Bis(heterocumulenes) Derived from the 1,4-Diphenyl-1,3-butadiyne Framework. Synthesis of Three New Classes of Axially Chiral Biheteroaryls

Bis(ketenimines) and bis(carbodiimides) derived from 1,4-bis(2-aminophenyl)-1,3-butadiynes via two independent biradical cyclizations provided, respectively, axially chiral
bis(benzocarbazoles) and bis(quinindolines). Mixed biheteroaryls, consisting of benzocarbazole and quinindoline units,
have been also prepared by a slightly modified strategy.