Asymmetric Hydrogenation of 3-Substituted Pyridinium Salts

The use of an equivalent amount of an organic base leads to high enantiomeric excess in the asymmetric hydrogenation of N‐benzylated 3‐substituted pyridinium salts into the corresponding piperidines. Indeed, in the presence of Et3N, a Rh‐JosiPhos catalyst reduced a range of pyridinium salts with ee...

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Bibliographic Details
Published in:Chemistry : a European journal Vol. 22; no. 28; pp. 9528 - 9532
Main Authors: Renom-Carrasco, Marc, Gajewski, Piotr, Pignataro, Luca, de Vries, Johannes G., Piarulli, Umberto, Gennari, Cesare, Lefort, Laurent
Format: Journal Article
Language:English
Published: WEINHEIM Blackwell Publishing Ltd 04.07.2016
Wiley
Wiley Subscription Services, Inc
Subjects:
asymmetric catalysis
Asymmetry
Chemistry
Chemistry, Multidisciplinary
Equivalence
homogeneous catalysis
Hydrogenation
Isotopic labeling
Labyrinth
Pathways
Physical Sciences
Piperidine
Pyridines
reaction mechanisms
Salts
Science & Technology
SCOPE
MONODENTATE PHOSPHORAMIDITE LIGANDS
reaction mechanisms
QUINOLINES
asymmetric catalysis
DEHYDROAMINO ACID-DERIVATIVES
hydrogenation
MULTIPLE STEREOGENIC CENTERS
IRIDIUM-CATALYZED HYDROGENATION
HIGHLY ENANTIOSELECTIVE HYDROGENATION
pyridines
homogeneous catalysis
REDUCTION
PIPERIDINES
ISOQUINOLINIUM SALTS
ISSN:0947-6539, 1521-3765, 1521-3765
Online Access:Get full text
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Summary:The use of an equivalent amount of an organic base leads to high enantiomeric excess in the asymmetric hydrogenation of N‐benzylated 3‐substituted pyridinium salts into the corresponding piperidines. Indeed, in the presence of Et3N, a Rh‐JosiPhos catalyst reduced a range of pyridinium salts with ee values up to 90 %. The role of the base was elucidated with a mechanistic study involving the isolation of the various reaction intermediates and isotopic labeling experiments. Additionally, this study provided some evidence for an enantiodetermining step involving a dihydropyridine intermediate. Ariadne′s thread: The asymmetric hydrogenation of 3‐substitued pyridines has been achieved with up to 90 % ee. The use of an equivalent amount of an organic base turned out to be crucial to avoid unwanted pathways leading to non‐enantioselective reduction. An in‐depth investigation of the mechanism revealed a labyrinth of hydrogenation pathways with many dead ends (see figure).
Bibliography:ArticleID:CHEM201601501
European Commission
ark:/67375/WNG-7C78WR4T-T
ITN-EID "REDUCTO" - No. PITN-GA-2012-316371
istex:5906FA8FEBE3E02BBD230789F973CC92D9AAC2CF
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SourceType-Scholarly Journals-1
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ISSN:0947-6539
1521-3765
1521-3765
DOI:10.1002/chem.201601501