Fraternal twins: B(2)O(2)- or B(2)N(2)-doped polycyclic π systems and their formation mechanism via regiodivergent Au- versus amine-catalyzed cyclizations.

BE-doped polycyclic aromatic hydrocarbons PAHs; E = NR, O often exhibit superior optoelectronic properties compared to their carbonaceous congeners. Herein, we report an efficient and convenient synthetic route to this compound class, based on the intramolecular addition of aryl(Mes)BE-H bonds to -positioned butadiyne substituents. The reactions can proceed either under Au(I) or NEt catalysis, with the same substrate giving rise to distinct addition patterns. Treatment of -MesB(OH)-diphenylbutadiyne or ,'-bis[MesB(OH)]-diphenylbutadiyne with [Au(PPh)(NTf)] furnishes an ethynyl-substituted BO-naphthalene or a (BO)-binaphthyl (B2O2; 2,3-OC-addition), respectively. In contrast, NEt-catalyzed double cyclization of ,'-bis[MesB(OH)]-diphenylbutadiyne affords the corresponding (BO)-naphthylbenzofulvene (-B2O2; 1,3-OC-addition). Replacement of NEt with ethylenediamine generates the analogous (BN)-doped PAH (-B2N2). Notably, both B2O2 and -B2N2 show high photoluminescence quantum yields of = 80% and 93%, respectively. Using the formation of -B2O2 as a model reaction, a plausible mechanistic scenario was elucidated through quantum-chemical calculations and systematic probe experiments, providing further novel BE-doped PAHs.