43108-68-5Relevant academic research and scientific papers
Tuning the Reactivity of Functionalized Diallylic Alcohols: Br?nsted versus Lewis Acid Catalysis
Lempenauer, Luisa,Du?ach, Elisabet,Lemière, Gilles
, p. 10285 - 10288 (2017/08/07)
The chemodivergent reactivity of bifunctional, enol thioether-containing diallylic alcohols in acidic medium is disclosed, highlighting the difference between strong Lewis acid and mild Br?nsted acid catalysis. In the presence of bismuth(III) triflate, allylic alcohol activation affords diversely substituted cyclopentenones in a Nazarov-type electrocyclization, whereas activation of the thioenol ether by p-toluenesulfonic acid provides an entry to α-sulfenylated β,γ-unsaturated ketones. Both methods represent a facile access to the corresponding products under mild conditions, using inexpensive and non-toxic catalytic systems.
Synthesis of sulphur-modified bifunctional hydrotalcites and study of their surface characteristics by inverse gas chromatography
Ren, Xiaoqian,Hu, Xi,Zhang, Feng,Wang, Junge,Liang, Jinhua,Wu, Wenliang,Jiang, Min,Wang, Jun
, p. 4813 - 4820 (2015/10/05)
In this study, various sulphur-modified hydrotalcite catalysts were prepared, and the influence of calcination temperature on their acid-base properties was investigated. Structural characterization of the catalysts was studied using X-ray powder diffraction, scanning electron microscopy, N2 physisorption, elemental analysis and Fourier transform infrared spectroscopy. The structural characterization indicated that the layer structure of all catalysts was retained but the specific surface areas were enlarged. Inverse gas chromatography was carried out to quantitatively determine the catalysts' acid-base properties by calculating the thermodynamic parameters, including dispersive surface free energy, adsorption free energy, adsorption enthalpy, and acid-base interaction constants. The results showed that the strength and content of acidic and alkaline sites were enhanced with increasing calcination temperature. Moreover, several typical aldol condensation reactions were selected to study the catalytic activity of the developed catalysts. The results showed that the sulphur-modified hydrotalcite catalysts possess high activity and good regenerability for typical aldol condensation reactions.
Reversal of enantioselectivity in aldol reaction: New data on proline/λ-alumina organic-inorganic hybrid catalysts
Sz?ll?si, Gyo?rgy,Fekete, Mónika,Gurka, András A.,Bartók, Mihály
, p. 478 - 486 (2014/06/24)
We report new results on the aldol reactions between aldehydes of three different types (aromatic, aliphatic and cycloaliphatic) and acetone/cycloalkanones as reaction partners, driven by organic-inorganic hybrid catalyst Pro/λ-Al2O3. In contrast to the homogeneous liquidphase reaction, over Pro/λ-Al2O 3reversal of the enantioselection in up to 20-40 % ee depending on the structure of the aldehyde was observed in reactions of acetone. Reversal of the ee in the presence of c-Al2O3cannot be generalized, as it has only been observed for acetone among the ketones studied by us. It was proven using methods of a great variety such as ultrasonic irradiation, reuse measurements on used catalyst and the filtrate of the first reaction, measurements on the L-Pro-L-Pro(OH) dipeptide, studies using mixtures of L-Pro and D-Pro that the organic-inorganic hybrid catalyst Pro/λ-Al 2O3formed in situ is responsible for reversal of the ee. In the reactions of cycloalkanones there is presumably competition between the liquid-phase and the surface reaction over Pro/ c-Al2O 3with preference for the former. Based on these results a surface reaction pathway was proposed. Although, the ees obtained under heterogeneous catalytic conditions are low, further studies may lead to application of this unusual phenomenon for obtaining chiral heterogeneous catalysts suitable for the preparation of the desired enantiomer of a chiral compound using the same chiral source. Springer Science+Business Media New York 2013.
A new robust and efficient ion-tagged proline catalyst carrying an amide spacer for the asymmetric aldol reaction
Montroni, Elisa,Sanap, Shrihari P.,Lombardo, Marco,Quintavalla, Arianna,Trombini, Claudio,Dhavale, Dilip D.
experimental part, p. 3234 - 3240 (2012/01/03)
The synthesis of a new, highly efficient cis-ion-tagged catalyst (8a), possessing an amide linkage between the imidazolium tag and the proline ring, is described. This new bench-stable catalyst has been tested in the classic asymmetric aldol condensation
L-proline/CoCl2-catalyzed highly diastereo- and enantioselective direct aldol reactions
Karmakar, Ananta,Maji, Tapan,Wittmann, Sebastian,Reiser, Oliver
supporting information; experimental part, p. 11024 - 11029 (2011/10/31)
The CoCl2/L-proline (1:2) system was found to be an excellent catalyst for direct aldol reactions. Excellent yields (up to 93 %) and a significant improvement in diastereoselectivity (anti/syn up to 45:1) as well as enantioselectivity (up to mo
Highly diastereo- and enantioselective direct aldol reactions of aldehydes and ketones catalyzed by siloxyproline in the presence of water
Aratake, Seiji,Itoh, Takahiko,Okano, Tsubasa,Nagae, Norio,Sumiya, Tatsunobu,Shoji, Mitsuru,Hayashi, Yujiro
, p. 10246 - 10256 (2008/09/18)
Proline-based organocatalysts have been developed for a highly enantioselective, direct aldol reaction of aldehydes and ketones in the presence of water. While several surfactant-proline combined catalysts have proved effective, proline derivatives with a hydrophobic moiety such as rraw-siloxy-L-proline and cis-siloxy-D-proline, both of which are easily prepared from the same commercially available 4-hydroxy-L-proline. have been found to be the most effective organocatalysts examined in this study, affording the aldol product with excellent diastereo- and enantioselectivities, these two catalysts generating opposite enantiomers. Water affects the selectivity, and poor results are obtained under neat reaction conditions or in dry organic solvents. More than three equivalents of water are required for the best diastereo- and enantioselectivities. while three equivalents is the recommended amount from a synthetic point of view. The reaction proceeds in the organic phase, and also proceeds in the presence of a large amount of water. The large-scale preparation of aldols with the minimal use of an organic solvent, including in the purification step. is described.
Tris(pentafluorophenyl)silyl enol ethers: Synthesis and aldol reactions
Dilman, Alexander D.,Belyakov, Pavel A.,Korlyukov, Alexander A.,Tartakovsky, Vladimir A.
, p. 3741 - 3744 (2007/10/03)
Silyl enol ethers bearing three pentafluorophenyl groups at the silicon atom are described. These compounds undergo uncatalyzed aldol reactions with aliphatic, α,β-unsaturated, and aromatic aldehydes. The observed reactivity is analyzed in terms of the Le
Crossed aldol reaction using cross-linked polymer-bound lithium dialkylamide
Seki, Atsushi,Ishiwata, Fusae,Takizawa, Youichi,Asami, Masatoshi
, p. 5001 - 5011 (2007/10/03)
Cross-linked polymer-bound lithium dialkylamides were employed in crossed aldol reaction of various carbonyl compounds with aldehydes to afford the corresponding β-hydroxycarbonyl compounds. The introduction of spacer chains to the polymer-bound lithium d
Mukaiyama Aldol Reactions of Silyl Enolates Catalyzed by Iodine
Phukan, Prodeep
, p. 1065 - 1070 (2007/10/03)
Iodine catalyzed Mukaiyama aldol reaction of silyl enol ethers and silyl ketene acetal with aldehydes, ketones and acetals in good yield with preferential antiselectivity has been described.
Crossed aldol reaction using polymer-bound lithium amides
Seki, Atsushi,Takizawa, Youichi,Ishiwata, Fusae,Asami, Masatoshi
, p. 342 - 343 (2007/10/03)
Polymer-bound lithium amides were used in an aldol reaction. The introduction of a spacer between the polymer backbone and the reactive site was important to enhance yields of the aldol products. The polymer-bound reagent was repeatedly used in the same r
