Surface‐Improved Asymmetric Michael Addition Catalyzed by Amino Acids Adsorbed on Laponite,Advanced Synthesis & Catalysis

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Surface‐Improved Asymmetric Michael Addition Catalyzed by Amino Acids Adsorbed on Laponite
Advanced Synthesis & Catalysis ( IF 4.4 ) Pub Date : 2018-03-23 , DOI: 10.1002/adsc.201701627
György Szőllősi ₁ , Dániel Gombkötő ₂ , Attila Zsolt Mogyorós ₂ , Ferenc Fülöp _{1,

3}

Affiliation

An unprecedented enantioselectivity increase was observed in the presence of inorganic oxides in the asymmetric Michael addition of aldehydes to trans‐β‐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.

中文翻译：

皂石上吸附的氨基酸催化表面改性的不对称迈克尔加成反应

在氨基酸不对称地将醛不对称地添加到氨基酸催化的反式-β-硝基苯乙烯衍生物中的无机氧化物存在下，观察到了前所未有的对映选择性增加。最佳结果是在到达升使用合成锂皂石RD作为添加剂，接近使用合成手性有机催化剂获得的那些-脯氨酸催化加成线性醛。在我们的研究中，我们表明不对称迈克尔加成反应是由原位形成的有机-无机杂化材料催化的通过氨基酸在固体表面上的吸附。手性固体催化剂可以在保持立体选择性的情况下进行预制备和循环使用，表现出活性的缓慢降低，可以通过在重复使用过程中添加脯氨酸来恢复。通过FT-IR光谱和XRD测量表征手性杂化材料表明脯氨酸锚定在锂皂石颗粒的表面上。手性有机催化剂结构的作用被用来证明羧酸和氨基都参与了将有机化合物锚固在固体表面上。线性天然氨基酸在皂石上吸附后在不对称迈克尔加成反应中也具有活性，并提供了相对于l过量的相反对映体脯氨酸。将该非均相催化剂应用于各种羰基化合物和取代的硝基苯乙烯衍生物的反应中。基于在这项研究中获得的结果，结合先前报道的在固体表面上氨基酸催化的反应以及这种不对称加成的最近重新考虑的反应机理，提出了在表面上发生的合理反应途径。

更新日期：2018-03-23

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