Catalyst-Free Transfer Hydrogenation from Amine-Borane Small Oligomers.
Louis Le Moigne1, Tommaso Posenato2, David Gajan3
1Univ Lyon, Université Claude Bernard Lyon 1, CNRS, CNES, ArianeGroup, LHCEP, UMR 5278, Bât. Raulin, 2 rue Victor Grignard, 69622, Villeurbanne, France.
Chemistry (Weinheim an Der Bergstrasse, Germany)
|October 10, 2023
Summary
New amine-borane oligomers efficiently catalyze transfer hydrogenations. These compounds bridge molecular reductants and polymers, offering insights into reactivity across different scales.
Area of Science:
- Organic Chemistry
- Catalysis
- Polymer Chemistry
Background:
- Amine-borane complexes are valuable reducing agents.
- Understanding the relationship between molecular structure and reactivity is crucial.
- Polymeric amine-boranes have shown promise in catalysis.
Purpose of the Study:
- To synthesize and characterize amine-borane dimers and oligomers with controlled properties.
- To evaluate the catalytic activity of these compounds in transfer hydrogenation reactions.
- To investigate the structural characteristics of post-reaction boron-containing materials.
Main Methods:
- AA/BB polycondensation reactions controlled by capping agents.
- Transfer hydrogenation of various unsaturated compounds (aldehydes, ketones, imines, alkenes, alkynes).
- Solid-state Nuclear Magnetic Resonance (NMR) spectroscopy for material characterization.
Main Results:
- Successfully prepared amine-borane dimers and oligomers with diverse steric and electronic profiles.
- Demonstrated high catalytic efficiency in transfer hydrogenation, particularly with Lewis-paired oligomers and sterically hindered bis(amine-borane)s.
- Observed enhanced reactivity attributed to facilitated dissociation and H-bond assistance in oligomers.
- Confirmed structural similarity between materials from transfer dehydrogenation and thermal dehydrogenation via solid-state NMR.
Conclusions:
- Amine-borane oligomers represent a key intermediate class between molecular reductants and poly-amine-boranes.
- The developed synthetic strategy allows for tuning of amine-borane structures for optimized catalytic performance.
- These findings provide a comprehensive understanding of reactivity trends in amine-borane systems at varying molecular scales.
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