The mechanochemical implementation of the environmentally friendly asymmetric transfer hydrogenation of ketones

Kolcsár Vanessza Judit and Szőllősi György: The mechanochemical implementation of the environmentally friendly asymmetric transfer hydrogenation of ketones.

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Optically pure compounds are essential in the synthesis of pharmaceuticals, fragrances and pesticides. Asymmetric catalytic reactions are the most favorable methods to achieve high conversions and enantiomeric excesses in fast reactions, using only catalytic amount of the chirality sources. Hydrogenations and transfer hydrogenations are well-studied procedures to obtain optically pure chiral alcohols. The transfer hydrogenation is convenient, as it ensures the possibility to use a hydrogen donor compound instead of hydrogen gas to provide the necessary H atom. In the past few decades several synthetic chiral compounds were used as the ligand of the catalyst complex, however these days more environmentally friendly implementations are favored. The use of natural chiral compounds would provide great opportunities to carry out asymmetric catalytic reactions using less organic solvents and producing less hazardous waste. In our previous studies, we have developed an asymmetric catalytic system for the transfer hydrogenation of prochiral ketones using an in situ prepared Ru-chitosan complex in aqueous media. The catalyst prepared using the readily and easily available, biodegradable and inexpensive biopolymer provided good result in the transfer hydrogenation of various prochiral ketones in aqueous-phase reactions. In order to increase the preparative value of this method for preparing optically pure alcohols, we decided to use mechanical energy transmission instead of conventional thermally activated reactions carried out in magnetically stirred batch reactors. With the former method the reaction time can be reduced, as well as the volume of the used solvent and the produced waste. After the optimization of the reaction conditions in the transfer hydrogenation of 4-chromanone, we examined the reaction of various ketones and the obtained results were compared with those reached in reactions carried out conventionally. All the examined ketones were transformed in similar degrees and the chiral alcohols were obtained in high enantiomeric excesses (ee). The reactions were scaled up as well, to prepare the optically enriched compounds in mmol quantities.

Item Type: Conference or Workshop Item
Journal or Publication Title: Proceedings of the International Symposium on Analytical and Environmental Problems
Date: 2020
Volume: 26
ISBN: 978-963-306-771-0
Page Range: pp. 30-34
Language: English
Event Title: International Symposium on Analytical and Environmental Problems (26.) (2020) (Szeged)
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Uncontrolled Keywords: Környezetkémia
Additional Information: Bibliogr.: p. 33-34. ; összefoglalás angol nyelven
Subjects: 01. Natural sciences
01. Natural sciences > 01.04. Chemical sciences
Date Deposited: 2021. Nov. 16. 13:06
Last Modified: 2022. Aug. 08. 15:39

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