Tetrahydrofuran cyclopentanone

Polyesterurethanes, polycarbonate and silicone rubbers have been studied by TG-Tenax-FTIR/MS. The degradation of polyesterurethanes yields C02, water, tetrahydrofurans, cyclopentanone, dicarbonic acid, and aliphatic diols and esters. The thermal decomposition of silicone rubbers leads to the formation of polychlorinated biphenyls which are produced in small amounts and can be observed in the mass spectrometer [86]. 

Jansen and co-workers [86] have evaluated temperature-controlled outgassing processes of plastics and rubbers using both off-line and on-line TD-GC-FTIR-MS. Decomposition of polyesterurethanes by means of TG-Tenax off-line sampling followed by TD-GC-FTIR-MS revealed C02, H20, tetrahydrofurane, cyclopentanone, dicarbonic acid, aliphatic diols and esters [86]. The same authors have also described the detection of polychlorinated biphenyls (PCB) in 2,4-dichlorobenzoylperoxide cured silicone rubbers after outgassing products of a rubber silicone part obtained after desorption for 10 minutes at 200 °C in the thermal desorption cold-trap and subsequent analysis by means of TD-GC-MS. Using a mass range of 290-294 Da the MS can be used as a selective detector for these substances. 

Fig. 7.3. Crystal structures of some lithium etiolates of ketones. (A) Unsolvated hexameric enolate of methyl t-butyl ketone (B) tetrahydrofuran solvate of tetramer of enolate of methyl r-butyl ketone (C) tetrahydrofuran solvate of tetramer of enolate of cyclopentanone (D) dimeric enolate of 3,3-dimethyl-4-(r-butyldimethylsiloxy)-2-pentanone. (Structural diagrams are reproduced from Refs. 66-69.) by permission of the American Chemical Society and Verlag Helvetica Chimica Acta AG.

The reason why the carbonyl group in -santonin remained intact may be that, after the reduction of the less hindered double bond, the ketone was enolized by lithium amide and was thus protected from further reduction. Indeed, treatment of ethyl l-methyl-2-cyclopentanone-l-carboxylate with lithium diisopropylamide in tetrahydrofuran at — 78° enolized the ketone and prevented its reduction with lithium aluminum hydride and with diisobutyl-alane (DIBAL ). Reduction by these two reagents in tetrahydrofuran at — 78° to —40° or —78° to —20°, respectively, afforded keto alcohols from several keto esters in 46-95% yields. Ketones whose enols are unstable failed to give keto alcohols [1092]. 

In agreement with this mechanism, it was found that the epoxide (4RS)-4,4-(epoxy-methano)tricyclo[5.1.0.02,5]octane-e c/o-8-carbaldehyde 2,2-dimethylpropaneT,3-diyl acetal (1) gave 4-oxotricyclo[6.1.0.02,6]nonane- ,/ttreatment with lithium iodide in tetrahydrofuran.71 Several examples employing this oxaspirohexane to cyclopentanone isomerization method are shown (see Table 7).69-80 Lithium bromide in the presence of hexamethylphosphoric triamide was also effective in these transformations.70,74,76 79,80... 

More recently, the formal total syntheses of some bioactive natural products bearing a tetrahydrofurane moiety were achieved by enzymatic Baeyer-Villiger oxidation using cyclopentanone monooxygenases (CPMOs) from Comamonas sp. 

AMI, MP2(fc)/6-31G, and experimental IR spectra were compared by the author for 18 of the 20 compounds in Fig. 6.2 (suitable IRs were not found for HOC1 and CH3SH) and for these 10 cyclopentane, cyclopentene, cyclopentanone, pyrrolidine, pyrrole, butanone, diethyl ether, 1-butanol, 2-butanol, and tetrahydrofuran. On the basis of the relative intensities of the bands, of these 28 compounds only for six, HCN, CH3OH, H2C=CH2, HOF, cyclopentene and cyclopentanone were both the AMI and MP2 spectra similar to the experimental for the others the MP2 IRs were closer to experiment... 

The photo-rearrangement of cyclopentanones to tetrahydrofurans has been applied in the synthesis of the cladiellin skeleton (Equation 105) <2006JOC1172>. 

In contrast, when the X group is oxygen, the reaction appears to follow the cationic alkene cylization-pinacol-like rearrangement pathway. In this case, reaction of an optically pure acyclic oxygen-containing analog of the system in Scheme 71 leads to a product with preservation of optical activity. This reaction protocol, which accomplishes an overall ring expansion with a tetrahydrofuran annulation, has been examined for a-hydroxy-cyclopentanones and -cyclohexanones (Scheme 73 and equations 29-31). ... 

A highly enantioselective and general rhodium(I)-catalysed intramolecular Alder-ene reaction has been developed. a-Methylene-y-butyrolactones, a-methyl-ene-y-butyrolactams, polyfunctional cyclopentanes, cyclopentanones, and functionalized tetrahydrofurans were formed in high yields and excellent enantiomeric... 

FIGURE 8.8 Pyrograms of (a) natural rubber/styrene butadiene blend, (b) polyurethane, and (c) butyl rubbers. 1 = isoprene, 2 = vinylcyclohexene, 3 = styrene, 4 = dipentene, 5 = tetrahydrofuran, 6 = cyclopentanone, 7 = butanediol, 8 = isobutene oligomers. 

Dimethylacetamine, tetrahydrofuran, dichloromethane, methyl ethyl ketone, N,N-dimethylformamide, N-methylpyrrolidone, cyclopentanone, cyclohexanone, dioxane, and chloroform are the most commonly used solvents. Most of these are hazardous but used because they contribute to highly transparent product which is very desirable in medical devices. Transparent materials can only be made from transparent solutions. These solvents can dissolve polymers well and form clear solutions. Ease of solvent removal from the material is very important in formulation design. Obviously, no traces of solvents should remain in the medical devices since even trace amoimts may interfere with the treatment and the patient s health. An inappropriate solvent selection may cause the formation of crust as the solvent escapes. This leads to material discontinuity (e.g., pinholes) which renders the product inferior. This brings a discussion of solvent evaporation, the rheological properties of formulation, and formation of multilayer materials. 

Subsequent treatment of the resulting tetrahydrofuran derivative with Pd in the presence of dppe or PhjP led to isomerization (16 17) the final cyclopentanone product was contaminated by a minor amount of the isomeric cycloheptenone derivative. " Note that the thermal rearrangement of 16 proceeds as a [3,3] shift, affording the cycloheptenone isomer. 

In all of the three polyester systems examined, compositions can be prepared which show solubility in a variety of organic liquids. While most of the solvents are chlorinated hydrocarbons, others such as tetrahydrofuran, n-methyl pyrrolidone, cyclopentanone and dimethyl acetamide are also effective. All of the three polymer systems —... 

Benzyl alcohol at 155.4°C Tetrahydrofuran, acetone-carbon disulfide mixtures, methyl ethyl ketone Toluene, xylene, methylene chloride, ethylene chloride, perchloroethylene-acetone mixtures, 1,2-dichlorobenzene, tetrahydrofurfuryl alcohol, dioxane, acetone-oarbon disulfide mixtures, cyclopentanone, diisopropyl ketone, mesityl oxide, isophorone, dimethyl-formamide, nitrobenzene, hexamethyl-phosphoramide, tricresyl phosphate Aliphatic and aromatic hydrocarbons, vinyl chloride monomer, alcohols, glycols, aniline, acetone, carboxylic acids, acetic anhydride, esters, nitroparaffins, carbon disulfide, nonoxidizing mineral acids, concentrated alkalies... 

A novel 1,3-0 to C-alkyl shift occurs in the presence of bis[l,2-bis(diphenylphosphino)ethane]palladium such that a number of alkylidene-tetrahydrofurans undergo rearrangement to cyclopentanones (Scheme 7). The mechanism of the reaction is thought to involve oxidative addition of the allyl ether to Pd to form a zwitterionic intermediate, which then collapses by C-alkylation to the cyclic product. Related rearrangement reactions have also been reported. ... 

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