Hydroboration of imines: intermolecular vs. intramolecular hydride transfer
A crucial step in the formation of mono-aminoboranes (R 2 N–BH 2 ) from the corresponding imine–BH 3 adducts, under mild reaction conditions, is the 1,3-hydride shift. We offer experimental and theoretical insights into this molecular rearrangement according to two mechanistic pathways: intra-molecu...
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Veröffentlicht in: | New journal of chemistry 2023-06, Vol.47 (24), p.11544-11556 |
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Hauptverfasser: | , , |
Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | A crucial step in the formation of mono-aminoboranes (R
2
N–BH
2
) from the corresponding imine–BH
3
adducts, under mild reaction conditions, is the 1,3-hydride shift. We offer experimental and theoretical insights into this molecular rearrangement according to two mechanistic pathways: intra-molecular (unimolecular) and inter-molecular (bimolecular). Even though a few experimental observations were inconclusive, an isotope-based experiment suggested that the 1,3-hydride shift occurs bimolecularly. In addition, the shape of the potential energy landscape, generated
via
the computational means, strongly suggests that these reactions are bimolecular. Relative energy gradient analysis enabled to identify the driving forces according to both scenarios and to explain the unusual shape of the minimum energy path in a unimolecular process. Our results imply that elevated temperature (60 °C) supplies the reactants with sufficient energy to cross the barrier, whereby each collision with properly oriented reactants results in mono-aminoborane formation. |
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ISSN: | 1144-0546 1369-9261 |
DOI: | 10.1039/D3NJ01979A |