Issue 13, 2024

Preparations of spherical nanoparticles of chiral Cinchona alkaloid-based bridged silsesquioxanes and their use in heterogeneous catalysis of enantioselective reactions

Abstract

Two spherical nanoparticulate materials were prepared by base-catalyzed sol–gel hydrolysis/self-condensation of the bis-Cinchona alkaloid-phthalazine-based bridged bis(triethoxysilanes). For the purpose of comparing the catalytic properties, two compact materials were also prepared from the same precursors using a fluoride-catalyzed sol–gel process. All materials were characterized by SEM, TEM, solid-state 29Si NMR and 13C NMR, TGA, and FTIR. The prepared silsesquioxane-based materials were studied as potential heterogeneous catalysts for selected enantioselective reactions. The spherical material with regularly incorporated bis-quinine-phthalazine chiral units exhibited good to excellent enantioselectivities in osmium-catalyzed dihydroxylations of alkenes. Enantioselectivities observed in dihydroxylations of aromatic trans-alkenes were as excellent as those observed with the homogeneous catalyst (DHQ)2–PHAL. One compact and one nanoparticulate material was successfully recycled and reused five times without loss of enantioselectivity. Furthermore, both quinine-based and cinchonine-based materials were tested as heterogeneous organocatalysts for chlorolactonization of 4-arylpent-4-enoic acids. The materials showed only moderate enantioselectivities; however, these are the first heterogeneous catalysts for enantioselective chlorolactonization published so far.

Graphical abstract: Preparations of spherical nanoparticles of chiral Cinchona alkaloid-based bridged silsesquioxanes and their use in heterogeneous catalysis of enantioselective reactions

Supplementary files

Article information

Article type
Paper
Submitted
06 Dec 2023
Accepted
26 Feb 2024
First published
07 Mar 2024
This article is Open Access
Creative Commons BY-NC license

Nanoscale, 2024,16, 6696-6707

Preparations of spherical nanoparticles of chiral Cinchona alkaloid-based bridged silsesquioxanes and their use in heterogeneous catalysis of enantioselective reactions

D. Tetour, M. Novotná, J. Tatýrek, V. Máková, M. Stuchlík, C. Hobbs, M. Řezanka, M. Müllerová, V. Setnička, K. Dobšíková and J. Hodačová, Nanoscale, 2024, 16, 6696 DOI: 10.1039/D3NR06234A

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