Pentane- 1,5-diol, oxidation

Figure 7. Time-conversion plot for 1,5-pentanediol initiated preparation of polypropylene ether) diol in pentane (propylene oxide/pentane wt ratio = 3) with Zns[Co(CN)6]2 glyme ...

Although the reaction of ketals 16 with an overstoichiometric amount of m-CPBA in dichloromethane under reflux did not proceed at all, the presence of SnCl4 promoted the oxidation and the ketals were smoothly converted into chiral lactones 18 even at low temperatures. The best result was achieved at -100 C with the ketal derived from 3-phenylcyclobutanone (9, R=Ph) and 2,4-pentane-diol. By using 5 equiv of SnC the corresponding lactone was obtained with 89% ee. 

The production of alcohols by the catalytic hydrogenation of carboxylic acids in gas-liquid-particle operation has been described. The process may be based on fixed-bed or on slurry-bed operation. It may be used, for example, for the production of hexane-1,6-diol by the reduction of an aqueous solution of adipic acid, and for the production of a mixture of hexane-1,6-diol, pentane-1,5-diol, and butane-1,4-diol by the reduction of a reaction mixture resulting from cyclohexane oxidation (CIO). 

The reactions of butane-2,3-diol by HCF in alkaline medium using Ru(III) and Ru(VI) compounds as catalysts leads to similar experimental rate equations for both the reactions. The mechanism involves the formation of a catalyst-substrate complex that yields a carbocation for Ru( VI) or a radical for Ru(III) oxidation. The role of HCF is in catalyst regeneration. The rate constants of complex decomposition and catalyst regeneration have been determined.89 A probable mechanism invoving formation of an intermediate complex has been proposed for the iridium(III)-catalysed oxidation of propane- 1,2-diol and of pentane-1,5-diol, butane-2,3-diol, and 2-methylpentane-2,4-diol with HCF.90-92 The Ru(VIII)-catalyzed oxidation some a-hydroxy acids with HCF proceeds with the formation of an intermediate complex between the hydroxy acid and Ru(VIII), which then decomposes in the rate-determining step. HCF regenerates the spent catalyst.93... 

The most convenient column for the separation of fullerenes and their oxides is the column packed by LiChrosorb Diol with eluent containing n-hexane and n-pentane. This... 

Figure 3. Separation of fullerenes and fuUerene oxides on n Bondapak C 18 from i-propanol-n-hexane (20 80) eluent (column 300x4 mm, w = 0.4 ml/min) (a) and on LiChro-sorb Diol from n-hexane - n-pentane (80 20) eluent (column 250x4.6 mm, w = 0.2 ml/min)...

In the case of 1,3-butanediol, the remaining diol had slight optical activity. This showed (S)-configuration at 27% opticd purity. This was determined by comparison of optical rotation with a reference (6). The yeasts could differentiate the (R)- and (S)-alcohol and oxidize the (R)-dcohol predominantly. With 1,4-pentanediol, the yeasts preferred the primary hydroxy group to the secondary one and gave pentane-1,4-olide and its lactol at 6.3% yield. The afforded lactone showed slight optical activity and was the (R)-form at 5% optical purity. This was determined by comparison of optical rotation with a reference (7). This showed that the yeasts preferred (R)-l,4-pentanediol as the substrate. 

Oxidation of Prochiral Diol. The oxidation of prochiral diol 3-methyl-1,5-pentanediol did not give the corresponding -hydroxy aldehyde but gave the corresponding lactol at 22% yield. To determine stereochemistry of the lactol, this was chemically oxidized by Ag20 and afforded 3-(R)-methyl-pentan-l,5-olide at 38% optical purity. (Figure 9). This was determined by comparison of optical rotation with a reference (70). 

Oxidation of 3-substituted pentane-l,5-diols catalysed by horse liver alcohol dehydrogenase furnishes chiral valerolactones. The transformation can be carried out on a synthetically useful scale (2g) in good chemical (75%) and optical (90%) yields, although bulky groups in the 3-position result in a falling-off of the latter (c/. ref. 83). 

Rh(ni)-catalysed oxidation of butane-1,3- and butane-1,4-diol, 2-Me pentane-2,4-and 3-Me pentane-2,4-diol by Ce(IV) in H2SO4 is first order in Ce(IV) at low concentrations, but at high concentration becomes retarded following attainment of a rate maximum. The rates increase with [diol] at low concentrations, becoming independent at higher concentrations. The rate is first order in Rh(IIl), increased by ionic strength but retarded by H+ and Ce + ions. ° The similar Ir(III)-catalysed oxidation of an alcohol and a glycol was catalysed by H+ ions and involved a pre-equilibrium interaction between the catalyst and substrate. ... 

It was known that HLADH oxidizes glycerol into L-glyceraldehyde stereospecifically (Hadorn et al. 1963, Bally and Leuthardt 1970). Since the stereospecific oxidation of a primary diol will afford a lactone, the synthetic utility of this oxidation is quite high. Indeed, six-membered lactones were obtained in high optical yields on oxidations of 3-substituted pentan-1,5-diol as shown in Scheme 33 (Irwin and Jones 1977a). Oxidations of diols mediated by HLADH have been further studied extensively by Jones and his collaborators. A part of a group of results is listed in Table 33 (Irwin and Jones 1977b, Jakovac et al. 1982, Ng et al. 1984, Jones and Francis 1984). 

Pentane-1,5-diol is oxidized to 5-hydroxypentanal (P) by Ce in sulphate media. Two competing effects explain the dependence of the reaction rate on addition of H2SO4 the rate is accelerated by H+ but retarded by HS04 . Inclusion of a dimeric species in the mechanism explains why, when Ce is the rate-limiting reagent, the observed first-order rate constant has a dependence on [Ce vj ... 

Michael addition of the enolate (74) to ( )-ethyl crotonate leads to lactone (75) in an optical yield of 12%. A full report has appeared on an alternative preparation of (75) in quantities of up to 2 g by oxidation of 3-substituted pentane-1,5-diols using horse liver alcohol dehydrogenase. For the 3-methyl derivative (75), the optical yield is 78%, but this figure falls considerably with larger substituents. 

An outer-sphere mechanism is suggested for the oxidation of acetylacetone giving acetic acid by Ce(C104)4 solution. The reaction is first order each in substrate and Ce(IV) and is not catalysed by H+. The oxidations of pentane-l,5-diol, octane-1,8-diol, and fra 5-cyclohexane-l,2-diol by cerium(IV) have been studied in perchloric acid solution intermediate and final products of oxidation were identified and plausible reaction mechanisms were proposed. A mechanism has been proposed for the ruthenium(Vni)-catalysed oxidation of methoxyethanol by Ce(C104)4 in HCIO4 medium, which is zero order in Ce(IV) and H+ and first order each in substrate and Ru(VIII). In oxidations by cerium(IV) perchlorate, fV,fV,-disubstituted anilines gave... 

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