Chromium-Mediated Synthesis of Polycyclic Aromatic Compounds from Halobiaryls

Reaction of 2,2‘-dihalobiphenyl with butyllithium followed by the addition of chromium(III) chloride and alkynes afforded the corresponding phenanthrene derivatives via formal [4 + 2] cycloaddition. A variety of alkynes could be used for this reaction, such as alkyl, aryl, silyl, and alkoxycarbonyl alkynes. Repetitive process of the reaction gave more extended polycyclic compounds such as benzo[<i>g</i>]chrysene and azacyclopentaphenalene derivatives.