Synthesis of Stable Nanographenes with OBO-Doped Zigzag Edges Based on Tandem Demethylation-Electrophilic Borylation.

A tandem demethylation-aryl borylation strategy was developed to synthesize OBO-doped tetrabenzo[a,f,j,o]perylenes (namely "bistetracenes") and tetrabenzo[bc,ef,kl,no]coronenes (namely "peritetracenes"). The OBO-doped bistetracene analogues exhibited excellent stability and strong fluorescence, in contrast to the unstable all-carbon bistetracene. Single-crystal X-ray analysis for OBO-doped bistetracene revealed a twisted double [5]helicene structure, indicating that this synthesis is applicable to new heterohelicenes. Importantly, cyclodehydrogenation of the bistetracene analogues successfully produced the unprecedented heteroatom-doped peritetracenes, which opened up a new avenue to periacene-type nanographenes with stable zigzag edges.