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Metal-free alkyne annulation enabling π-extension of boron-doped polycyclic aromatic hydrocarbons.

Mandala AnithaTo-Jen ChinGuan-Cheng LiuChi-Tien HsiehKuan-Hua WangShu-Li LiMu-Jeng ChengJeffrey M Farrell
Published in: Chemical science (2024)
A C-H functionalizing annulation reaction of boron-doped polycyclic aromatic hydrocarbons (PAHs) with alkynes is described. This metal-free π-extension provides a new synthetic route to fusion atom B-doped polycyclic aromatic hydrocarbons (PAHs) that is demonstrated with the synthesis of a family of new, functionalized, structurally constrained 6a,15a-diborabenzo[ tuv ]naphtho[2,1- b ]picenes. These annulation products exhibit deep LUMO energy levels, strong visible-range absorptions, and sterically accessible π-systems that can adopt herringbone or π-stacked solid-state structures based on choice of substituents. From regioselectivity and DFT calculations, we propose an annulation mechanism involving intramolecular electrophilic aromatic substitution of a zwitterionic intermediate.
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