Copper-Catalyzed Aerobic Oxidative Dicarbonylation of Indoles toward Solvatochromic Fluorescent Indole-Substituted Quinoxalines

Synthesis of Ynones via N-Iodosuccinimide-Mediated Oxidation of Propargyl Alcohols under Mild Conditions

A convenient and mild approach for the construction of ynones via N-iodosuccinimide (NIS)-mediated oxidation of propargyl alcohols has been described. This reaction could furnish the ynone products with a diversity of functional groups in moderate to excellent yields, and the flexibility of this method was demonstrated by the gram-scale experiment and further transformation.

Multicomponent Assembly of Trisubstituted Imidazoles and Their Photochemical Cyclization into Fused Polyheterocyclic Scaffolds

A straightforward route to a large and diverse library of trisubstituted imidazoles was established via a three-component reaction of 2-oxoaldehydes, 1,3-dicarbonyl compounds, and acyclic nitrogen bis-nucleophiles. The obtained products were subsequently explored in a photochemical cyclization yielding a variety of imidazole-fused polycyclic compounds.

Dehydrogenative Aza-[4 + 2] Cycloaddition of Amines with 1,3-Dienes via Dual Catalysis

We describe a synergistic utilization of copper catalysis and proton-transfer catalysis that enables an atom- and step-economical aza-[4 + 2] cycloaddition reaction of readily available N-arylamino carbonyl compounds with simple 1,3-dienes. The reaction proceeds smoothly under an air atmosphere and produces water as the sole side product. Whereas the amines can directly serve as the C- and N-atom donors, this operationally simple protocol provides green, rapid, and efficient access to 1,2,3,6-tetrahydropyridines with a broad scope.

Cu2+ -selective naked-eye 'off-on' fluorescent probe with multisignals: chromaticity, fluorescence, electrochemistry

In this study, a rhodamine-acetylferrocene conjugate of RBFc was synthesized and then characterized using spectroscopy and single-crystal analysis. The chemosensor RBFc exhibited a marked colour change from colourless to pink after binding to Cu²⁺ ions. Importantly, under the presence of the other competing cations in aqueous solution, only Cu²⁺ ions caused spirolactam ring opening in rhodamine B in RBFc, resulting in an enhanced absorbance of ultraviolet light spectra and fluorescence spectra, as well as obvious shifts in cyclic voltammetry curves and differential pulsed voltammetry curves. The novel probe described in this manuscript provides an attractive approach for detecting Cu²⁺ in the presence of other multisignals.

Regioselective N-1 and C-2 diacylation of 3-substituted indoles with arylglyoxal hydrates for the synthesis of indolyl diketones

A highly regioselective N-1 and C-2 diacylation of 3-substituted indoles with arylglyoxal hydrates to afford N-1 and C-2 indolyl diketones in moderate to good yields is described. Notably, the control of regioselectivity is achieved by small changes in the Cu catalyst, additive and solvent. Importantly, the intermediates for N-1 and C-2 diacylation were detected and two plausible pathways were also proposed.

Cu/Pd-Catalyzed chemoselective synthesis of C-3 dicarbonyl indoles and bis(indolyl)alkanes from aldehydes and indoles

A novel Cu/Pd-catalyzed chemoselective synthesis of C-3 dicarbonyl indoles and bis(indolyl)alkanes from aldehydes and indoles has been achieved, which has good substrate universality and high efficacy on large-scale.

Three-Component Activation/Alkynylation/Cyclocondensation (AACC) Synthesis of Enhanced Emission Solvatochromic 3-Ethynylquinoxalines

2-Substituted 3-ethynylquinoxaline chromophores can be readily synthesized by a consecutive activation-alkynylation-cyclocondensation (AACC) one-pot sequence in a three-component manner. In comparison with the previously published four-component glyoxylation starting from electron-rich π-nucleophiles, the direct activation of (hetero)aryl glyoxylic acids allows the introduction of substituents that cannot be directly accessed by glyoxylation. By introducing N,N-dimethylaniline as a strong donor in the 2-position, the emission solvatochromicity of 3-ethynylquinoxalines can be considerably enhanced to cover the spectral range from blue-green to deep red-orange with a single chromophore in a relatively narrow polarity window. The diversity-oriented nature of the synthetic multicomponent reaction concept enables comprehensive investigations of structure-property relationships by Hammett correlations and Lippert-Mataga analysis, as well as the elucidation of the electronic structure of the emission solvatochromic π-conjugated donor-acceptor systems by DFT and time-dependent DFT calculations with the PBEh1PBE functional for a better reproduction of the dominant charge-transfer character of the longest wavelength absorption band.

Copper-catalyzed synthesis of indolyl diketones via C–H oxidation/diacylation of indoles with arylglyoxal hydrates

Copper-catalyzed synthesis of indolyl diketonesviaC–H oxidation/diacylation of indoles with arylglyoxal hydrates is described.

The dicarbonylation of indoles via Friedel–Crafts reaction with dicarbonyl nitrile generated in situ and retro-cyanohydrination

The reaction of indole and β-carbonyl nitrile to generate dicarbonyl indoles has been developed. This process involves α-oxonation of the β-carbonyl nitrile, Friedel–Crafts reaction with indoles and retro-cyanohydrination form dicarbonyl indoles.