Cobalt-Catalyzed Asymmetric Hydrogenation of Enamides: Insights into Mechanisms and Solvent Effects

Ljiljana Pavlovic, Lauren N. Mendelsohn, Hongyu Zhong, Paul J. Chirik, Kathrin H. Hopmann

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1 Scopus citations

Abstract

The mechanistic details of the (PhBPE)Co-catalyzed asymmetric hydrogenation of enamides are investigated using computational and experimental approaches. Four mechanistic possibilities are compared: a direct Co(0)/Co(II) redox path, a metathesis pathway, a nonredox Co(II) mechanism featuring an aza-metallacycle, and a possible enamide-imine tautomerization pathway. The results indicate that the operative mechanism may depend on the type of enamide. Explicit solvent is found to be crucial for the stabilization of transition states and for a proper estimation of the enantiomeric excess. The combined results highlight the complexity of base-metal-catalyzed hydrogenations but do also provide guiding principles for a mechanistic understanding of these systems, where protic substrates can be expected to open up nonredox hydrogenation pathways.

Original languageEnglish (US)
Pages (from-to)1872-1882
Number of pages11
JournalOrganometallics
Volume41
Issue number14
DOIs
StatePublished - Jul 25 2022

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry

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