Acid‐modified Halloysite Nanotubes as a Stereoselective Catalyst for Synthesis of 2H‐Chromene Derivatives by the Reaction of Isopulegol with Aldehydes,ChemCatChem

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Acid‐modified Halloysite Nanotubes as a Stereoselective Catalyst for Synthesis of 2H‐Chromene Derivatives by the Reaction of Isopulegol with Aldehydes
ChemCatChem ( IF 3.8 ) Pub Date : 2018-07-23 , DOI: 10.1002/cctc.201800974
Alexander Yu. Sidorenko ₁ , Anna V. Kravtsova ₁ , Atte Aho ₂ , Ivo Heinmaa ₃ , Konstantin P. Volcho ₄ , Nariman F. Salakhutdinov ₄ , Vladimir E. Agabekov ₁ , Dmitry Yu. Murzin ₂

Affiliation

Acid‐modified halloysite nanotubes were used for the first time as a stereoselective catalyst for synthesis of oxygen‐containing heterocycles applying of allyl alcohol (−)‐isopulegol condensation with aldehydes to the octahydro‐2H‐chromenol (4R‐ and 4S‐diastereomers) as an example. The catalysts were characterized by XRF, XRD, N₂‐adsorption, FTIR with pyridine and MAS NMR methods. A high ratio of 4R/4S diastereomers (7.6–14.5) under mild conditions in cyclohexane was considerably exceeding previously reported results. Unprecedented selectivity (79–83 %) to 4R isomer of thiophenyl‐substituted chromenol exhibiting high analgesic activity was achieved. An increase in stereoselectivity with a decrease in the halloysite drying temperature and catalyst acidity clearly indicates formation of 4R diastereomer on the weak Brønsted sites. This work is an example that control of the stereoselectivity of acid‐catalyzed organic reactions can be effectively carried out by varying water content on the aluminosilicate surface. Modified halloysite nanotubes can be considered as extremely promising catalysts for stereoselective synthesis of heterocyclic compounds.

中文翻译：

酸改性的埃洛石纳米管作为立体选择性催化剂，通过异戊二醇与醛的反应合成2H-H烯衍生物

酸改性的高岭土纳米管被用于第一次作为用于施加烯丙醇的含氧杂环的合成立体选择性催化剂（ - ） -异胡薄荷醇缩合与醛的八氢-2 ħ -chromenol（4 - [R -和4小号-非对映体）为例。通过XRF，XRD，N ₂吸附，带吡啶的FTIR和MAS NMR方法对催化剂进行了表征。在温和条件下，在环己烷中高比例的4 R / 4 S非对映异构体（7.6–14.5）大大超过了先前报道的结果。前所未有的选择性（79–83％）至4 R获得了具有高止痛活性的噻吩基取代的苯甲醇的异构体。立体选择性的增加，以及埃洛石干燥温度和催化剂酸度的降低，清楚地表明在弱的布朗斯台德位点上形成了4 R非对映异构体。这项工作就是一个例子，可以通过改变铝硅酸盐表面的水含量来有效地控制酸催化的有机反应的立体选择性。改性的埃洛石纳米管可以被认为是杂环化合物立体选择性合成的极有希望的催化剂。

更新日期：2018-07-23

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