2,2′-Dilithiobiphenyl by direct lithiation of biphenylene

The reaction of biphenylene (1) with an excess of lithium powder (1:14 molar ratio) and a catalytic amount of DTBB (10 mol %) in THF at room temperature leads to the formation of the dilithiated species I by reductive opening of the four-membered ring. Further reaction of this intermediate with different electrophiles [Electrophile = H2O, D2O, Me3SiCl, t-BuCHO, Et2CO, n-Pr2CO, (CH2)5CO, Ph2CO and adamantanone] at 0 °C yields the corresponding products 2, after hydrolysis with water. Cyclisation of some representative examples of compounds 2 with H3PO4 gives the corresponding dibenzoxepines 3.