ICl/AgNO3 Co-Catalyzed Radical Oxidation of Diaryl- and Alkylarylalkynes into 1,2-Diketones

Iodine-Catalyzed Room-Temperature Aerobic Oxidation of C(sp3)-H Bonds and Its Application in the Synthesis of Quinoxaline Derivatives

An iodine-catalyzed aerobic oxidation reaction of C(sp3)-H bonds was established at room temperature. In this transformation, iodine acts as a Lewis acid catalyst, and the pyridine moiety in the substrate plays a crucial role. Under the optimum reaction conditions, picolyl ketone substrates were smoothly transformed into the corresponding 1,2-dicarbonyl compounds, and the subsequent introduction of 1,2-diaminobenzenes into the reaction mixture led to the formation of various quinoxaline derivatives. This synthetic process does not use transition metals and also features mild reaction conditions, operational simplicity, and gram-scale synthesis.

A 1,2-Aryl Migration Reaction in Visible-Light-Mediated Synthesis of Quinoxaline Derivatives: Mechanistic Studies

The synthesis of quinoxaline derivatives holds critical importance in various fields ranging from pharmaceuticals to material science. In this study, we introduce a practical light-mediated method for the efficient synthesis of quinoxaline derivatives. This approach enabled the sequential two-step, one-pot synthesis of 1,2-dihydro-2,2-diaryl-substituted quinoxalines from quinones, alkynes, and diamines. By adjusting the stoichiometric ratios and reaction conditions, the method was shifted to yield 2,3-diaryl-substituted quinoxalines exclusively, demonstrating remarkable versatility and efficiency. This switch in reaction outcomes was revealed to involve an oxidative 1,2-aryl migration through a combination of thorough experimental and computational mechanistic studies.

Synthesis of Indolyl Phenyl Diketones through Visible-Light-Promoted Ni-Catalyzed Intramolecular Cyclization/Oxidation Sequence of Ynones

The combination of visible light catalysis and Ni catalysis has enabled the synthesis of indolyl phenyl diketones through the cyclization/oxidation process of ynones. This reaction proceeded under mild and base-free conditions and showed a broad scope and feasibility for gram-scale synthesis. Several natural products and biologically interesting molecules could be readily postfunctionalized by this method.

AgNO3 as Nitrogen Source for Cu-Catalyzed Cyclization of Oximes with Isocyanates: A Facile Route to N-2-Aryl-1,2,3-triazoles

A versatile copper-catalyzed [3 + 1 + 1] annulation of oximes and isocyanates with AgNO₃ is described. In this conversion, AgNO₃ and isocyanates instead of conventional azide or diazonium reagents were used as the nitrogen source. This three-component transformation was achieved by cleaving N-O/C-H/C-N bonds and building C═N/N-N bonds, which provides a strategy to prepare N-2-aryl-1,2,3-triazoles with a good substrate and functional compatibility.

Total Synthesis of Nortopsentin D via a Late-Stage Pinacol-like Rearrangement

Nortopsentin D is part of a class of bis(indole) alkaloids known for their biological activity, including inhibitory activity in tumoral cells and antifungal activity. Herein we describe the first total synthesis of nortopsentin D, in which amidine and dione undergo a pivotal condensation and subsequent cyclization via a pinacol-like rearrangement. This synthesis represents a unique strategy for the formation of 5,5-disubstituted (4H)-imidazol-4-one containing natural products, many of which have yet to succumb to total synthesis.

Visible-Light-Induced Photocatalytic Oxidative Decarboxylation of Cinnamic Acids to 1,2-Diketones

A concerted metallophotoredox catalysis has been realized for the efficient decarboxylative functionalization of α,β-unsaturated carboxylic acids with aryl iodides in the presence of perylene bisimide dye to afford 1,2-diketones.

Catalyst-Free and Transition-Metal-Free Approach to 1,2-Diketones via Aerobic Alkyne Oxidation

A catalyst-free and transition-metal-free method for the synthesis of 1,2-diketones from aerobic alkyne oxidation was reported. The oxidation of various internal alkynes, especially more challenging aryl-alkyl acetylenes, proceeded smoothly with inexpensive, easily handled, and commercially available potassium persulfate and an ambient air balloon, achieving the corresponding 1,2-diketones with up to 85% yields. Meanwhile, mechanistic studies indicated a radical process, and the two oxygen atoms in the 1,2-diketons were most likely from persulfate salts and molecular oxygen, respectively, rather than water.

ortho-Ethynyl group assisted regioselective and diastereoselective [2 + 2] cross-photocycloaddition of alkenes under photocatalyst-, additive-, and solvent-free conditions

A highly regioselective and diastereoselective [2 + 2]-cross-photocycloaddition between electron-poor and electron-rich/electron-neutral alkenes under visible-light irradiation without a photocatalyst, additive and solvent was developed.

Recent advances in the transition metal catalyzed synthesis of quinoxalines: a review

This review summarizes the recent developments in the synthesis of a variety of substituted quinoxalines using transition metal catalysts.

Synthesis of unsymmetrical benzils via palladium-catalysed α-arylation-oxidation of 2-hydroxyacetophenones with aryl bromides

A diverse set of unsymmetrically substituted benzils were facilely synthesised by a cross-coupling reaction between 2-hydroxyacetophenones and aryl bromides in the presence of a palladium catalyst. Experimental studies suggested a reaction mechanism involving a one-pot tandem palladium-catalysed α-arylation and oxidation, where aryl bromides play a dual role as mild oxidants as well as arylating agents.

Cobalt(II)-Catalyzed [4+2] Annulation of Picolinamides with Alkynes via C-H Bond Activation

A cobalt(II)-catalyzed [4+2] annulation of picolinamides with alkynes via C-H bond activation has been developed. The operationally simple annulation reaction allows for the synthesis of acyl-substituted 1H-benzoquinoline bearing multiple aromatic rings (up to 96 % yield) without co-oxidant or other oxidation factors under mild conditions. Several control experiments were carried out. This practical [4+2] annulation provides an efficient route to access highly functionalized compounds.

One-pot preparation of hyaluronic acid-coated iron oxide nanoparticles for magnetic hyperthermia therapy and targeting CD44-overexpressing cancer cells

In the present study, a facile one-pot hydrothermal method is introduced for preparation of hyaluronic acid-coated Fe₃O₄ nanoparticles (Fe₃O₄@HA NPs) for theranostic applications. In the proposed method, hyaluronic acid acts simultaneously as a biocompatible coating layer and as a targeting ligand for CD44 receptor overexpressed on the surface of breast cancer cells. The obtained product with narrow hydrodynamic size distribution exhibited a high colloidal stability at physiological pH for more than three months. Cytotoxicity measurements indicated a negligible toxicity of the prepared sample against L929 normal cells. Preferential targeting of Fe₃O₄@HA NPs to CD44-overexpressing cancer cells was studied by comparing the uptake of the prepared nanoparticles by MDA-MB-231 cancer cells (positive CD44 expression) and L929 normal cells (negative CD44 expression). Uptake of the Fe₃O₄@HA NPs by MDA-MB-231 cells was found to be 4-fold higher than the normal cells. Also, the in vitro analysis showed that, the uptake of Fe₃O₄@HA NPs by MDA-MB-231 breast cancer cells is significantly enhanced as compared to non-targeted dextran-coated Fe₃O₄ NPs. Moreover, the heat generation capability of the Fe₃O₄@HA NPs for magnetic hyperthermia application was studied by exposing the prepared nanoparticles to different safe alternating magnetic fields (f = 120 kHz, H = 8, 10, and 12 kA/m). The intrinsic loss power obtained for Fe₃O₄@HA NPs was about 3.5 nHm²/kg, which is about 25-fold larger than that of obtained for commercial available Fe₃O₄ nanoparticles for biomedical applications. Good colloidal stability, biocompatibility, high heating efficacy, and targeting specificity to CD44 receptor-overexpressing cancer cells could make the Fe₃O₄@HA NPs as a promising multifunctional platform for diagnosis and therapeutic applications.