A Biradical Cylization Route to Axially Chiral Biheteroaryls

Significance

Reported is the synthesis of axially chiral bis(benzocarbazoles) 3 and bis(quinindolines) 4 via two independent biradical cyclizations from bis(ketenimines) 1 and bis(carbodiimides) 2, which in turn are derived from the 1,4-diphenyl-1,3-butadiynes.The preparation of mixed bi­hetero­aryls, consisting of benzocarbazole and quinindoline units, is also reported with a slightly modified strategy. The scope of this interesting multibond-forming reaction was poorly investigated. A mechanism for cyclization is proposed involving biradical intermediate A.