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Reversible Boron-Insertion into Aromatic C-C Bonds
Kaito Kuroki1, Tatsuyoshi Ito1, Jun Takaya1
1Department of Chemistry, School of Science, Tokyo Institute of Technology O-okayama, Meguro-ku, Tokyo, 152-8551, Japan.
Abstract:
Formation of borabicyclo[3.2.0]heptadiene derivatives was achieved via boron-insertion into aromatic C-C bonds in the photo-promoted skeletal rearrangement reaction of triarylboranes bearing an ortho-phosphino substituent (ambiphilic phosphine-boranes). The borabicyclo[3.2.0]heptadiene derivatives were fully characterized by NMR and X-ray analyses. The dearomatized products were demonstrated to undergo the reverse reaction in the dark at room temperature, realizing photochemical and thermal interconversion between triarylboranes and boron-doped bicyclic systems. Experimental and theoretical studies revealed that sequential two electrocyclic reactions involving E/Z-isomerization of an alkene moiety proceed via a highly strained trans-borepin intermediate.
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