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The Thermal Rearrangement of an NHC-Ligated 3-Benzoborepin to an NHC-Boranorcaradiene |
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| Authors: | Masaki Shimoi Ilia Kevlishvili Takashi Watanabe Prof?Dr Katsuhiro Maeda Dr Steven J Geib Prof?Dr Dennis P Curran Prof?Dr Peng Liu Dr Tsuyoshi Taniguchi |
| Institution: | 1. Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa, 920-1192 Japan
These authors contributed equally to this work.;2. Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, 15260 USA These authors contributed equally to this work.;3. Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa, 920-1192 Japan;4. Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, 15260 USA |
| Abstract: | An N-heterocyclic-carbene-ligated 3-benzoborepin with a bridged structure has been synthesized by double radical trans-hydroboration of benzo3,4]cycloundec-3-ene-1,5-diyne with an N-heterocyclic carbene borane. The thermal reaction of the NHC-ligated borepin at 150 °C gives an isolable NHC-boranorcaradiene. Experiments and density functional theory calculations support a mechanism whereby the borepin initially rearranges to a boranorcaradiene by a thermal 6π-electrocyclic reaction. This is followed by 1,5-boron shift to give a rearranged boranorcaradiene. This shift occurs with stereoinversion at boron through a transition state with open-shell diradical character. This is the first example of the isolation of a boranorcaradiene from a thermal reaction of a borepin. |
| Keywords: | Bor Carbenliganden Elektrocyclische Reaktionen Hauptgruppenelemente Umlagerungen |