Aldehyde and Ketone Hydroboration Mediated by a Heterogeneous Single-Site Molybdenum-Dioxo Catalyst: Scope and Mechanistic Implications

Yiqi Liu, Amol Agarwal, Liwei Ye, Yosi Kratish*, Tobin J. Marks*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Efficient hydroboration of aldehydes and ketones is demonstrated using a single-site MoO2 catalyst supported on activated carbon. Under mild conditions with low catalytic loadings, the reaction exhibits chemoselectivity towards carbonyl reduction over halides, alkene, alkyne, nitrile, and ester groups, affording high yields of desired products. Furthermore, competition studies between aldehyde and ketone reduction using HBpin and HBcat indicate that HBpin preferably functionalizes aldehydes, while HBcat can functionalize either substrate under specific conditions. Mechanistic studies suggest that the reaction proceeds via the initial formation of a molybdenum-hydride species upon B−H activation and subsequent molybdenum-alkoxide species upon carbonyl activation by the Mo center. The experimental activation energy of 14.3 kcal/mol alignssatisfactorily with the DFT computed ΔH of 18.7 kcal/mol, further supporting the proposed mechanism. Combined experimental/computational analyses reveal that excess HBpin can possibly deactivate the catalyst. The presence of excess benzaldehyde efficiently mitigates deactivation by HBpin, providing significantly higher catalyst recyclability. Overall, this non-toxic, air- and moisture-stable, active, and selective catalyst demonstrates significant potential for green processes.

Original languageEnglish (US)
Article numbere202301417
JournalChemCatChem
Volume16
Issue number7
DOIs
StatePublished - Apr 8 2024

Keywords

  • heterogeneous catalysis
  • hydroboration
  • mechanistic studies
  • molybdenum
  • single-site catalysts

ASJC Scopus subject areas

  • Catalysis
  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry

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