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Enantioselective decarboxylation of beta-keto esters with Pd/amino alcohol systems: successive metal catalysis and organocatalysis.
Chemistry. 2008; 14(9):2699-708.C

Abstract

The kinetics and mechanisms of one-pot cascade reactions of racemic beta-keto esters to give chiral ketones in the presence of Pd/C-chiral amino alcohol catalyst systems were studied. Transformation of 2-methyl-1-tetralone-2-carboxylic acid benzyl ester (1) into 2-methyl-1-tetralone (4) in the presence of Pd/C and cinchona alkaloids or ephedrine was chosen as a model reaction. After the first reaction step, the Pd-catalysed debenzylation of 1 to afford the corresponding beta-keto acid (2), there are two possible reaction routes that may be catalysed by the chiral amino alcohol in solution or by Pd(0) sites on the metal surface in cooperation with the adsorbed amino alcohol. The reaction intermediate 2 was synthesized, and the kinetics of decarboxylation were followed by NMR, UV and IR spectroscopy. The studies revealed that the role of Pd is to trigger the reaction series by deprotection of 1. The subsequent dominant reaction route from the racemic beta-keto acid 2 to the chiral ketone 4 is catalysed by the chiral amino alcohol in the liquid phase. It is shown that kinetic resolution of the diastereomeric salt of rac-2 and the chiral amino alcohol plays a key role in the enantioselection. High enantioselectivity necessitates an amino alcohol/rac-2 ratio of at least 2. A high ratio favours the formation of 1:1 amino alcohol/acid diastereomeric complexes, and the second amino alcohol molecule may be responsible for the enantioselective protonation of 2 in the diastereomeric complex.

Authors+Show Affiliations

Institute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, ETH Zurich, Hönggerberg, HCI, 8093 Zürich, Switzerland.No affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

18228542

Citation

Kukula, Pavel, et al. "Enantioselective Decarboxylation of Beta-keto Esters With Pd/amino Alcohol Systems: Successive Metal Catalysis and Organocatalysis." Chemistry (Weinheim an Der Bergstrasse, Germany), vol. 14, no. 9, 2008, pp. 2699-708.
Kukula P, Matousek V, Mallat T, et al. Enantioselective decarboxylation of beta-keto esters with Pd/amino alcohol systems: successive metal catalysis and organocatalysis. Chemistry. 2008;14(9):2699-708.
Kukula, P., Matousek, V., Mallat, T., & Baiker, A. (2008). Enantioselective decarboxylation of beta-keto esters with Pd/amino alcohol systems: successive metal catalysis and organocatalysis. Chemistry (Weinheim an Der Bergstrasse, Germany), 14(9), 2699-708. https://doi.org/10.1002/chem.200701652
Kukula P, et al. Enantioselective Decarboxylation of Beta-keto Esters With Pd/amino Alcohol Systems: Successive Metal Catalysis and Organocatalysis. Chemistry. 2008;14(9):2699-708. PubMed PMID: 18228542.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Enantioselective decarboxylation of beta-keto esters with Pd/amino alcohol systems: successive metal catalysis and organocatalysis. AU - Kukula,Pavel, AU - Matousek,Václav, AU - Mallat,Tamas, AU - Baiker,Alfons, PY - 2008/1/30/pubmed PY - 2008/6/17/medline PY - 2008/1/30/entrez SP - 2699 EP - 708 JF - Chemistry (Weinheim an der Bergstrasse, Germany) JO - Chemistry VL - 14 IS - 9 N2 - The kinetics and mechanisms of one-pot cascade reactions of racemic beta-keto esters to give chiral ketones in the presence of Pd/C-chiral amino alcohol catalyst systems were studied. Transformation of 2-methyl-1-tetralone-2-carboxylic acid benzyl ester (1) into 2-methyl-1-tetralone (4) in the presence of Pd/C and cinchona alkaloids or ephedrine was chosen as a model reaction. After the first reaction step, the Pd-catalysed debenzylation of 1 to afford the corresponding beta-keto acid (2), there are two possible reaction routes that may be catalysed by the chiral amino alcohol in solution or by Pd(0) sites on the metal surface in cooperation with the adsorbed amino alcohol. The reaction intermediate 2 was synthesized, and the kinetics of decarboxylation were followed by NMR, UV and IR spectroscopy. The studies revealed that the role of Pd is to trigger the reaction series by deprotection of 1. The subsequent dominant reaction route from the racemic beta-keto acid 2 to the chiral ketone 4 is catalysed by the chiral amino alcohol in the liquid phase. It is shown that kinetic resolution of the diastereomeric salt of rac-2 and the chiral amino alcohol plays a key role in the enantioselection. High enantioselectivity necessitates an amino alcohol/rac-2 ratio of at least 2. A high ratio favours the formation of 1:1 amino alcohol/acid diastereomeric complexes, and the second amino alcohol molecule may be responsible for the enantioselective protonation of 2 in the diastereomeric complex. SN - 0947-6539 UR - https://www.unboundmedicine.com/medline/citation/18228542/Enantioselective_decarboxylation_of_beta_keto_esters_with_Pd/amino_alcohol_systems:_successive_metal_catalysis_and_organocatalysis_ L2 - https://doi.org/10.1002/chem.200701652 DB - PRIME DP - Unbound Medicine ER -