Aluminium-mediated aromatic C-F bond activation: regioswitchable construction of benzene-fused triphenylene frameworks

Selective synthesis of benzo[f] tetraphenes or benzo[g] chrysenes was achieved via aromatic C-F bond cleavage and unprecedented regioselective C-C bond formation depending upon the choice of aluminium reagents. On treatment with AlCl3, 2-(biphenyl-2-yl)-1fluoronaphthalenes afforded exclusively benzo[f] tetraphenes via C-C bond formation on the carbon atom gamma to the original position of the fluorine substituent. In contrast, alpha-selective C-C bond formation was promoted by treatment with gamma-Al2O3 to give benzo[g] chrysenes.