Synthesis of Fluorescent 4‐Azapyrenes by Palladium(II)‐Catalyzed Dual C−H Bond Activation and Annulation

• Published in: Advanced synthesis & catalysis Vol. 363; no. 6; pp. 1695 - 1701
• Main Authors: Hsiao, Huan‐Chang, Annamalai, Pratheepkumar, Jayakumar, Jayachandran, Sun, Shang‐You, Chuang, Shih‐Ching
• Format: Journal Article
• Language: English
• Published: WEINHEIM Wiley 16.03.2021; Wiley Subscription Services, Inc
• Subjects: 4-azapyrene; Chemical reactions; Chemical synthesis; Chemistry; Chemistry, Applied; Chemistry, Organic; C−H activation; Dehydrogenation; Fluorescence; Hydrogen bonds; Organic chemistry; Palladium; palladium catalysis; phenanthrene; Physical Sciences; Rollover; Science & Technology; Substitutes; palladium catalysis; O-ARYLANILINES; CATALYSIS; MECHANISM; POLYCYCLIC AROMATIC-HYDROCARBONS; ALKYNES; phenanthrene; MULTIPLE; FUNCTIONALIZATION; C-H activation; fluorescence; PATHWAY; 4-azapyrene; EMISSION; DERIVATIVES
• ISSN: 1615-4150; 1615-4169
• DOI: 10.1002/adsc.202001404

Unique dual‐emissive and deep‐blue/green fluorescent multi‐substituted 4‐azapyrenes with bathochromic shift emission, quantum yields up to 0.60 and long excited‐state lifetime were synthesized successfully by annulative π‐extension reactions. This synthesis constitutes a palladium‐catalyzed dehydrogenative annulation of N‐acyl‐2‐aminobiaryls with in situ 1,3‐diynes as a key step, giving substituted phenanthrenes via a rollover C−H bond activation, followed by Bischler‐Napieralski cyclization. Further π‐extension by superacid‐mediated cyclization produced a blue fluorescent naphtho 4‐azapyrene.