Intramolecular Borylation via Sequential B‐Mes Bond Cleavage for the Divergent Synthesis of B,N,B‐doped Benzo[4]helicenes

Abstract

New symmetric and unsymmetric B,N,B‐doped benzo[4]helicenes 3 ‐ 6a/b have been achieved in good yields, using a three‐step process, starting from N(tolyl) 3 in a highly divergent manner (7 examples). A borinic acid functionalized 1,4‐B,N‐anthracene 1 was found to display unprecedented reactivity, acting as a convenient and highly effective precursor for selective formation of bromo substituted B,N,B‐benzo[4]helicenes 2a / 2b via intramolecular borylation and sequential B‐Mes bond cleavage in presence of BBr 3 . Subsequent reaction of 2a / 2b with Ar‐Li provided a highly effective toolbox for the preparation of symmetrically/unsymmetrically functionalized B,N,B‐helicenes. Their high photoluminescence quantum yields along with the small Δ E ST suggest the potential as thermally activated delayed fluorescence (TADF) emitters for organic light‐emitting diodes (OLEDs).