Abstract
Aromatic hydrogenation is a challenging transformation typically requiring alkali or transition metal reagents and/or harsh conditions to facilitate the process. In sharp contrast, the aromatic heterocycle 2,4,6-tri-tert-butyl-1,3,5-triphosphabenzene is shown to be reduced under 4 atm of H-2 to give [3.1.0]bicylo reduction products, with the structure of the major isomer being confirmed by X-ray crystallography. NMR studies show this reaction proceeds via a reversible 1,4-H-2 addition to generate an intermediate species, which undergoes an irreversible suprafacial hydride shift concurrent with P P bond formation to give the isolated products. Further, para-hydrogen experiments confirmed the addition of H-2 to triphosphabenzene is a bimolecular process. Density functional theory (DFT) calculations show that facile distortion of the planar triphosphabenzene toward a boat-conformation provides a suprafacial combination of vacant acceptor and donor orbitals that permits this direct and uncatalyzed reduction of the aromatic molecule.
Original language | English |
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Pages (from-to) | 13453-13457 |
Number of pages | 5 |
Journal | Journal of the American Chemical Society |
Volume | 136 |
Issue number | 38 |
Early online date | 10 Sep 2014 |
DOIs | |
Publication status | Published - 24 Sep 2014 |
Structured keywords
- BCS and TECS CDTs
Keywords
- CATIONIC RHODIUM COMPLEXES
- MAIN-GROUP ELEMENTS
- HOMOGENEOUS HYDROGENATION
- SELECTIVE HYDROGENATION
- DIHYDROGEN COMPLEXES
- MOLECULAR-HYDROGEN
- ASYMMETRIC HYDROGENATION
- TRANSITION-METALS
- CATALYSTS
- OLEFINS