title: Functionalization of quinoxalines by using TMP bases: preparation of tetracyclic heterocycles with high photoluminescene quantum yields.
abstract: 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, (BrCl2 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.
authors.affiliation: Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13, Haus F, 81377 München (Germany).
authors.forename: Julia
authors.initials: J
authors.lastname: Nafe
authors.forename: Simon
authors.initials: S
authors.lastname: Herbert
authors.forename: Florian
authors.initials: F
authors.lastname: Auras
authors.forename: Konstantin
authors.initials: K
authors.lastname: Karaghiosoff
authors.forename: Thomas
authors.initials: T
authors.lastname: Bein
authors.forename: Paul
authors.initials: P
authors.lastname: Knochel
mesh_terms: D006571:Heterocyclic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D007700:Kinetics; D008163:Luminescent Measurements; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000737:chemistry; D010880:Piperidines / Q000737:chemistry; D011789:Quantum Theory; D011810:Quinoxalines / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D006571:Heterocyclic Compounds; D009942:Organometallic Compounds; D010880:Piperidines; D011810:Quinoxalines; C530465:TMPMgCl.LiCl; C551336:2,2,6,6-tetramethylpiperidide
keywords: anellation; fluorescence; functionalization; metalation; photoluminescence; quantum yield