Hexamethylbenzene Elimination Enables the Generation of Transient, Sterically Unhindered Multiply Bonded Boron Species
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D5SC02645H.pdf
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Author(s)
Zhang, Chonghe
Dabringhaus, Philipp
Tra, Bi Youan E.
Gilliard, Robert J. Jr
Cummins, Christopher C.
Date Issued
May 16, 2025
Journal
Chemical Science
Publisher
Royal Society of Chemistry
Citation
Zhang, Chonghe, Dabringhaus, Philipp, Tra, Bi Youan E., Gilliard, Robert J. Jr and Cummins, Christopher C. 2025. "Hexamethylbenzene Elimination Enables the Generation of Transient, Sterically Unhindered Multiply Bonded Boron Species." Chemical Science, 16 (26).
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Final published version
Abstract
We present a method for the generation of boron-containing unsaturated small molecules via hexamethylbenzene elimination. The fragmentation precursors are obtained through bond insertion into phenyl boranorbornadiene (PhB(C6Me6), 1). Compound 1 undergoes 1,1-insertion with 2,6-xylyl isocyanide, affording a boron-doped bicyclo[2.2.2]octa-2,5-diene 2. Heating 2 in toluene results in the formation of a base-stabilized boraketenimine PhB(CNxyl)2 (i.e., borylene diisocyanide) as an intermediate via retro-Diels–Alder reaction. Surprisingly, PhB(CNxyl)2 dimerizes to give a boron-doped 6-membered ring (PhB)2C4(CNxyl)64. The reaction of 1 with trimethylamine N-oxide and phenyl azide yields triphenyl boroxine and a BN4 ring, respectively, implying the involvement of transient oxoborane (PhB[triple bond, length as m-dash]O) and iminoborane intermediates (PhB[triple bond, length as m-dash]NPh), respectively. Furthermore, boranorbornadiene also undergoes 2,3-insertion with mesityl isocyanate (MesNCO), affording a fused 6/5-membered heterocycle 11. This insertion profile is analogous to the insertion of phenyl azide into 1.
MIT Department
Massachusetts Institute of Technology. Department of Chemistry
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DOI of Published Version
https://doi.org/10.1039/D5SC02645H
