Solvent-free, microwave assisted Knoevenagel condensation of novel 2,5-disubstituted indole analogues and their biological evaluation

A rapid, efficient and environmental benign methodology for the preparation of 2,5-disubstituted indole analogues is developed. 2,5-Disubstituted indole-3-carboxaldehydes (1a–c) undergo Knoevenagel condensation with barbiturates (2 & 4), thiazolidine-2,4-dione (6) and 3-methyl-1H-pyrazol-5(4H)-one (8) in solvent-free, NH4OAc catalyzed, microwave assisted reaction. Structures of the products thus obtained were confirmed by their m.p, Elemental analysis, IR, 1H NMR, 13C NMR and Mass spectral data. The in vitro antioxidant and cytotoxic activities against three tumor cell lines were evaluated and discussed in terms of their structural differences. Among the screened compounds 9b, 9c, 7b and 5b exhibited excellent antioxidant activity. Compounds 9b, 9c and 7b have shown strong cytotoxicity among the compounds tested.

Graphical abstractA new series of novel indole analogues were synthesized and evaluated for their antioxidant and cytotoxic activities.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The method is rapid, expedient and environmental benign. ► Microwave assisted synthesis has produced excellent yields with high purity. ► Compound 9b and 9c have shown excellent antioxidant potentialities. ► Compound 9b and 9c have shown effective cytotoxicity.