Yongyue Luo, Wenyan Tian, Yang Zhou, Chuangchuang He, Xuebing Ma
{"title":"Efficient homogeneous-like enantioselective catalysis of a bulky chiral catalyst: covalent immobilization of chiral spirocyclic phosphoric acid onto polystyrene brushes grafted on SiO<sub>2</sub> nanospheres.","authors":"Yongyue Luo, Wenyan Tian, Yang Zhou, Chuangchuang He, Xuebing Ma","doi":"10.1039/d5ob00641d","DOIUrl":null,"url":null,"abstract":"<p><p>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 (<i>R</i>)-6,6'-di(9-anthryl)spirobiindane phosphoric acid ((<i>R</i>)-AnSPA) <i>via</i> Friedel-Crafts alkylation onto SiO<sub>2</sub>-grafted poly(<i>p</i>-vinylbenzyl chloride) (PVBC) brushes (PVBC@SiO<sub>2</sub>) and hollow mesoporous PVBC nanospheres (HMPNs), affording supported organocatalysts (AnSPA#PVBC@SiO<sub>2</sub> and AnSPA@HMPNs), respectively. Owing to the good dispersibility of PVBC brushes in organic solvents, the PVBC brush-anchored (<i>R</i>)-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 (<i>R</i>)-AnSPA, the PVBC brush-anchored (<i>R</i>)-AnSPA shows decrements in yield and enantioselectivity below 2%. However, the HMPN-anchored (<i>R</i>)-AnSPA shows larger decrements in yields (3-6%) and enantioselectivities (3-7% ee). Furthermore, AnSPA#PVBC@SiO<sub>2</sub> exhibits good reusability in enantioselective desymmetrization with no significant decreases in yield and enantioselectivity. Particularly, the deactivated AnSPA#PVBC@SiO<sub>2</sub>, caused by the hydrolysis of phosphate ester in (<i>R</i>)-AnSPA, can be easily renovated to its fresh state by dealing with POCl<sub>3</sub>. Overall, the direct immobilization of (<i>R</i>)-AnSPA onto PVBC brushes and renovation of deactivated (<i>R</i>)-AnSPA provide an effective strategy for achieving high sustainability of expensive chiral spirocyclic phosphoric acids in large-scale synthesis.</p>","PeriodicalId":96,"journal":{"name":"Organic & Biomolecular Chemistry","volume":" ","pages":""},"PeriodicalIF":2.9000,"publicationDate":"2025-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Organic & Biomolecular Chemistry","FirstCategoryId":"92","ListUrlMain":"https://doi.org/10.1039/d5ob00641d","RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"CHEMISTRY, ORGANIC","Score":null,"Total":0}
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.
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.