181185-40-0Relevant articles and documents
Asymmetric aldol reactions catalyzed by new spiro diamine derivatives
Jiang, Man,Zhu, Shou-Fei,Yang, Yun,Gong, Liu-Zhu,Zhou, Xiang-Ge,Zhou, Qi-Lin
, p. 384 - 387 (2006)
Two new organocatalysts derived from l-proline and a novel chiral spiro diamine bearing a C2 symmetric backbone, were introduced for an asymmetric aldol reaction in moderate to good asymmetric induction in up to 76% ee and high yields.
An unexpected inversion of enantioselectivity in direct asymmetric aldol reactions on a unique L-proline/γ-Al2O3 catalyst
Zhong, Lin,Xiao, Jianliang,Li, Can
, p. 442 - 445 (2006)
L-proline adsorbed on γ-Al2O3 unexpectedly switches the enantioselectivity of the direct asymmetric aldol reaction of acetone with p-nitrobenzaldehyde from 68% ee (R configuration for free L-proline catalyst) with 80% yield to 21% ee (S configuration) with 78% yield. The inversion of enantioselectivity was also observed in the direct asymmetric aldol reactions of acetone with several other aromatic aldehydes catalyzed by the L-proline adsorbed on γ-Al2O3. This inversion phenomenon is found to be general for different types of amino acids adsorbed on γ-Al2O3. The hydroxyl groups on γ-Al2O3 are found to be involved in the inversion induction of enantioselectivity in these direct asymmetric aldol reactions.
Proline-catalyzed asymmetric aldol reaction in guanidine-derived ionic liquids
Shah, Jabbar,Blumenthal, Haiko,Yacob, Zekarias,Liebscher, Juergen
, p. 1267 - 1270 (2008)
A remarkable improvement of both the chemical yield (from 6% to 82%) and the enantiomeric excess (up to >99%), of (S)-proline catalyzed direct aldol reactions of a wide range of aldehydes with acetone was found when hexasubstituted or pentasubstituted guanidinium salts were added as ionic liquids. Effects of temperature, amount of proline and the type of guandidinium salts on the outcome of the reaction were investigated.
Unusual enantioselectivities in heterogeneous organocatalyzed reactions: Reversal of direction using proline di- versus tri-peptides in the aldol addition
Szollosi, Gy?rgy,Csámpai, Antal,Somlai, Csaba,Fekete, Mónika,Bartók, Mihály
, p. 86 - 92 (2014/01/06)
The heterogeneous asymmetric direct aldol reactions between aldehydes (2-nitrobenzaldehyde, 2-methylpropanal) and ketones (acetone, cyclohexanone) in the presence of polystyrene (PS) resin supported di- and tripeptides were studied under otherwise identic
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.
