6-Valerolactones

Various cyclic esters have been subjected to hpase-catalyzed ring-opening polymerization. Lipase catalyzed the ring-opening polymerization of 4- to 17-membered non-substituted lactones.In 1993, it was first demonstrated that medium-size lactones, 8-valerolactone (8-VL, six-membered) and e-caprolactone (e-CL, seven-membered), were polymerized by lipases derived from Candida cylindracea, Burkholderia cepacia (lipase BC), Pseudomonas fluorescens (lipase PF), and porcine pancreas (PPL). °... 

Node and coworkers have used this aromatization strategy for the synthesis of (-) aphanor-phine.27 The Diels-Alder reaction of chiral nitroalkene, prepared by the asymmetric nitroolefi-nation reaction of a-methyl-8-valerolactone, with the Danishefsky s diene followed by aromatization is used as a key step for this total synthesis, as shown in Scheme 8.6. 

The cationic ring opening polymerization of e-caprolactone, CL, and 8-valerolactone, VL, was investigated using n-Bu0H/HCl-Et20 as the initiation system [56]. It was observed that narrow molecular weight distribution samples were obtained. These results were combined with those previously... 

H)-furanones undergo efficient cycloadditions as oxa-enones 450). The cycloadducts have been successfully utilized as synthetic precursors for 8-valerolactones 473) (4.62) or for 2-cyclohexenones (4.63)474>. 

Asymmetric intramolecular Reformatsky reactions/ The bromoacetates (1) of (3-hydroxy ketones undergo a Reformatsky-type reaction when treated with Sml2 to give (3-hydroxy-8-valerolactones (2). These products are useful in their own... 

Primary and secondary alcohols are oxidized slowly at low temperatures by benzyltriethylammonium permanganate in dichloromethane primary alcohols produce methylene esters (60-70%), resulting from reaction of the initially formed carboxylate anion with the solvent, with minor amounts of the chloromethyl esters and the carboxylic acids. Secondary alcohols are oxidized (75-95%) to ketones [34] the yields compare favourably with those obtained using potassium permanganate on a solid support. 1,5-Diols are oxidized by potassium permanganate under phase-transfer catalytic conditions to yield 8,8-disubstituted-8-valerolactones [35] (Scheme 10.1). 

The diol (0.18 mol) is added to KMn04 (7.6 g) and TBBA-Cl (0.8 g, 2.4 mmol) in PhH (300 ml) and H20 (300 ml) and the mixture is stirred at room temperature for 12 h. NaHSO, and cone. H2S04 are added to quench the reaction and dissolve the precipitated Mn02. The aqueous phase is separated and extracted with Et20 (3 x 15 ml). The combined organic solutions are dried (Na2S04) and evaporated to yield the 5,5-disubstituted 8-valerolactone... 

Lipases are enzymes of the hydrolase family and, in nature, hydrolyze fatty acid esters in aqueous environment. It is worth recalling that the hydrolysis of esters is a reversible reaction. Chemists thus often use lipases to catalyze the reverse reaction, i.e., the esterification and the ROP of lactones. In 1993, the groups of Kobayashi [91] and Knani [92] reported independently the hpase-catalyzed ROP of sCL and 8-valerolactone. The aliphatic polyesters were functionalized by a carboxylic group at one chain-end and a hydroxyl group at the other chain-end. Accordingly, the polymerization was initiated and terminated by water present in the reaction media. 

Blanquer S, Tailhades J, Darcos V, Amblard M, Martinez J, Nottelet B, Coudane J (2010) Easy synthesis and ring-opening polymerization of 5-Z-Amino-8-valerolactone new degradable amino-functionalized (co)polyesters. J Polym Sci A Polym Chem 48 5891-5898... 

A variety of esters can be prepared from the corresponding ketones using peracids in a process usually referred to as the Baeyer-Villiger reaction (95) ie, cyclopentanone is converted to 8-valerolactone upon treatment of the ketone with peroxytrifluoroacetic acid ... 

P-METHYL-8-VALEROLACTONE (Valeric acid, 5-hydroxy-3-methyl-, 8-lactone)... 

Forty grams (0.215 mole) of the latter were heated under reflux in 100 ml of 2 N sulfuric acid until the evolution of carbon dioxide ceased, giving a solution of a-keto-8-valerolactone. 

Dimethoxyphenylhydrazine hydrochloride (44 g, 0.22 mole) was dissolved in 300 ml of water, treated with a solution of 12.3 g (0.22 mole) of potassium hydroxide in 50 ml of water, and cooled. To this mixture was added the above described solution of a-keto-8-valerolactone, and the pH of the mixture was adjusted to about 2 with 10% sodium hydroxide. The mixture was warmed on a hot plate for five minutes, allowed to cool, extracted with chloroform, and the extracts dried over magnesium sulfate and concentrated to dryness giving 66 g of crude hydrazone. 

Spirocyclic 4-substituted tetrahydropyrans are readily obtained through the Prins reaction involving cyclic ketones, homoallylic alcohols and MeS03H <02H(58)659>. The cationic species generated when alkyne-Co complexes derived from 8-valerolactone are treated with SnCl4 undergo a double cyclisation to yield the oxaspiro[5.5]undecane <02T2755>. 

Valerolacton derivatives, (IV), prepared by Gallop (5) were effective in treating psychiatric disorders, alcoholism, and manic behavior. 

Yamashita, M., Takemoto, Y, lhara, E., and Yasuda, H. (1996) Organolanthanide-initiated living polymerizations of e-caprolactone, 8-valerolactone and f -propiolactone. Macromolecules, 29, 1798-1806. 

Several variations of this reaction are possible. The halo acid is boiled with a solution of sodium in absolute alcohol as in the formation of y-bu-tyrolactone (67%), or the dry sodium salt of a halo acid is heated under vacuum as in the preparation of 8-valerolactone (30%). The corresponding esters are sometimes refluxed with alcoholic potassium hydroxide or decomposed thermally at 15 180° whereby a molecule of an alkyl halide is eliminated. The latter process is valuable in making a-alkyl-y-lac-tones of higher-molecular-weight acids since the y-bromo esters are available by the free-radical addition of a-bromo esters to 1-olefins. 

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