Pd-Catalyzed Dual C–H Activation/Cyclization: Convergent and Divergent Synthesis of 1‑Azahelicenes

• Published in: Organic letters 2024-10, Vol.26 (42), p.9005-9010
• Main Authors: Xu, Yi-Xin, Liang, Yu-Qing, Liu, Wei-Ming, Fang, Hui-Kang, Li, Hong-Kun, Ji, Shun-Jun, Cai, Zhong-Jian
• Format: Article
• Language: English
• ISSN: 1523-7060; 1523-7052; 1523-7052
• DOI: 10.1021/acs.orglett.4c03136

Herein, we report a convergent synthesis of 1-azahelicenes using easily available quinoline derivatives and cyclic diaryliodonium salts as starting materials. This reaction undergoes a palladium-catalyzed dual C–H activation/cyclization process to give facile access to a wide range of 1-aza[5]­helicenes and 1-aza[6]­helicenes with abundant functional groups (including F, Cl, Br, I, CF3, SeR, SR, and heteroaryl) in moderate to excellent yields, thereby providing new opportunities to fine-tune the properties of the helicene backbone. In addition, the obtained products could be further transformed into helicene-based Lewis base catalysts and redox switch materials easily. Notably, one selected 1-azahelicene shined bright yellow light by aggregation. These features enlarge the chemical space of 1-azahelicenes and inspire further utilization in other areas of research.