- Cerium oxide as a catalyst for the ketonization of aldehydes: Mechanistic insights and a convenient way to alkanes without the consumption of external hydrogen
-
The ketonization of aldehydes joins two molecules, with n carbon atoms each, to a ketone with 2n - 1 carbon atoms. When employing cerium oxide as a catalyst with nano-sized crystals (15 nm) the ketone can be obtained in almost 80% yield. In addition, other ketones are observed so that the total ketone selectivity reached almost 90%. Water is consumed during the reaction when the aldehyde is oxidized to the corresponding carboxylic acid, which is established as a reaction intermediate, co-producing hydrogen. Consequently, water has to be co-fed in the reaction to enhance the reaction rate and to improve the catalyst stability with time on stream. In contrast to zirconium oxide which possesses catalytic activity for the aldol condensation liberating water, with cerium oxide water is not abundant on the surface and the reaction kinetics show that the reaction rate depends on the concentration of the water in the gas-phase, in addition to the dependence on the gas-phase concentration of the aldehyde. The liberated hydrogen can be consumed in the hydrodeoxygenation of the ketone product. Doing so, when starting from heptanal, a biomass derived aldehyde, an alkane mixture was obtained with almost 90% diesel content. For the whole cascade reaction with five single steps no reagents are necessary and the only by-product is one molecule of innocuous carbon dioxide (related to two molecules of aldehyde). This shows that cerium oxide possesses a big potential to convert biomass derived aldehydes into biofuels in a very sustainable way.
- Orozco, Lina M.,Renz, Michael,Corma, Avelino
-
p. 1555 - 1569
(2017/05/10)
-
- Carbon–Carbon Bond Formation and Hydrogen Production in the Ketonization of Aldehydes
-
Aldehydes possess relatively high chemical energy, which is the driving force for disproportionation reactions such as Cannizzaro and Tishchenko reactions. Generally, this energy is wasted if aldehydes are transformed into carboxylic acids with a sacrificial oxidant. Here, we describe a cascade reaction in which the surplus energy of the transformation is liberated as molecular hydrogen for the oxidation of heptanal to heptanoic acid by water, and the carboxylic acid is transformed into potentially industrially relevant symmetrical ketones by ketonic decarboxylation. The cascade reaction is catalyzed by monoclinic zirconium oxide (m-ZrO2). The reaction mechanism has been studied through cross-coupling experiments between different aldehydes and acids, and the final symmetrical ketones are formed by a reaction pathway that involves the previously formed carboxylic acids. Isotopic studies indicate that the carboxylic acid can be formed by a hydride shift from the adsorbed aldehyde on the metal oxide surface in the absence of noble metals.
- Orozco, Lina M.,Renz, Michael,Corma, Avelino
-
p. 2430 - 2442
(2016/10/24)
-
- An Efficient Direct α-Alkylation of Ketones with Primary Alcohols Catalyzed by [Ir(cod)CI]2/PPh3/KOH System without Solvent
-
α-Alkylation of ketones was successfully achieved by the reaction of ketones with alcohols catalyzed by iridium complexes in the presence of a small amount of base. For example, 2-octanone was allowed to react with butanol under the influence of [Ir(cod)Cl]2/PPh3/KOH to give 6-dodecanone in good yield. The reaction was found to proceed by using a 1:1 mixture of ketone and alcohol without use of any solvent. Copyright
- Taguchi, Kazuhiko,Nakagawa, Hideto,Hirabayashi, Tomotaka,Sakaguchi, Satoshi,Ishii, Yasutaka
-
-
- Synthesis of aliphatic ketones from allylic alcohols through consecutive isomerization and chelation-assisted hydroacylation by a rhodium catalyst
-
Abstract: An allylic alcohol, utilized as a precursor for an aliphatic aldehyde, reacted with olefins to afford aliphatic ketones in the presence of RhCl(PPh3)3, 2-amino-4-picoline, aniline, and benzoic acid through a tandem reaction of an isomerization and a chelation-assisted hydroacylation.
- Lee, Dae-Yon,Moon, Choong Woon,Jun, Chul-Ho
-
p. 3945 - 3948
(2007/10/03)
-
- New coupling reactions of some acyl chlorides with samarium diiodide in the presence of samarium: Carbinols from three acyl units
-
A mixture of samarium(II) iodide and samarium can induce a coupling reaction of three molecules of alkanoyl halide to give trialkylcarbinols of 2-hydroxy-1,3-diones. When aliphatic, unbranched alkanoyl chlorides are used, this new coupling reaction provides trimeric products as the main reaction products. Tetrahydropyran (THP) proved superior as the solvent because no ring-opening and subsequent reaction with the alkanoyl halides was observed under the reaction conditions, unlike when THF was used. Wiley-VCH Verlag GmbH, 2000.
- Clausen, Christian,Weidner, Ingo,Butenschoen, Holger
-
p. 3799 - 3806
(2007/10/03)
-
- The reduction of α-silyloxy ketones using phenyldimethylsilyllithium
-
Phenyldimethylsilyllithium reacts with acyloin silyl ethers RCH(OSiMe3)COR 8 to give regiodefined silyl enol ethers RCH=C(OSiMe2Ph)R 9, and hence by hydrolysis ketones RCH2COR 10. The yields can be high but are usually moderate. The mechanism of this reduction is established to involve a Brook rearrangement (Scheme 6) rather than a Peterson elimination (Scheme 1). Although the mechanism appears to be the same in each case, the stereochemistries of the silyl enol ethers 9 are opposite in sense in the aromatic series (R = Ph, Scheme 7) and the aliphatic series (R = cyclohexyl, Scheme 8), with the major aromatic silyl enol ether being the thermodynamically less stable isomer E-PhCH=C(OSiMe2Ph)Ph E-9aa, and the major aliphatic silyl enol ether being the thermodynamically more stable isomer Z-c-C6H11CH= C(OSiMe2Ph)-c-C6H11 Z-9ba. This is a consequence of anomalous anti-Felkin attack in the aromatic series. The reaction with the silyl ether ButCH(OSiMe3)COPh 13b is normal in giving Z-ButCH= C(OSiMe2Ph)Ph Z-38 (Scheme 11), but reduction of the silyl ether 8a with lithium aluminium hydride is also anti-Felkin giving with high selectivity the meso diol PhCH(OH)CH(OH)Ph 39. The reaction between Phenyldimethylsilyllithium and the acyloin silyl ether 8d (R = But) does not give the ketone ButCH2COBut, but gives instead the anti-Felkin meso diol ButCHOHCHOHBut 40 also with high selectivity (Scheme 12). Silyllithium and some related reagents react with trifluoromethyl ketones 46 and 48 to give α,α-difluoro silyl enol ethers 47 and 49 (Scheme 14).
- Fleming, Ian,Roberts, Richard S.,Smith, Stephen C.
-
p. 1215 - 1228
(2007/10/03)
-