Heterocyclic moiety serve as perfect framework on which pharmacophores can be effectively attached to produce novel drugs. Among various heterocyclic compounds, nitrogen-based heterocycles have been extensively investigated as they constitute the core structures of numerous biologically relevant molecules and have been found to be active against different types of cancers. Due to the versatility of indole, it has been a highly "privileged motif" for the target-based design and development of anticancer agents. Moreover, it has been used as a synthon for the preparation of large number of bioactive heterocycles and paved a way to develop effective targets. This review article presents comprehensive overview of anticancer potentiality of diversely substituted indole derivatives including 1H-indole-2,3dione and Spiro indole derivatives.

Graphene is considered a promising catalyst candidate due to its 2D nature, single-atom thickness, zero bandgap and very high surface to volume ratio. Further, graphene oxide (GO) has been used as a catalytic support material for metal/metal oxide nanoparticles due to its tunable electrical properties. In addition, its high chemical stability and ultrahigh thermal conductivity may possibly promote high loading of catalytically active sites. This review article focuses on the recent progress in the catalytic applications of GO especially (i) as catalytic-support material (GO/reduced graphene oxide supported metal/metal oxide nanohybrids) for the green synthesis of biologically relevant molecules, (ii) for metal-free catalysis and (iii) for electrocatalysis, with special focus on graphene contribution to catalytic efficiency. The critical overview and future perspectives are also discussed.

Various Biginelli compounds (dihydropyrimidinones) have been synthesized efficiently and in high yields under mild, solvent-free, and eco-friendly conditions in a one-pot reaction of 1,3-dicarbonyl compounds, aldehydes, and urea/thiourea/acetyl thiourea using lithium-acetate as a novel catalyst without the addition of any proton source. Comparative catalytic efficiency of lithium-acetate and polyphosphoric acid to catalyze Biginelli condensation is also studied under neat conditions. The reaction is carried out in the absence of any solvent and represents an improvement of the classical Biginelli protocol and an advantage in comparison with FeCl3 ·6H2O, NiCl2 ·6H2O and CoCl2 ·6H2O that were used with HCl as a cocatalyst. Compared to classical Biginelli reaction conditions, the present method has advantages of good yields, short reaction times, and experimental simplicity. The obtained products have been identified by spectral (1H NMR and IR) data and their melting points. The prepared compounds are evaluated for anticancer activity against two human cancer cell lines (lung cancer cell line A549 and breast cancer cell line MCF7).

An extremely efficient catalytic protocol for the synthesis of a series of pyranopyrazole derivatives developed in a one-pot four-component approach in the presence of ZnO nanoparticles as heterogeneous catalyst using water as a green solvent is reported. Greenness of the process is well instituted as water is exploited both as reaction media and medium for synthesis of catalyst. The ZnO nanoparticles exhibited excellent catalytic activity, and the proposed methodology is capable of providing the desired products in good yield (85–90%) and short reaction time. After reaction course, ZnO nanoparticles can be recycled and reused without any apparent loss of activity which makes this process cost effective and hence ecofriendly. All the synthesized compounds have been characterized on the basis of elemental analysis, IR, 1H NMR, and 13C NMR spectral studies.

A simple catalytic protocol for the synthesis of novel spiro[indoline-pyranodioxine] derivatives has been developed using ZnO nanoparticle as an efficient, green, and reusable catalyst. The derivatives are obtained in moderate to excellent yield by one-pot three-component reaction of an isatin, malononitrile/ethylcyanoacetate, and 2,2-dimethyl-1,3-dioxane-4,6-dione in absolute ethanol under conventional heating and microwave irradiation. The catalyst was recovered by filtration from the reaction mixture and reused during five consecutive runs without any apparent loss of activity for the same reaction. The mild reaction conditions and recyclability of the catalyst make it environmentally benign synthetic procedure.

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An efficient catalytic protocol for the synthesis of novel spiro[indoline-3,4′-pyrano[2,3-c]thiazole]carbonitriles and condensed thiazolo[5′′,4′′:5′,6′]pyrano[4′,3′:3,4]furo[2,3-b]indole derivatives is developed in a one-pot three-component approach involving substituted 1H-indole-2,3-diones, activated methylene reagent, and 2-thioxo-4-thiazolidinone under conventional heating and microwave irradiation. This paper describes the use of NiO nanoparticles as catalyst for the synthesis of novel spiro and condensed indole derivatives by Knoevenagel condensation followed by Michael addition. The advantageous features of this methodology are operational simplicity, high yield processing, and easy handling. The particle size of NiO nanoparticle was determined by XRD. After reaction course, NiO nanoparticles can be recycled and reused without any apparent loss of activity.

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