Nickel-Catalyzed N,N-Diarylation of 8-Aminoquinoline with Large Steric Aryl Bromides and Fluorescence of Products

5-Aminopyrazole Dimerization: Cu-Promoted Switchable Synthesis of Pyrazole-Fused Pyridazines and Pyrazines via Direct Coupling of C-H/N-H, C-H/C-H, and N-H/N-H Bonds

A Cu-promoted highly chemoselective dimerization of 5-aminopyrazoles to produce pyrazole-fused pyridazines and pyrazines is reported. The protocol generates switchable products via the direct coupling of C-H/N-H, C-H/C-H and N-H/N-H bonds, with the merits of broad substrate scope and high functional group compatibility. Gram-scale experiments demonstrated the potential applications of this reaction. Moreover, the preliminary fluorescence results uncovered that dipyrazole-fused pyridazines and pyrazines may have some potential applications in materials chemistry.

General (hetero)polyaryl amine synthesis via multicomponent cycloaromatization of amines

(Hetero)polyaryl amines are extensively prevalent in pharmaceuticals, fine chemicals, and materials but the intricate and varied nature of their structures severely restricts their synthesis. Here, we present a selective multicomponent cycloaromatization of structurally and functionally diverse amine substrates for the general and modular synthesis of (hetero)polyaryl amines through copper(I)-catalysis. This strategy directly constructs a remarkable range of amino group-functionalized (hetero)polyaryl frameworks (194 examples), including naphthalene, binaphthalene, phenanthren, benzothiophene, dibenzothiophene, benzofuran, dibenzofuran, quinoline, isoquinoline, quinazoline, and others, which are challenging or impossible to obtain using alternative methods. Copper(III)-acetylide species are involved in driving the exclusive 7-endo-dig cyclization, suppressing many side-reactions that are susceptible to occur. Due to the easy introduction of various functional units into heteropolyarylamines, multiple functionalized fluorescent dyes can be arbitrarily synthesized, which can serve as effective fluorescent probes for monitoring the pathological processes (e.g. chemotherapy-induced cell apoptosis) and studying the related disease mechanisms.

π-π conjugated PDI supramolecular regulating the photoluminescence of imine-COFs for sensitive smartphone visual detection of levofloxacin

As the contamination and enrichment in food chain of levofloxacin (LV) antibiotics have caused a significant threat to life safety, the instant detection of LV has become an urgent need. Here, a PDI-functionalized imine-based covalent organic framework (PDI-COF300) was prepared by the electrostatic self-assembly method as fluorescent probe for smartphone visual detection of LV, which exhibited excellent fluorescence quantum yield (82.68%), greater stability, high sensitivity with detection limit of 0.303 μM. Based on the results of molecular docking and Stern-Volmer equation, the LV detection by PDI-COF300 was mainly a static quenching process through π-π stacked hydrophobic interactions and fluorescence resonance energy transfer. Besides, PDI-COF300 was applied to LV detection in environmental medium and milk samples with recoveries from 85.56% to 108.34% and relative standard deviations <2.70%. This work also provided a new general strategy for using PDI-COF in smartphone devices and fluorescent papers for LV fluorescence detection and microanalysis.

Oxidative cross-coupling of quinoxalinones with indoles enabled by acidochromism

An oxidative cross-coupling of quinoxalinones with indole derivatives via B(C₆F₅)₃·H₂O induced acidochromism of quinoxalinone derivatives was developed under mild and external photocatalyst-free conditions. The reaction shows excellent substrate scope, accommodating a wide range of functional groups. The usefulness of this strategy was demonstrated by the synthesis of the natural products Azacephalandole A and Cephalandole A in high yields. Moreover, the products are fluorophores showing prevalent fluorescence properties with a wide emission range and good relative quantum yields.

Cage-Confinement Induced Emission Enhancement

As a proof-of-concept study, Imi-cage and Phos-cage organic molecular cages (OMCs) containing the triphenylphosphine (TPP) moiety, a nonclassic AIE luminogen (AIEgen), have been designed to demonstrate the cage-confinement induced emission enhancement (CCIEE). Thanks to the confinement effect of OMCs, the rigid Imi-cage exhibits much higher photoluminescence (PL) quantum yield (Φ_PL) than the open-shell Semicage and small molecule TPP in both solution and amorphous solid states. The emission of Phos-cage could be further enhanced in crystalline solid state with a remarkably high Φ_PL of 97.6% (vs 3.47% of crystalline TPP) benefiting from AIE enabled by the highly ordered molecular packing. The novel strategy of CCIEE via confining an AIEgen into an OMC to achieve a significant emission enhancement will shed light on the development of solid-state highly fluorescent materials. The fluorescent nature of Imi-cage was further exploited for the ultrahighly sensitive detection of the explosive picric acid.