The cyclic trimer of dibenzofuran linked at the 4,6-positions, named cyclo-4,6-dibenzofuranylene, was synthesized by Ni(0)-mediated reductive coupling of 4,6-dibromodibenzofuran. DFT calculation indicated that the flake-shaped C2 symmetric structure is the most stable conformer and the propeller-shaped D3 symmetric structure is the minor conformer with a higher energy (+19.1 kcal mol-1). The calculated inversion energy of the C2 conformer through a Cs symmetric transition state was +4.1 kcal mol-1, showing rapid fluctuation, which is consistent with the observation of only one set of 1HNMR signals of dibenzofuran of cyclo-4,6-dibenzofuranylene.
- Cyclic trimer
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