title: When Indolizine Meets Quinoline: Diversity-Oriented Synthesis of New Polyheterocycles and Their Optical Properties.
abstract: Fluorescence-based technologies play a pivotal role in various biomedical applications. Here we report an efficient route to a new class of fluorophores, indolizino[3,2-c]quinolines, via the oxidative Pictet-Spengler cyclization strategy. The condensation of several 2-methylpyridines with 2-bromo-2'-nitroacetophenone allowed for the rapid assembly of indolizines with a 2-nitrophenyl group at the C2 position. The subsequent reduction of the nitro group under mild conditions followed by oxidative Pictet-Spengler cyclization with various aryl aldehydes in the presence of a catalytic amount of FeCl3 furnished the indolizino[3,2-c]quinolines in good overall yields. We also examined the photophysical properties of this new series of polyheterocyclic compounds. Several indolizino[3,2-c]quinolines were found to have unique and desirable optical properties, suggesting that these compounds may be suitable for use as prospective fluorescent probes in aqueous systems.
authors.affiliation: †College of Pharmacy and Yonsei Institute of Pharmaceutical Sciences, Yonsei University 85 Songdogwahak-ro, Yeonsu-gu, Incheon 406-840, Republic of Korea.
authors.forename: Sujin
authors.initials: S
authors.lastname: Park
authors.affiliation: ‡College of Pharmacy, Research Institute of Pharmaceutical Sciences, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 151-742, Republic of Korea.
authors.forename: Dah In
authors.initials: DI
authors.lastname: Kwon
authors.affiliation: ‡College of Pharmacy, Research Institute of Pharmaceutical Sciences, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 151-742, Republic of Korea.
authors.forename: Jeeyeon
authors.initials: J
authors.lastname: Lee
authors.affiliation: †College of Pharmacy and Yonsei Institute of Pharmaceutical Sciences, Yonsei University 85 Songdogwahak-ro, Yeonsu-gu, Incheon 406-840, Republic of Korea.
authors.forename: Ikyon
authors.initials: I
authors.lastname: Kim
mesh_terms: D018360:Crystallography, X-Ray; D003500:Cyclization; D006571:Heterocyclic Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D007212:Indolizines / Q000138:chemical synthesis* / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D055620:Optical Phenomena; D010847:Picolines / Q000737:chemistry; D011804:Quinolines / Q000138:chemical synthesis* / Q000737:chemistry; D013050:Spectrometry, Fluorescence
chemical_list: D006571:Heterocyclic Compounds; D007212:Indolizines; D010847:Picolines; D011804:Quinolines; C530793:2-picoline
keywords: Pictet−Spengler cyclization; fluorescence-based technologies; indolizine; polyheterocycles; quinoline