Synthesis of Circumpyrene by Alkyne Benzannulation of Brominated Dibenzo[,]ovalene.

A transition-metal catalyzed alkyne benzannulation allowed an unprecedented synthesis of circumpyrene, starting from 3,11-dibromo-6,14-dimesityldibenzo[,]ovalene (DBOV). The circumpyrene was characterized by a combination of NMR, mass spectrometry, and single-crystal X-ray diffraction analysis, revealing its multizigzag-edged structure. Two newly introduced C═C bonds in circumpyrene strongly perturbed the electronic structures of DBOV, as evidenced by increased optical and electrochemical energy gaps. This is in good agreement with an increased number of Clar's sextets as well as a decreased number of π-electrons in the conjugation pathway of circumpyrene, according to anisotropy of the induced current density (ACID) calculations. The present approach opens a new avenue to multizigzag-edged nanographenes and offers insights into their (opto)electronic properties.