Efficient homogeneous-like enantioselective catalysis of a bulky chiral catalyst: covalent immobilization of chiral spirocyclic phosphoric acid onto polystyrene brushes grafted on SiO2 nanospheres.

IF 2.9 3区 化学 Q1 CHEMISTRY, ORGANIC
Yongyue Luo, Wenyan Tian, Yang Zhou, Chuangchuang He, Xuebing Ma
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引用次数: 0

Abstract

To solve the mass transfer limitation and multi-step immobilization of bulky chiral phosphoric acids in heterogeneous asymmetric catalysis, this paper develops a direct immobilization of (R)-6,6'-di(9-anthryl)spirobiindane phosphoric acid ((R)-AnSPA) via Friedel-Crafts alkylation onto SiO2-grafted poly(p-vinylbenzyl chloride) (PVBC) brushes (PVBC@SiO2) and hollow mesoporous PVBC nanospheres (HMPNs), affording supported organocatalysts (AnSPA#PVBC@SiO2 and AnSPA@HMPNs), respectively. Owing to the good dispersibility of PVBC brushes in organic solvents, the PVBC brush-anchored (R)-AnSPA with an open-ended structure enables the enantioselective desymmetrization of oxetanes with mercaptobenzothiazoles to proceed in a homogeneous-like manner, leading to the improved mass transfer of reactants due to alleviative steric hindrance. Compared to the homogeneous (R)-AnSPA, the PVBC brush-anchored (R)-AnSPA shows decrements in yield and enantioselectivity below 2%. However, the HMPN-anchored (R)-AnSPA shows larger decrements in yields (3-6%) and enantioselectivities (3-7% ee). Furthermore, AnSPA#PVBC@SiO2 exhibits good reusability in enantioselective desymmetrization with no significant decreases in yield and enantioselectivity. Particularly, the deactivated AnSPA#PVBC@SiO2, caused by the hydrolysis of phosphate ester in (R)-AnSPA, can be easily renovated to its fresh state by dealing with POCl3. Overall, the direct immobilization of (R)-AnSPA onto PVBC brushes and renovation of deactivated (R)-AnSPA provide an effective strategy for achieving high sustainability of expensive chiral spirocyclic phosphoric acids in large-scale synthesis.

大体积手性催化剂的高效类均相对映选择性催化:手性螺旋环磷酸共价固定在SiO2纳米球接枝的聚苯乙烯刷上。
为了解决大体积手性磷酸在非均相不对称催化中的传质限制和多步固定化问题,本文通过friede - crafts烷基化将(R)-6,6′-二(9-蒽基)螺旋比茚磷酸((R)-AnSPA)直接固定化在二氧化硅接枝的聚对苯基氯化乙烯(PVBC)刷(PVBC@SiO2)和中空介孔PVBC纳米球(hmpn)上,分别提供负载的有机催化剂(AnSPA#PVBC@SiO2和AnSPA@HMPNs)。由于PVBC电刷在有机溶剂中的良好分散性,具有开放式结构的PVBC电刷锚定(R)-AnSPA可以使氧烷与巯基苯并噻唑的对映选择性去对称以均匀的方式进行,从而由于减轻了空间位阻而改善了反应物的传质。与均相(R)-AnSPA相比,PVBC刷锚定的(R)-AnSPA的产率和对映体选择性均低于2%。然而,hmpn锚定的(R)-AnSPA显示出更大的产率(3-6%)和对映选择性(3-7% ee)的下降。此外,AnSPA#PVBC@SiO2在对映选择性去对称中表现出良好的可重复使用性,且产率和对映选择性没有显著降低。特别是(R)-AnSPA中磷酸酯水解引起的失活AnSPA#PVBC@SiO2,通过POCl3处理,可以很容易地恢复到新鲜状态。综上所述,(R)-AnSPA直接固定在PVBC刷上,并对失活的(R)-AnSPA进行修复,为实现昂贵的手性螺旋环磷酸在大规模合成中的高可持续性提供了有效的策略。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Organic & Biomolecular Chemistry
Organic & Biomolecular Chemistry 化学-有机化学
CiteScore
5.50
自引率
9.40%
发文量
1056
审稿时长
1.3 months
期刊介绍: Organic & Biomolecular Chemistry is an international journal using integrated research in chemistry-organic chemistry. Founded in 2003 by the Royal Society of Chemistry, the journal is published in Semimonthly issues and has been indexed by SCIE, a leading international database. The journal focuses on the key research and cutting-edge progress in the field of chemistry-organic chemistry, publishes and reports the research results in this field in a timely manner, and is committed to becoming a window and platform for rapid academic exchanges among peers in this field. The journal's impact factor in 2023 is 2.9, and its CiteScore is 5.5.
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