La[N(sime3)2]3-catalyzed deoxygenative reduction of amides with pinacolborane. scope and mechanism

Christopher J. Barger, Rachel D. Dicken, Victoria L. Weidner, Alessandro Motta, Tracy Lynn Lohr*, Tobin J. Marks

*Corresponding author for this work

Research output: Contribution to journalArticle

Abstract

Tris[N,N-bis(trimethylsilyl)amide]lanthanum (LaNTMS) is an efficient and selective homogeneous catalyst for the deoxygenative reduction of tertiary and secondary amides with pinacolborane (HBpin) at mild temperatures (25-60 °C). The reaction, which yields amines and O(Bpin)2, tolerates nitro, halide, and amino functional groups well, and this amide reduction is completely selective, with the exclusion of both competing inter- and intramolecular alkene/alkyne hydroboration. Kinetic studies indicate that amide reduction obeys an unusual mixed-order rate law which is proposed to originate from saturation of the catalyst complex with HBpin. Kinetic and thermodynamic studies, isotopic labeling, and DFT calculations using energetic span analysis suggest the role of a [(Me3Si)2N]2La-OCHR(NR′2)[HBpin] active catalyst, and hydride transfer is proposed to be ligand-centered. These results add to the growing list of transformations that commercially available LaNTMS is competent to catalyze, further underscoring the value and versatility of lanthanide complexes in homogeneous catalysis.

Original languageEnglish (US)
Pages (from-to)8019-8028
Number of pages10
JournalJournal of the American Chemical Society
Volume142
Issue number17
DOIs
StatePublished - Apr 29 2020

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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