The synthesis of brominated-boron-doped PAHs by alkyne 1,1-bromoboration : mechanistic and functionalisation studies
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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 acid 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 direct 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.
Ingleson , M J , Yuan , K , Kahan , R J , Si , C , Williams , A , Kirschner , S , Uzelac , M , Zysman-Colman , E & Ingleson , M J 2020 , ' The synthesis of brominated-boron-doped PAHs by alkyne 1,1-bromoboration : mechanistic and functionalisation studies ' , Chemical Science , vol. Advance Article . https://doi.org/10.1039/C9SC05404A
Copyright © 2020 The Author(s). Open Access Article. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.
DescriptionThe 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).
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