounds under the catalytic influence of ligand-modified Mn porphyrins and phase-transfer catalysts (e. g., acetophenone is obtained from ethylbenzene). In the case of cyelohexane, e-caprolactone results as well as cyclohexanol and -one ([219 b, 241] cf. also Baeyer-Villiger oxidation). Biphasic oxidations with methyltrioxorhenium (e. g., to epoxides) are reviewed in Section 3.3.13 [244 i]. 

Oxepan-2-one 18 (hexano-6-lactone, f caprolactone) is of commercial importance for the production of the polyester poly-s -caprolactone. It is obtained by a Baeyer-Villiger oxidation of cyclohexanone with peroxy acids ... 

The Ti-silicalite catalysed Baeyer-Villiger oxidation of cyclohexanone by H2O2 in aqueous solution promotes a high concentration of OH radicals, which accelerate the reaction and the consecutive formation of adipic acid (and of lighter diacids as well) as the kinetically preferred product. In the absence of the catalyst, the primary reaction product is e-caprolactone, which quickly undergoes consecutive transformations to form adipic acid even when a stoichiometric amount of the oxidant is used, since it is more reactive than cyclohexanone. The choice of solvent, which could act as a radical scavenger, also allows control over the reaction rates. ° ... 

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... 

S)-4-Ethyl-e caprolactone using an enzymatic Baeyer-Villiger oxidation. The general procedure described above was also used to oxidize 4-ethylcyclohexanone (10 mmoles, 1.41 mL). In this case, an equimolar quantity of P-cyclodextrin (10 mmoles, 11.33 g) was included in the YP-Gal medium to solubilize the hydrophobic ketone. Extractive workup afforded 1.76 g of crude lactone as an orange oil. 

Selected catalysts were then evaluated in the Baeyer-Villiger oxidation (57) of cyclohexanone to caprolactone with air and a sacrificial aldehyde (52). The results are summarised in Figure 4. Catalyst stability was measured by carrying out atomic absorption studies on the supernatant solution after reaction. Catalytic activity varied dramatically, but high yields of caprolactone were obtained with the best catalysts. 

Poly( caprolactone) [90,9195,97,98,103,106-1 lOJ 13J25-131] Poly(e-caprolactone) (PCL) is another biodegradable polyester that has been extensively investigated as a potential biomaterial. PCL was first synthesized by Carothers by ringopening polymerization of e-caprolactone. e-caprolactone, a cyclic ester, which can be prepared by the Baeyer-Villiger reaction for the oxidation of cyclic ketones and... 

In this case the concept was exemplified with a Baeyer-Villiger monooxygenase and an alcohol dehydrogenase for the synthesis of e-caprolactone from cyclohexanone and the so-called "double-smart cosubstrate" 1,6-hexanediol [55]. 

---