Consecutively fused single‐, double‐, and triple‐expanded helicenes

Abstract We report the quantitative, chemoselective, and diastereospecific formation of defect‐free C‐shaped single S‐ M‐shaped consecutively fused double‐ triple‐expanded homochiral helicenes (all‐right ( P ) or all‐left M handed), in which two three expanded helicene subunits were exclusively together a helically winding manner, respectively, through trifluoroacetic acid‐promoted intramolecular multistep cascade alkyne benzannulations anthracene‐based cyclization precursors composed large number complicated dynamic stereoisomers due to axial chirality. The resulting racemic all separated into enantiomers by chiral chromatography showed intense circular dichroism circularly polarized luminescence (CPL) with absorption dissymmetry factors up 1.5 × 10 −2 0.94 , respectively. Moreover, highest CPL brightness (255 −1 ·cm among reported CPL‐active carbo‐ heterohelicenes ‐helicenoids. helicity inversion barriers remarkably increased increasing incorporated subunits, racemization was completely suppressed even at 80°C, providing first example an optically active static helical Key Points Defect‐free synthesis single‐, double‐, C‐, S‐, fully conjugated ladder structures, Quantitative chemoselective acid‐catalyzed cyclizations. Circularly configurationally stable pure helicenes.