The synthesis of brominated-boron-doped PAHs by alkyne 1,1-bromoboration: Mechanistic and functionalisation studies

K. Yuan, R. J. Kahan, C. Si, A. Williams, S. Kirschner, M. Uzelac, E. Zysman-Colman, M. J. Ingleson

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34 Citations (SciVal)

Abstract

The synthesis of a range of brominated-Bn-containing (n = 1, 2) polycyclic aromatic hydrocarbons (PAHs) is achieved simply by reacting BBr3 with appropriately substituted alkynes via a bromoboration/electrophilic C-H borylation sequence. The brominated-Bn-PAHs were isolated as either the borinic acids or B-mesityl-protected derivatives, with the latter having extremely deep LUMOs for the B2-doped PAHs (with one example having a reduction potential of E1/2 = -0.96 V versus Fc+/Fc, Fc = ferrocene). Mechanistic studies revealed the reaction sequence proceeds by initial alkyne 1,1-bromoboration. 1,1-Bromoboration also was applied to access a number of unprecedented 1-bromo-2,2-diaryl substituted vinylboronate esters directly from internal alkynes. Bromoboration/C-H borylation installs useful C-Br units onto the Bn-PAHs, which were utilised in Negishi coupling reactions, including for the installation of two triarylamine donor (D) groups onto a B2-PAH. The resultant D-A-D molecule has a low optical gap with an absorption onset at 750 nm and emission centered at 810 nm in the solid state.

Original languageEnglish
Pages (from-to)3258-3267
Number of pages10
JournalChemical Science
Volume11
Issue number12
DOIs
Publication statusPublished - 28 Mar 2020

Bibliographical note

Funding Information:
The research leading to these results has received funding from the European Research Council under the Horizon 2020 Research and Innovation Program (Grant no. 769599), the Leverhulme Trust (RPG-2014-340) and the EPSRC (EP/P010482/ 1). C. Si thanks the China Scholarship Council (201806890001). Dr G. Nichol is thanked for the collection of X-ray diffraction data, Dr G. Whitehead for the structure of 2a and Dr A. Woodward for collecting photophysical data on compound 2c (see ESI‡).

Publisher Copyright:
This journal is © The Royal Society of Chemistry.

ASJC Scopus subject areas

  • Chemistry(all)

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