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Article

Synthesis of Novel Crown Ether-Squaramides and Their Application as Phase-Transfer Catalysts

1
Department of Organic Chemistry and Technology, Budapest University of Technology and Economics, Szent Gellért tér 4, H-1111 Budapest, Hungary
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Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics, Szent Gellért tér 4, H-1111 Budapest, Hungary
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MS Proteomics Research Group, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar Tudósok körútja 2, H-1117 Budapest, Hungary
*
Author to whom correspondence should be addressed.
Academic Editors: Dimitrios Bikiaris and Maurizio Benaglia
Molecules 2021, 26(21), 6542; https://doi.org/10.3390/molecules26216542
Received: 15 September 2021 / Revised: 18 October 2021 / Accepted: 27 October 2021 / Published: 29 October 2021
(This article belongs to the Special Issue New Insights into the Preparation and Separation of Enantiomers)
This work presents the synthesis of six new phase-transfer organocatalysts in which the squaramide unit is directly linked to the nitrogen atom of an aza-crown ether. Four chiral skeletons, namely hydroquinine, quinine, cinchonine (cinchonas), and α-d-glucopyranoside were responsible for the asymmetric construction of an all-carbon quaternary stereogenic center in α-alkylation and Michael addition reactions of malonic esters. We investigated the effects of these different chiral units and that of crown ethers with different sizes on catalytic activity and enantioselectivity. During extensive parameter investigations, both conventional and emerging green solvents were screened, providing valuable α,α-disubstituted malonic ester derivatives with excellent yields (up to 98%). View Full-Text
Keywords: asymmetric catalysis; phase-transfer catalysis; enantioselectivity; allylation; crown compounds; carbohydrates; amino acids asymmetric catalysis; phase-transfer catalysis; enantioselectivity; allylation; crown compounds; carbohydrates; amino acids
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MDPI and ACS Style

Fehér, Z.; Richter, D.; Nagy, S.; Bagi, P.; Rapi, Z.; Simon, A.; Drahos, L.; Huszthy, P.; Bakó, P.; Kupai, J. Synthesis of Novel Crown Ether-Squaramides and Their Application as Phase-Transfer Catalysts. Molecules 2021, 26, 6542. https://doi.org/10.3390/molecules26216542

AMA Style

Fehér Z, Richter D, Nagy S, Bagi P, Rapi Z, Simon A, Drahos L, Huszthy P, Bakó P, Kupai J. Synthesis of Novel Crown Ether-Squaramides and Their Application as Phase-Transfer Catalysts. Molecules. 2021; 26(21):6542. https://doi.org/10.3390/molecules26216542

Chicago/Turabian Style

Fehér, Zsuzsanna, Dóra Richter, Sándor Nagy, Péter Bagi, Zsolt Rapi, András Simon, László Drahos, Péter Huszthy, Péter Bakó, and József Kupai. 2021. "Synthesis of Novel Crown Ether-Squaramides and Their Application as Phase-Transfer Catalysts" Molecules 26, no. 21: 6542. https://doi.org/10.3390/molecules26216542

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