Study of enantioselective hydrogenation of bulky esters of phenylglyoxylic acid on Pt-CD and Pt-β-ICN chiral catalysts: Steric effect of ester groups and inversion of enantioselectivity

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Abstract

Enantioselective hydrogenation of seven different esters of phenylglyoxylic acid was investigated by variation of the bulkiness at ester side of the substrates [Ph{single bond}C(O){single bond}C(O)OR, R = Me (l), cyclohexyl (2), adamantyl (3), cis-decahydro-1-naphthyl (4), phenyl (5), 1-naphthyl (6), 2-naphthyl (7)] on Pt-alumina-cinchonidine (CD) and Pt-alumina-β-isocinchonine (β-ICN) chiral catalysts using mild experimental conditions (273 K and room temperature, hydrogen pressure of 1-25 bar) in solvents of AcOH and toluene. Hydrogenation on Pt-alumina-CD chiral catalyst produced high values of ee for all but the 5 and 7 compounds. The formation of (R)-mandelic acid esters was 86-91% in AcOH and 79-94% in toluene. The experiments verified the general applicability of the Orito reaction in the preparation of enantiomers of α-hydroxyesters. Under the experimental conditions applied, the magnitude of ee is affected by the steric size of α-ketoesters and by solvents. In the enantioselective hydrogenation of substrates over a Pt-alumina-β-ICN catalyst in toluene, inversion of enantioselectivity occurred; (R)-mandelic acid esters formed with a medium ee of 30-54%. The conformation of the adsorbed modifier plays a more determining role than the bulkiness of the substrate in the formation of the intermediate complex responsible for enantioselection.

Original languageEnglish
Pages (from-to)149-154
Number of pages6
JournalJournal of Catalysis
Volume241
Issue number1
DOIs
Publication statusPublished - Jul 1 2006

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Aluminum Oxide
Enantioselectivity
Hydrogenation
hydrogenation
esters
Esters
Toluene
Alumina
aluminum oxides
inversions
toluene
catalysts
acids
Catalysts
Acids
Substrates
Enantiomers
enantiomers
Conformations
Hydrogen

Keywords

  • Chiral hydrogenation
  • Cinchonidine and β-isocinchonine
  • Conformation
  • Intermediate
  • Inversion of enantioselectivity
  • Phenylglyoxylic acid esters
  • Pt-alumina

ASJC Scopus subject areas

  • Catalysis
  • Process Chemistry and Technology

Cite this

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title = "Study of enantioselective hydrogenation of bulky esters of phenylglyoxylic acid on Pt-CD and Pt-β-ICN chiral catalysts: Steric effect of ester groups and inversion of enantioselectivity",
abstract = "Enantioselective hydrogenation of seven different esters of phenylglyoxylic acid was investigated by variation of the bulkiness at ester side of the substrates [Ph{single bond}C(O){single bond}C(O)OR, R = Me (l), cyclohexyl (2), adamantyl (3), cis-decahydro-1-naphthyl (4), phenyl (5), 1-naphthyl (6), 2-naphthyl (7)] on Pt-alumina-cinchonidine (CD) and Pt-alumina-β-isocinchonine (β-ICN) chiral catalysts using mild experimental conditions (273 K and room temperature, hydrogen pressure of 1-25 bar) in solvents of AcOH and toluene. Hydrogenation on Pt-alumina-CD chiral catalyst produced high values of ee for all but the 5 and 7 compounds. The formation of (R)-mandelic acid esters was 86-91{\%} in AcOH and 79-94{\%} in toluene. The experiments verified the general applicability of the Orito reaction in the preparation of enantiomers of α-hydroxyesters. Under the experimental conditions applied, the magnitude of ee is affected by the steric size of α-ketoesters and by solvents. In the enantioselective hydrogenation of substrates over a Pt-alumina-β-ICN catalyst in toluene, inversion of enantioselectivity occurred; (R)-mandelic acid esters formed with a medium ee of 30-54{\%}. The conformation of the adsorbed modifier plays a more determining role than the bulkiness of the substrate in the formation of the intermediate complex responsible for enantioselection.",
keywords = "Chiral hydrogenation, Cinchonidine and β-isocinchonine, Conformation, Intermediate, Inversion of enantioselectivity, Phenylglyoxylic acid esters, Pt-alumina",
author = "K. Sz{\"o}ri and K. Bal{\'a}zsik and K. Felf{\"o}ldi and M. Bart{\'o}k",
year = "2006",
month = "7",
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doi = "10.1016/j.jcat.2006.04.027",
language = "English",
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journal = "Journal of Catalysis",
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T1 - Study of enantioselective hydrogenation of bulky esters of phenylglyoxylic acid on Pt-CD and Pt-β-ICN chiral catalysts

T2 - Steric effect of ester groups and inversion of enantioselectivity

AU - Szöri, K.

AU - Balázsik, K.

AU - Felföldi, K.

AU - Bartók, M.

PY - 2006/7/1

Y1 - 2006/7/1

N2 - Enantioselective hydrogenation of seven different esters of phenylglyoxylic acid was investigated by variation of the bulkiness at ester side of the substrates [Ph{single bond}C(O){single bond}C(O)OR, R = Me (l), cyclohexyl (2), adamantyl (3), cis-decahydro-1-naphthyl (4), phenyl (5), 1-naphthyl (6), 2-naphthyl (7)] on Pt-alumina-cinchonidine (CD) and Pt-alumina-β-isocinchonine (β-ICN) chiral catalysts using mild experimental conditions (273 K and room temperature, hydrogen pressure of 1-25 bar) in solvents of AcOH and toluene. Hydrogenation on Pt-alumina-CD chiral catalyst produced high values of ee for all but the 5 and 7 compounds. The formation of (R)-mandelic acid esters was 86-91% in AcOH and 79-94% in toluene. The experiments verified the general applicability of the Orito reaction in the preparation of enantiomers of α-hydroxyesters. Under the experimental conditions applied, the magnitude of ee is affected by the steric size of α-ketoesters and by solvents. In the enantioselective hydrogenation of substrates over a Pt-alumina-β-ICN catalyst in toluene, inversion of enantioselectivity occurred; (R)-mandelic acid esters formed with a medium ee of 30-54%. The conformation of the adsorbed modifier plays a more determining role than the bulkiness of the substrate in the formation of the intermediate complex responsible for enantioselection.

AB - Enantioselective hydrogenation of seven different esters of phenylglyoxylic acid was investigated by variation of the bulkiness at ester side of the substrates [Ph{single bond}C(O){single bond}C(O)OR, R = Me (l), cyclohexyl (2), adamantyl (3), cis-decahydro-1-naphthyl (4), phenyl (5), 1-naphthyl (6), 2-naphthyl (7)] on Pt-alumina-cinchonidine (CD) and Pt-alumina-β-isocinchonine (β-ICN) chiral catalysts using mild experimental conditions (273 K and room temperature, hydrogen pressure of 1-25 bar) in solvents of AcOH and toluene. Hydrogenation on Pt-alumina-CD chiral catalyst produced high values of ee for all but the 5 and 7 compounds. The formation of (R)-mandelic acid esters was 86-91% in AcOH and 79-94% in toluene. The experiments verified the general applicability of the Orito reaction in the preparation of enantiomers of α-hydroxyesters. Under the experimental conditions applied, the magnitude of ee is affected by the steric size of α-ketoesters and by solvents. In the enantioselective hydrogenation of substrates over a Pt-alumina-β-ICN catalyst in toluene, inversion of enantioselectivity occurred; (R)-mandelic acid esters formed with a medium ee of 30-54%. The conformation of the adsorbed modifier plays a more determining role than the bulkiness of the substrate in the formation of the intermediate complex responsible for enantioselection.

KW - Chiral hydrogenation

KW - Cinchonidine and β-isocinchonine

KW - Conformation

KW - Intermediate

KW - Inversion of enantioselectivity

KW - Phenylglyoxylic acid esters

KW - Pt-alumina

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U2 - 10.1016/j.jcat.2006.04.027

DO - 10.1016/j.jcat.2006.04.027

M3 - Article

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VL - 241

SP - 149

EP - 154

JO - Journal of Catalysis

JF - Journal of Catalysis

SN - 0021-9517

IS - 1

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