Base Promoted Tandem Cyclization ofo‐Phenylenediamine with Ninhydrin‐phenol Adducts: An Unprecedented Route to Phenol Appended Isoindolo[2,1‐a]quinoxaline Fluorophore

Synthesis, Physicochemical Characterization, Biological Assessment, and Molecular Docking Study of Some Metal Complexes of Alloxan and Ninhydrin as Alterdentate Ligands

A series of transition metal complexes of alloxan monohydrate (H2L1) and ninhydrin (H2L2) have been prepared where metal ions are Fe(III), Co(II), Ni(II), Cu(II), Zr(IV), and Mo(VI). Different microanalytical techniques, spectroscopic methods, and magnetic studies were applied to assign the mode of bonding and elucidate the structure of complexes. All solid complexes are of 1:1 (M:L) stoichiometry and octahedral geometry except nickel (II) complexes exist in a tetrahedral geometry. FTIR spectral interpretation reveals that HL1 coordinates to the central metal ion in a bidentate ON pattern, whereas HL2 behaves as an alterdentate ligand through hydroxyl oxygen and carbonyl oxygen either C(1) = O or C(3) = O. The thermal behavior of some complexes was followed up to 700 °C by different techniques (TGA, DTA, and DSC) where decomposition stages progress in complicated mechanisms and are ended by the formation of metal oxide residue. Besides, biological screening involving antioxidant, antibacterial, and antifungal for ligands and some of their complexes was done. Moreover, four examined metal complexes displayed anticancer activity against hepatocellular carcinoma cells (HepG-2) but to different degrees. According to the IC50 values, Cu-ninhydrin complex, [Cu(HL2)(H2O)4].Cl has a better potency impact in comparison with cisplatin which was used as a reference control. This is in harmony with the molecular docking simulation outcomes that predicted a good binding propensity of the Cu-ninhydrin complex with hepatocellular carcinoma protein (2jrs). Therefore, the Cu-ninhydrin complex should be deemed as a potential chemotherapeutic agent for hepatocellular cancer.

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Supplementary Information

The online version contains supplementary material available at 10.1007/s10904-023-02661-5.

Recent advances in the transition-metal-free synthesis of quinoxalines

Quinoxalines, also known as benzo[a]pyrazines, constitute an important class of nitrogen-containing heterocyclic compounds as a result of their widespread prevalence in natural products, biologically active synthetic drug candidates, and optoelectronic materials. Owing to their importance and chemists' ever-increasing imagination of new transformations of these products, tremendous efforts have been dedicated to finding more efficient approaches toward the synthesis of quinoxaline rings. The last decades have witnessed a marvellous outburst in modifying organic synthetic methods to create them sustainable for the betterment of our environment. The exploitation of transition-metal-free catalysis in organic synthesis leads to a new frontier to access biologically active heterocycles and provides an alternative method from the perspective of green and sustainable chemistry. Despite notable developments achieved in transition-metal catalyzed synthesis, the high cost involved in the preparation of the catalyst, toxicity, and difficulty in removing it from the final products constitute disadvantageous effects on the atom economy and eco-friendly nature of the transformation. In this review article, we have summarized the recent progress achieved in the synthesis of quinoxalines under transition-metal-free conditions and cover the reports from 2015 to date. This aspect is presented alongside the mechanistic rationalization and limitations of the reaction methodologies. The scopes of future developments are also highlighted.

Recent applications of ninhydrin in multicomponent reactions

Ninhydrin (1,2,3-indanetrione hydrate) has a remarkable breadth in different fields, including organic chemistry, biochemistry, analytical chemistry and the forensic sciences. For the past several years, it has been considered an important building block in organic synthesis. Therefore, there is increasing interest in ninhydrin-based multicomponent reactions to rapidly build versatile scaffolds. Most of the works described here are simple reactions with readily available starting materials that result in complex molecular architectures. Some of the synthesized compounds exhibit interesting biological activities and constitute a new hope for anticancer agents. The present review aims to highlight the multicomponent reactions of ninhydrin towards diverse organic molecules during the period from 2014 to 2019.

This article aims to review recent multicomponent reactions of ninhydrin towards diverse organic scaffolds, such as indeno-fused heterocycles, spiro-indeno heterocycles, quinoxalines, propellanes, cage-like compounds, and dispiro heterocycles.

Annulations involving 2-arylidene-1,3-indanediones: stereoselective synthesis of spiro- and fused scaffolds

Stereoselective annulations of 2-arylidene-1,3-indanediones towards spiro-carbocycles as well as spiro/fused heterocycles based on various cycloadditions and tandem annulations are described.