One-Pot Synthesis of Highly Emissive Dipyridinium Dihydrohelicenes

• Published in: Chemistry : a European journal Vol. 21; no. 19; pp. 7035 - 7038
• Main Authors: Santoro, Amedeo, Lord, Rianne M., Loughrey, Jonathan J., McGowan, Patrick C., Halcrow, Malcolm A., Henwood, Adam F., Thomson, Connor, Zysman-Colman, Eli
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 04.05.2015; WILEY‐VCH Verlag; Wiley; Wiley Subscription Services, Inc
• Subjects: Biotechnology; Cancer; Chemistry; Chemistry, Multidisciplinary; Condensing; Crystal structure; crystal structures; cytotoxicity; Derivatives; fluorescence; Helical; helical compounds; Hydrobromides; Physical Sciences; Science & Technology; Synthesis; voltammetry; helical compounds; voltammetry; fluorescence; STEREOSELECTIVE SYNTHESES; ONE HUNDRED YEARS; HELICENES; crystal structures; cytotoxicity; MOLECULES
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201406255

Condensation of a pyridyl‐2‐carbaldehyde derivative with 2‐(bromoethyl)amine hydrobromide gave tetracyclic pyrido[1,2‐a]pyrido[1′,2′:3,4]imidazo‐[2,1‐c]‐6,7‐dihydropyrazinium dications in excellent yields. Crystal structures and NOE data demonstrated the helical character of the dications, the dihedral angles between the two pyrido groups ranging from 28–45°. An intermediate in the synthesis was also characterized. A much brighter emission compared to literature helicenes has been found, with quantum yields as high as 60 % in the range of λ=460–600 nm. Preliminary cytotoxicity studies against HT‐29 cancer cells demonstrated moderate‐to‐good activity, with IC50 values 12–30× that of cisplatin. Helical compounds: Condensation of a pyridyl‐2‐carbaldehyde derivative with 2‐(bromoethyl)amine hydrobromide gave tetracyclic pyrido[1,2‐a]pyrido[1′,2′:3,4]imidazo‐[2,1‐c]‐6,7‐dihydropyrazinium dications in excellent yields. These afford unusually bright emissions for helicene‐like compounds, with ΦPL as high as 59.9 % in the range of λ=460–600 nm. Preliminary cytotoxicity studies against the HT‐29 cancer cell line demonstrated moderate‐to‐good activity, with inhibitor concentration (IC50) values 12–30× that of cisplatin (see scheme).