3102-33-8Relevant articles and documents
Isomerization of 2-Methyl-4,5-dihydrofuran. Studies with a Single-Pulse Shock Tube
Lifshitz, Assa,Laskin, Alexander
, p. 2341 - 2345 (1994)
The isomerization of 2-methyl-4,5-dihydrofuran was studied behind reflected shock waves in a pressurized driver single-pulse shock tube over the temperature range 805-1030 K and densities of approximately ca 3*10-5 mol/cm3.Two isomerization products, acetylcyclopropane and 3-penten-2-one, are obtained in the isomerization.Acetylcyclopropane is formed in an irreversible process from 2-methyl-4,5-dihydrofuran.It further isomerizes, at higher temperatures, to cis- and trans-3-penten-2-one.At high temperatures where the conversion of 2-methyl-4,5-dihydrofuran is high, the main source for 3-penten-2-one is acetylcyclopropane.At lower temperatures 3-penten-2-one is formed mainly by a direct isomerization of 2-methyl-4,5-dihydrofuran.A small concentration of decomposition products, mainly methane and ethane, are also found in shock mixtures of 2-methyl-4,5-dihydrofuran, particularly at high temperatures.The Arrhenius relations for the tree aforementioned processes are as follows: 2-methyl-4,5-dihydrofuran -> acetylcyclopropane, k1=1015.4 exp(-56.8*103/RT) s-1; 2-methyl-4,5-dihydrofuran -> 3-penten 2-one, k2=1015.7 exp(-63.6*103/RT) s-1; acetylcyclopropane -> 3-penten-2-one, k3=1014.4 exp(-58.3*103/RT) s-1, where R is expressed in units of cal/(K mol).
A catalytic asymmetric bioorganic route to enantioenriched tetrahydro- and dihydropyranones
Baker-Glenn, Charles,Hodnett, Neil,Reiter, Maud,Ropp, Sandrine,Ancliff, Rachael,Gouverneur, Veronique
, p. 1481 - 1486 (2007/10/03)
A conceptually novel approach to hetero Diels-Alder adducts of carbonyl compounds is described using as the key steps an antibody-mediated kinetic resolution of hydroxyenones followed by a ring-closure process. Various β-hydroxyenones proved to be very good substrates for antibodies 84G3- and 93F3-catalyzed retro-aldol reactions, allowing the preparation of highly enantiomerically enriched (up to 99% ee) precursors of pyranones. An attractive feature of this methodology is the possibility to convert these acyclicenantioenriched β-hydroxyenones into tetrahydropyranones by a conventional Michael-type addition procedure or into the corresponding dihydropyranones using an alternative palladium-catalyzed oxidative ring closure. For the palladium-mediated cyclization, a biphasic system has been implemented that allows the direct preparation of enantiopure dihydropyranones from the corresponding racemic aldol precursors using a sequential antibody-resolution/palladium-cyclization strategy, without isolation of the intermediate enantioenriched hydroxyenones. This bioorganic route is best applied to the preparation of hetero Diels-Alder adducts otherwise derived from less nucleophilic dienes and unactivated dienophiles.
Oxidation of Diols and Ethers by NaBrO3/NaHSO3 Reagent
Sakaguchi, Satoshi,Kikuchi, Daisuke,Ishii, Yasutaka
, p. 2561 - 2566 (2007/10/03)
NaBrO3 combined with NaHSO3 was found to be an excellent oxidizing reagent of alcohols, diols, and ethers under mild conditions. A variety of aliphatic and cyclic diols were selectively oxidized with satisfactory yields to the corresponding hydroxy ketones and/or diketones, which are difficult to selectively prepare due to a concomitant formation of cleaved products. For example, 2-hydroxycyclohexanone and 1,2-cyclohexanedione were selectively formed by allowing 1,2-cyclohexanediol to react with NaBrO3/NaHSO3 reagent in a selected solvent. On the other hand, an alkyl ether, such as dioctyl ether, reacted with NaBrO3/NaHSO3, in water at room temperature to give octyl octanoate in 82% yield. The same oxidation at higher temperature (60°C) produced the α-brominated ester, octyl 2-bromooctanoate, which is considered to be formed through an alkenyl alkyl ether as the intermediate. The treatment of 1-ethoxy-l-heptene with NaBrO3/NaHSO3 afforded ethyl 2-bromoheptanoate and 2-bromoheptanoic acid as the major products.
