Heterogeneous asymmetric reactions 20. Effect of ultrasonic variables on the enantiodifferentiation in cinchona-modified platinum-catalyzed sonochemical hydrogenations

Béla Török, K. Balázsik, Marianna Török, K. Felföldi, M. Bartók

Research output: Contribution to journalArticle

29 Citations (Scopus)

Abstract

The effect of sonochemical variables on a cinchona alkaloid modified Pt/Al2O3 catalyst system and its application in α-ketoester hydrogenation are described. The sonochemical pretreatment of these commercial Pt/Al2O3-cinchonidine catalysts resulted in excellent ee values (up to 92-98% ee) under mild experimental conditions. To gain more insight into the nature of the ultrasonic effect the reactions were screened under widely varied conditions (ultrasound source, frequency, insonation time). Besides investigating the reactions, the catalyst modifier system was also studied. The changes in metal particle size were determined by transmission electron microscopy, while the alteration of modifier concentration in the solvent upon sonication was followed by UV-vis spectroscopy. The transformation of the modifier during the pretreatment was detected by GC-MS and verified by NMR. Summarizing the results, the major effects of the sonochemical activation on the cinchona-modified supported Pt catalyst system can be described. The ultrasonic pretreatment increased the quantity of adsorbed cinchona and blocked its hydrogenation to provide more and highly stable chiral active sites for enantioselection.

Original languageEnglish
Pages (from-to)55-61
Number of pages7
JournalCatalysis Letters
Volume81
Issue number1-2
DOIs
Publication statusPublished - Jul 2002

Fingerprint

Cinchona
Platinum
Hydrogenation
hydrogenation
platinum
ultrasonics
Ultrasonics
pretreatment
catalysts
Catalysts
Ultrasonic effects
Cinchona Alkaloids
Sonication
Ultraviolet spectroscopy
Catalyst supports
alkaloids
metal particles
Metals
Chemical activation
Particle size

Keywords

  • α-ketoesters
  • Cinchona alkaloids
  • Enantioselective hydrogenation
  • Pt/AlO
  • Ultrasounds

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Catalysis

Cite this

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title = "Heterogeneous asymmetric reactions 20. Effect of ultrasonic variables on the enantiodifferentiation in cinchona-modified platinum-catalyzed sonochemical hydrogenations",
abstract = "The effect of sonochemical variables on a cinchona alkaloid modified Pt/Al2O3 catalyst system and its application in α-ketoester hydrogenation are described. The sonochemical pretreatment of these commercial Pt/Al2O3-cinchonidine catalysts resulted in excellent ee values (up to 92-98{\%} ee) under mild experimental conditions. To gain more insight into the nature of the ultrasonic effect the reactions were screened under widely varied conditions (ultrasound source, frequency, insonation time). Besides investigating the reactions, the catalyst modifier system was also studied. The changes in metal particle size were determined by transmission electron microscopy, while the alteration of modifier concentration in the solvent upon sonication was followed by UV-vis spectroscopy. The transformation of the modifier during the pretreatment was detected by GC-MS and verified by NMR. Summarizing the results, the major effects of the sonochemical activation on the cinchona-modified supported Pt catalyst system can be described. The ultrasonic pretreatment increased the quantity of adsorbed cinchona and blocked its hydrogenation to provide more and highly stable chiral active sites for enantioselection.",
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AU - Török, Béla

AU - Balázsik, K.

AU - Török, Marianna

AU - Felföldi, K.

AU - Bartók, M.

PY - 2002/7

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N2 - The effect of sonochemical variables on a cinchona alkaloid modified Pt/Al2O3 catalyst system and its application in α-ketoester hydrogenation are described. The sonochemical pretreatment of these commercial Pt/Al2O3-cinchonidine catalysts resulted in excellent ee values (up to 92-98% ee) under mild experimental conditions. To gain more insight into the nature of the ultrasonic effect the reactions were screened under widely varied conditions (ultrasound source, frequency, insonation time). Besides investigating the reactions, the catalyst modifier system was also studied. The changes in metal particle size were determined by transmission electron microscopy, while the alteration of modifier concentration in the solvent upon sonication was followed by UV-vis spectroscopy. The transformation of the modifier during the pretreatment was detected by GC-MS and verified by NMR. Summarizing the results, the major effects of the sonochemical activation on the cinchona-modified supported Pt catalyst system can be described. The ultrasonic pretreatment increased the quantity of adsorbed cinchona and blocked its hydrogenation to provide more and highly stable chiral active sites for enantioselection.

AB - The effect of sonochemical variables on a cinchona alkaloid modified Pt/Al2O3 catalyst system and its application in α-ketoester hydrogenation are described. The sonochemical pretreatment of these commercial Pt/Al2O3-cinchonidine catalysts resulted in excellent ee values (up to 92-98% ee) under mild experimental conditions. To gain more insight into the nature of the ultrasonic effect the reactions were screened under widely varied conditions (ultrasound source, frequency, insonation time). Besides investigating the reactions, the catalyst modifier system was also studied. The changes in metal particle size were determined by transmission electron microscopy, while the alteration of modifier concentration in the solvent upon sonication was followed by UV-vis spectroscopy. The transformation of the modifier during the pretreatment was detected by GC-MS and verified by NMR. Summarizing the results, the major effects of the sonochemical activation on the cinchona-modified supported Pt catalyst system can be described. The ultrasonic pretreatment increased the quantity of adsorbed cinchona and blocked its hydrogenation to provide more and highly stable chiral active sites for enantioselection.

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KW - Ultrasounds

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