Facile Two‐Step Synthesis of 1,10‐Phenanthroline‐Derived Polyaza[7]helicenes with High Fluorescence and CPL Efficiency

Abstract

A facile two-step synthesis of aza[7]helicenes possessing a 6-5-6-6-6-5-6 skeleton from commercially available 2,9-dichloro-1,10-phenanthroline via double amination with aniline derivatives followed by hypervalent iodine reagent-mediated intramolecular double-NH/CH couplings was developed. Single-crystal X-ray analyses of the helicenes revealed unique structures, including both a significantly twisted center and planar terminals of the skeleton. The azahelicenes show high fluorescent quantum yields (Φs) under both neutral (Φ: 0.25-0.55) and acidic conditions (Φ: up to 0.80). An enantiomerically pure aza[7]helicene showed high circularly polarized luminescence (CPL) activity under both neutral and acidic conditions (g : up to 0.009).

Azabora[5]helicene Charge‐Transfer Dyes Show Efficient and Spectrally Variable Circularly Polarized Luminescence

“…Potential applications are chiral sensing or the preparation of chiroptical systems with innovative photophysical design . Helicenes belong to the most frequently reported CPL‐SOM architectures, among them carbo[ n ]helicenes, helicenes that incorporate heteroatoms (azahelicenes, oxahelicenes, thiahelicenes), and metallahelicenes …”

6‐Arylamino‐2,2′‐bipyridine “Push‐Pull” Fluorophores: Solvent‐Free Synthesis and Photophysical Studies

“…So far the syntheses of aniline‐(benzo)bipyridines is not well explored, and the most common synthetic approaches towards such heterocycles are based on the nucleophilic substitution of leaving groups (triflate group or chlorine atom(s)), cross‐coupling reactions in bromo‐pyridines or some hetrocyclization reactions (Scheme ). Thus, the substitution of both chlorine atoms in 2,9‐dichloro‐1,10‐phenanthroline under the reaction of anilines under neat conditions was reported recently . Additionally, the nucleophilic substitution of triflate group or chlorine atom by the aniline residues (in particular, under solvent‐free conditions at the α‐position of phenanthroline,) have been reported.…”

“…2,2′‐Bipyridines and their annulated analogs are the most commonly used ligands for the transition metal cations, including platinum and copper . Additionally, 2,2′‐bipyridines bearing the aromatic amines residues in the α‐position of the pyridine moiety (moieties) could be further transformed to afford fused polynuclear systems ,. In medicinal chemistry, some aniline‐substituted 2,2′‐bipyridines are reported as kinase and COX‐2 inhibitors (Figure ).…”

Synthesis of Benzofuranones via Malonates Desymmetrization: Yield Increase by the Portion‐wise Addition of Quinones

“…With our surprise and delight, the yield of the reaction increased from 9 to 82 % at −20 °C, (compare entries 11 and 13) and rose up to 70 % (entries 14 and 15) with high enantioselectivity at +4 °C. The portion‐wise addition is a known procedure in chemistry, but these results were exciting. We investigated the effect of the addition of malonate 1 a in different portion sizes (Table ).…”