- Catalytic Upgrading of Biomass-Derived Methyl Ketones to Liquid Transportation Fuel Precursors by an Organocatalytic Approach
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A highly efficient water-tolerant, solid-base catalyst for the self-condensation of biomass-derived methyl ketones to jet-diesel fuel precursors was developed by grafting site-isolated secondary amines on silica-alumina supports. It is shown that apart from the nature and density of amine groups and the spatial separation of the acidic and basic sites, the acidity of the support material plays a critical role in defining the catalytic activity. It is also found that a combination of weakly acidic silanol/aluminol with secondary amine groups can mimic proline catalysts and are more effective in catalyzing the selective dimerization reaction than the combination of amines with organic acids. In situ FTIR measurements demonstrate that acidic groups activate methyl ketones through their carbonyl groups leading to a favorable C - C bond formation step involving an enamine intermediate. DFT analysis of the reaction pathway confirms that C - C bond formation is the rate-limiting step.
- Sankaranarayanapillai, Shylesh,Sreekumar, Sanil,Gomes, Joseph,Grippo, Adam,Arab, George E.,Head-Gordon, Martin,Toste, F. Dean,Bell, Alexis T.
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- Dehydration-hydration of α-alkynols over zeolite catalyst. Selective synthesis of conjugated enynes and α,β-unsaturated ketones
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α-Alkynols 1 are convened in high yield and selectivity into conjugated enynes 2 or α,β-unsaturated ketones 3 by treatment with acid zeolites. The exclusive production of compounds 2 or 3 depends on the nature of the starting material 1 and experimental conditions.
- Sartori, Giovanni,Pastorio, Andrea,Maggi, Raimondo,Bigi, Franca
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p. 8287 - 8296
(2007/10/03)
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- Catalysis by cobalt compounds of aldol and retroaldol reactions
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Aldol condensation of acetone, butanone, and 2-pentanone, and retroaldol reaction of neat diacetone alcohol and 3-methyl-3-hydroxyheptan-5-one are catalyzed by (Ph3P)3CoCH3 and (Ph3P)3CoSi(CH3)3.The condensations are reversible and the retroaldol reaction is favoured.Several hindered or cyclic ketones, such as higher homologues, 3-pentanone, methyl isopropyl ketone or cyclohexanone do not condense.By comparison, aliphatic aldehydes react fast and irreversibly to yield products comprised of three aldehyde units. (Ph3P)3CoCH3 also catalyzes protium/deuterium scramblingbetween ketones and acetone-d6.This exchange takes place preferably at the C3 carbon whereas condensation takes place at the C1 carbon.The reactions take place at 20 deg C or below, and of the several organometallic compounds tested only the two mentioned above were found to be active.
- Tencer, Y.,Michman, M.,Goldenfeld, I.
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p. 203 - 214
(2007/10/02)
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- REACTIONS OF METHYLTRIS(TRIARYLPHOSPHINE)COBALT III. ALDOL CONDENSATION CATALYSED BY METHYLTRIS(TRIPHENYLPHOSPHINE)COBALT, (Ph3P)3CoCH3
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Methyltris(triphenylphosphine)cobalt catalyses the aldol condensation of acetone and ethyl methyl ketone.From acetone mesityl oxide is obtained in ca. 70percent yield, while from ethyl methyl ketone 3-methyl-2-heptene-5-one and 3-methyl-3-heptene-5-one are formed in equal amounts in a total yield of about 100percent.The latter products are known to be those of base-catalysed aldol condensation.The corresponding aldols are also observed in small quantities.The reactions mostly take place in the absence of solvent.
- Michman, M.,Nussbaum, S.
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p. 111 - 116
(2007/10/02)
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