New data to the origin of rate enhancement on the Pt-cinchona catalyzed enantioselective hydrogenation of activated ketones using continuous-flow fixed-bed reactor system

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Abstract

A study on the origin of rate enhancement (RE) in the enantioselective heterogeneous catalytic hydrogenation of methyl benzoylformate (MBF), ketopantolactone (KPL) and pyruvic aldehyde dimethyl acetal (PA) under the Orito reaction conditions over Pt catalyst modified with parent cinchona alkaloids, as compared to the unmodified catalyst is presented. The hydrogenations were carried out in continuous-flow fixed-bed reactor system over 20-100 mg Pt/Al2O3 catalyst in 1 mL min-1 flow of toluene/acetic acid 9/1 solvent mixture under 40-80 bar H2 pressure, at 283 or 293 K using 0.044-2 mM modifier concentration and 45 mM substrate concentration. Our results obtained using racemic hydrogenations followed by three changes of the chiral modifier (on the same catalyst) supported the so-called "ligand acceleration" phenomenon in the enantioselective hydrogenation of activated ketones such as MBF, KPL and PA. In our opinion, RE produced by the first modifier added after racemic hydrogenation can also be explained by the purifying effect of the cinchona. REs observed following further exchanges of modifiers are indicative of the intrinsic character of the phenomenon. This research suggested that the origin of enantiodifferentiation and rate enhancement is the same, namely, both may be traced back-probably in different ways-to the role of the intermediate complexes of the hydrogenation, to its formation and transformation, which in turn depends on numerous factors.

Original languageEnglish
Pages (from-to)245-253
Number of pages9
JournalJournal of Catalysis
Volume260
Issue number2
DOIs
Publication statusPublished - Dec 10 2008

Fingerprint

Cinchona
Ketones
ketones
Hydrogenation
hydrogenation
beds
reactors
augmentation
catalysts
Catalysts
Cinchona Alkaloids
Pyruvaldehyde
acetals
alkaloids
Toluene
Aldehydes
aldehydes
acetic acid
Catalyst supports
Acetic acid

Keywords

  • Asymmetric hydrogenation
  • Cinchona alkaloids
  • Continuous-flow fixed-bed-reactor
  • Ketopantolactone
  • Ligand acceleration
  • Methyl benzoylformate
  • Origin of rate enhancement
  • Platinum
  • Pyruvic aldehyde dimethyl acetal

ASJC Scopus subject areas

  • Catalysis
  • Physical and Theoretical Chemistry

Cite this

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title = "New data to the origin of rate enhancement on the Pt-cinchona catalyzed enantioselective hydrogenation of activated ketones using continuous-flow fixed-bed reactor system",
abstract = "A study on the origin of rate enhancement (RE) in the enantioselective heterogeneous catalytic hydrogenation of methyl benzoylformate (MBF), ketopantolactone (KPL) and pyruvic aldehyde dimethyl acetal (PA) under the Orito reaction conditions over Pt catalyst modified with parent cinchona alkaloids, as compared to the unmodified catalyst is presented. The hydrogenations were carried out in continuous-flow fixed-bed reactor system over 20-100 mg Pt/Al2O3 catalyst in 1 mL min-1 flow of toluene/acetic acid 9/1 solvent mixture under 40-80 bar H2 pressure, at 283 or 293 K using 0.044-2 mM modifier concentration and 45 mM substrate concentration. Our results obtained using racemic hydrogenations followed by three changes of the chiral modifier (on the same catalyst) supported the so-called {"}ligand acceleration{"} phenomenon in the enantioselective hydrogenation of activated ketones such as MBF, KPL and PA. In our opinion, RE produced by the first modifier added after racemic hydrogenation can also be explained by the purifying effect of the cinchona. REs observed following further exchanges of modifiers are indicative of the intrinsic character of the phenomenon. This research suggested that the origin of enantiodifferentiation and rate enhancement is the same, namely, both may be traced back-probably in different ways-to the role of the intermediate complexes of the hydrogenation, to its formation and transformation, which in turn depends on numerous factors.",
keywords = "Asymmetric hydrogenation, Cinchona alkaloids, Continuous-flow fixed-bed-reactor, Ketopantolactone, Ligand acceleration, Methyl benzoylformate, Origin of rate enhancement, Platinum, Pyruvic aldehyde dimethyl acetal",
author = "G. Sz{\"o}llősi and S. Cser{\'e}nyi and F. F{\"u}l{\"o}p and M. Bart{\'o}k",
year = "2008",
month = "12",
day = "10",
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pages = "245--253",
journal = "Journal of Catalysis",
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T1 - New data to the origin of rate enhancement on the Pt-cinchona catalyzed enantioselective hydrogenation of activated ketones using continuous-flow fixed-bed reactor system

AU - Szöllősi, G.

AU - Cserényi, S.

AU - Fülöp, F.

AU - Bartók, M.

PY - 2008/12/10

Y1 - 2008/12/10

N2 - A study on the origin of rate enhancement (RE) in the enantioselective heterogeneous catalytic hydrogenation of methyl benzoylformate (MBF), ketopantolactone (KPL) and pyruvic aldehyde dimethyl acetal (PA) under the Orito reaction conditions over Pt catalyst modified with parent cinchona alkaloids, as compared to the unmodified catalyst is presented. The hydrogenations were carried out in continuous-flow fixed-bed reactor system over 20-100 mg Pt/Al2O3 catalyst in 1 mL min-1 flow of toluene/acetic acid 9/1 solvent mixture under 40-80 bar H2 pressure, at 283 or 293 K using 0.044-2 mM modifier concentration and 45 mM substrate concentration. Our results obtained using racemic hydrogenations followed by three changes of the chiral modifier (on the same catalyst) supported the so-called "ligand acceleration" phenomenon in the enantioselective hydrogenation of activated ketones such as MBF, KPL and PA. In our opinion, RE produced by the first modifier added after racemic hydrogenation can also be explained by the purifying effect of the cinchona. REs observed following further exchanges of modifiers are indicative of the intrinsic character of the phenomenon. This research suggested that the origin of enantiodifferentiation and rate enhancement is the same, namely, both may be traced back-probably in different ways-to the role of the intermediate complexes of the hydrogenation, to its formation and transformation, which in turn depends on numerous factors.

AB - A study on the origin of rate enhancement (RE) in the enantioselective heterogeneous catalytic hydrogenation of methyl benzoylformate (MBF), ketopantolactone (KPL) and pyruvic aldehyde dimethyl acetal (PA) under the Orito reaction conditions over Pt catalyst modified with parent cinchona alkaloids, as compared to the unmodified catalyst is presented. The hydrogenations were carried out in continuous-flow fixed-bed reactor system over 20-100 mg Pt/Al2O3 catalyst in 1 mL min-1 flow of toluene/acetic acid 9/1 solvent mixture under 40-80 bar H2 pressure, at 283 or 293 K using 0.044-2 mM modifier concentration and 45 mM substrate concentration. Our results obtained using racemic hydrogenations followed by three changes of the chiral modifier (on the same catalyst) supported the so-called "ligand acceleration" phenomenon in the enantioselective hydrogenation of activated ketones such as MBF, KPL and PA. In our opinion, RE produced by the first modifier added after racemic hydrogenation can also be explained by the purifying effect of the cinchona. REs observed following further exchanges of modifiers are indicative of the intrinsic character of the phenomenon. This research suggested that the origin of enantiodifferentiation and rate enhancement is the same, namely, both may be traced back-probably in different ways-to the role of the intermediate complexes of the hydrogenation, to its formation and transformation, which in turn depends on numerous factors.

KW - Asymmetric hydrogenation

KW - Cinchona alkaloids

KW - Continuous-flow fixed-bed-reactor

KW - Ketopantolactone

KW - Ligand acceleration

KW - Methyl benzoylformate

KW - Origin of rate enhancement

KW - Platinum

KW - Pyruvic aldehyde dimethyl acetal

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SP - 245

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JO - Journal of Catalysis

JF - Journal of Catalysis

SN - 0021-9517

IS - 2

ER -