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, NH(4)OAc catalyzed, microwave assisted reaction. Structures of the products thus obtained were confirmed by their m.p, Elemental analysis, IR, (1)H NMR, (13)C 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.