Switching the Statistical C3 /C1 Ratio in the Threefold Aromatic Substitution of Tribenzotriquinacenes towards the C3 Isomer.

Abstract

Tribenzotriquinacene (TBTQ) is a bowl-shaped molecule that has been widely used as a molecular building block in supramolecular and materials chemistry. Especially C3 -symmetric threefold-substituted TBTQs are interesting for these purposes. Until now a general and selective synthetic approach to those C3 -symmetric products was lacking, mainly because the typically used electrophilic aromatic substitution reactions of the parent TBTQ hydrocarbons produce predominantly the C1 isomer over the C3 isomer (3:1 statistical ratio). Herein we introduce a threefold borylation of TBTQ with the C3 isomer as the main product (2.6:1 C3 /C1 ratio). The borylated TBTQ can be converted in good yields into other C3 -symmetric TBTQs, thus allowing straightforward synthetic access to new building blocks for supramolecular and materials chemistry.