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Updated: Mar 21, 2026
A Microwave-Assisted Direct Heteroarylation of Ketones Using Transition Metal Catalysis
Published on: February 16, 2020
Asymmetric Hydrogenation of 3-Substituted Pyridinium Salts
Marc Renom-Carrasco1,2, Piotr Gajewski1,2, Luca Pignataro2
1DSM Ahead R&D B.V.-Innovative Synthesis, P. O. Box 18, 6160 MD, Geleen, The Netherlands.
Abstract:
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 Et3 N, 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.
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