[1,4]Diazepines with [<i>B</i>]‐Fused Rings

Fryer, R. Ian; Walser, A.

doi:10.1002/9780470187371.ch4

Cited by 1 publication

(1 citation statement)

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“…Conversion of 18 to 19 is predicted to occur via a ring-flipping mechanism, although attempts to locate a transition state between 18 and the corresponding ring-flipped species Int3 were unsuccessful. However, the literature shows seven-membered heterocyclic rings have ring-flipping barriers in the range 40–60 kJ/mol. − The speices then has the proper orientation to undergo a [1,5]-hydride shift with a barrier of 113.1 kJ/mol to produce 19 . Similar suprafacial sigmatropic [1,5]-hydride shifts have been observed in 1,3-cycloheptadienes that have comparable calculated barriers (115.1 kJ/mol). , …”

Section: Results and Discussionmentioning

confidence: 99%

Reactions of Imines, Nitriles, and Isocyanides with Pentaphenylborole: Coordination, Ring Expansion, C–H Bond Activation, and Hydrogen Migration Reactions

et al. 2015

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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.

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