Reactions of imines, nitriles, and isocyanides with pentaphenylborole: coordination, ring expansion, C-H bond activation, and hydrogen migration reactions.
The reactions of pentaphenylborole with imines, isocyanides, and acetonitrile were investigated experimentally and theoretically. On the basis of literature precedent, we envisioned that the dipolar substrates would undergo facile ring expansion reactions to yield new BNC5 heterocycles. For acetonitrile and one particular imine, this ring expansion process was observed. However, in many cases, unexpected reactivity occurred. This included hydride migration of an imine ring expanded product and the ortho C-H bond activation of an aryl group of an imine if two phenyl groups were present on the α-carbon. A bulky group on the nitrogen atom of an imine prevented coordination to the boron center, and no reaction was observed, indicating that coordination to the borole is a critical step for any type of reaction to occur. Isocyanides made coordination complexes, but heating to induce further reactivity resulted in mixtures. The mechanisms were elucidated via DFT calculations, which complement the experimental findings.
Department of Chemistry and Biochemistry, Baylor University , One Bear Place #97348, Waco, Texas 76798, United States.
Kexuan
K
Huang
Department of Chemistry and Physics, La Trobe Institute for Molecular Science, La Trobe University , Melbourne, Victoria, Australia , 3086.
Shannon A
SA
Couchman
Department of Chemistry and Physics, La Trobe Institute for Molecular Science, La Trobe University , Melbourne, Victoria, Australia , 3086.
David J D
DJ
Wilson
Department of Chemistry and Physics, La Trobe Institute for Molecular Science, La Trobe University , Melbourne, Victoria, Australia , 3086.
Jason L
JL
Dutton
Department of Chemistry and Biochemistry, Baylor University , One Bear Place #97348, Waco, Texas 76798, United States.
Caleb D
CD
Martin