Reversal of Enantioselectivity in Aldol Reaction: New Data on Proline/γ-Alumina Organic–Inorganic Hybrid Catalysts

Szőllősi, György; Fekete, Mónika; Gurka, András A.; Bartók, Mihály

doi:10.1007/s10562-013-1177-1

Cited by 13 publications

(13 citation statements)

References 26 publications

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“…During our study we have obtained increased ee using several oxide additives (γ‐Al 2 O 3 , Mg−Al LDH, Mont, Ben H). Thus, the adsorption mode of l ‐Pro on the surface may be assumed to be similar with that suggested in previous studies employing l ‐Pro‐γ‐Al 2 O 3 or l ‐Pro‐Mg−Al LDH catalysts in asymmetric aldol or Michael additions, respectively . However, on cation‐exchanger layered material, such as Lap RD, the formation of the corresponding salt‐like adsorbed amino acid is also possible by interaction with the charge compensating cation, as shown in Scheme (A).…”

Section: Resultssupporting

confidence: 60%

“…Our initial investigations were inspired by the effect of the γ‐Al 2 O 3 additive in the enantioselective aldol addition catalyzed by l ‐proline ( l ‐Pro), which was attributed to in situ formation of l ‐Pro‐γ‐Al 2 O 3 hybrid material ,. Thus, we started to study the effect of various inorganic oxide additives in the enantioselective addition of butanal ( 2 a ) to trans ‐β‐nitrostyrene ( 1 a ).…”

Section: Resultsmentioning

confidence: 99%

“…The present study on using inorganic oxide additives in the asymmetric Michael addition of aldehydes to trans ‐β‐nitrostyrene derivatives catalyzed by l ‐Pro showed a surprising increase in the enantioselectivity in presence Lap RD. Such improvement in the ee on a solid surface is without precedent in asymmetric organocatalysis, although examples of peculiar behaviour of surface‐adsorbed chiral organocatalysts has been observed previously …”

Section: Resultsmentioning

confidence: 99%

“…Natural amino acids are cheap, readily available chiral organocatalysts. However, only few catalytic systems are known in which these were immobilized on supports by simple adsorption or hydrogen bonding and provided improved activity, stereoselectivity or in few cases altered stereochemical course in asymmetric reactions . From practical point of view it is important that anchoring of the organocatalyst on supports by simple adsorption may be carried out in situ, without pre‐preparation of the solid catalyst.…”

Section: Introductionmentioning

confidence: 99%

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Surface‐Improved Asymmetric Michael Addition Catalyzed by Amino Acids Adsorbed on Laponite

et al. 2018

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An unprecedented enantioselectivity increase was observed in the presence of inorganic oxides in the asymmetric Michael addition of aldehydes to trans-b-nitrostyrene derivatives catalyzed by amino acids. The best results were reached in the l-proline catalyzed addition of linear aldehydes using laponite RD as additive, approaching those obtained using synthetic chiral organocatalysts. In our study we have shown that the asymmetric Michael addition is catalyzed by the organic-inorganic hybrid material formed in situ by adsorption of the amino acid on the solid surface. The chiral solid catalyst could be pre-prepared and recycled several times with maintained stereoselectivities, showing a slow decrease in the activity, which could be restored by adding proline during reuse. Characterization of the chiral hybrid material by FT-IR spectroscopy and XRD measurements indicated anchoring of the proline on the surface of the laponite particles. Effect of the chiral organocatalyst structure was used to evidence the involvement of both the carboxylic acid and the amino group in anchoring the organic compound on the solid surface. Linear natural amino acids became also active in the asymmetric Michael addition following adsorption on laponite and provided the opposite enantiomer in excess as compared with l-proline. The heterogeneous catalyst was applied in reactions of various carbonyl compounds and substituted nitrostyrene derivatives. Based on results obtained in this study combined with the previously reported amino acid catalyzed reactions on solid surfaces and the recently revisited reaction mechanism of this asymmetric addition a plausible reaction pathway occurring on the surface was proposed.

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Section: Resultssupporting

confidence: 60%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Surface‐Improved Asymmetric Michael Addition Catalyzed by Amino Acids Adsorbed on Laponite

et al. 2018

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“…Szerves közegű aszimmetrikus aldol-reakciókban aceton és aldehidek között enantioszelektivitás-inverziót tapasztaltak Li és munkatársai [48] az L-prolin γ-Al2O3 felületén történő adszorpciójával képződött L-prolin/γ-Al2O3 bifunkciós szerves-szervetlen hibrid katalizátoron. A tapasztalt jelenséget kutatócsoportunk is vizsgálta a korábbiakban [49].…”

Section: Enantioszelektivitás-inverzió Az L-prolinnal Katalizált Szerunclassified

L-aminosav-származékokkal és immobilizált oligopeptidekkel katalizált aszimmetrikus aldolreakciók sztereoszelektivitásának szabályozása

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Cella

Stefani

2018

Green Techniques for Organic Synthesis and Medicinal Chemistry

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Reversal of Enantioselectivity in Aldol Reaction: New Data on Proline/γ-Alumina Organic–Inorganic Hybrid Catalysts

Cited by 13 publications

References 26 publications

Surface‐Improved Asymmetric Michael Addition Catalyzed by Amino Acids Adsorbed on Laponite

Surface‐Improved Asymmetric Michael Addition Catalyzed by Amino Acids Adsorbed on Laponite

L-aminosav-származékokkal és immobilizált oligopeptidekkel katalizált aszimmetrikus aldolreakciók sztereoszelektivitásának szabályozása

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