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Functionalization of Quinoxalines by Using TMP Bases: Preparation of Tetracyclic Heterocycles with High Photoluminescene Quantum Yields
Author(s) -
Nafe Julia,
Herbert Simon,
Auras Florian,
Karaghiosoff Konstantin,
Bein Thomas,
Knochel Paul
Publication year - 2015
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201405240
Subject(s) - electrophile , chemistry , photoluminescence , surface modification , regioselectivity , iodide , allylic rearrangement , aryl , bromide , quenching (fluorescence) , fluorescence , photochemistry , absorption (acoustics) , combinatorial chemistry , organic chemistry , materials science , catalysis , alkyl , physics , optoelectronics , quantum mechanics , composite material
Tetracyclic heterocycles that exhibit high photoluminescence quantum yields were synthesized by anellation reactions of mono‐, di‐, and trifunctionalized 2,3‐dichloroquinoxalines. Thus, treatment of 2,3‐dichloroquinoxaline with TMPLi (TMP=2,2,6,6‐tetramethylpiperidyl) allows a regioselective lithiation in position 5. Quenching with various electrophiles (iodine, (BrCl 2 C) 2 , allylic bromide, acid chloride, aryl iodide) leads to 5‐functionalized 2,3‐dichloroquinoxalines. Further functionalization in positions 6 and 8 can be achieved by using TMPLi or TMPMgCl ⋅ LiCl furnishing a range of new di‐ and tri‐functionalized 2,3‐dichloroquinoxalines. The chlorine atoms are readily substituted by anellation with 1,2‐diphenols or 1,2‐dithiophenols leading to a series of new tetracyclic compounds. These materials exhibit strong, tunable optical absorption and emission in the blue and green spectral region. The substituted O‐heterocyclic compounds exhibit particularly high photoluminescence quantum yields of up to 90 %, which renders them interesting candidates for fluorescence imaging applications.