Pd(II)-Catalyzed Regioselective Multiple C-H Arylations of 1-Naphthamides with Cyclic Diaryliodonium Salts: One-Step Access to [4]- and [5]Carbohelicenes.

Highly efficient and rapid construction of carbohelicenes is a desired but challenging task, especially starting from simple substrates. Herein, Pd(II)-catalyzed regioselective multiple C-H arylations of 1-naphthamides with cyclic diaryliodoniums have been accomplished for the first time, which enables facile one-step syntheses of [4]- and [5]carbohelicenes from readily available starting materials. The resulting single and double [4]carbohelicenes emit violet to deep-blue fluorescence; [4,5,4]-fused triple carbohelicenes exhibit sky-blue emissions, and phenoxazine-modified [4]carbohelicene shows a delayed fluorescence emission.