Highly efficient and catalyst-free ring-closing reaction of 2′-hydroxychalcones into potential bioactive flavanones

Ionic liquids are known as useful and eco-friendly solvents due to their low vaporisation and suitable physicochemical properties. The synthesis of flavanones <i>via</i> the reversible ring-closing reaction of 2′-hydroxychalcones with or without catalysts in the presence of various ionic liquids has been studied. Under optimal conditions, seventeen flavanones were obtained in yields ranging from 38% to 88% in 1–8 h, depending on the substituents of 2′-hydroxychalcones. Besides, the high recyclability of [Bpy]Br, which could be recycled four times without any significant decrease in yield, is an important highlight of the present method. Furthermore, seven of the synthesised flavanones were selected for testing their <i>in vitro</i> anticancer efficacy against lung (A549) and breast (MCF-7) cancer cells. The screening led to the identification of a potent inhibitor, 4′-hydroxy-3′-methoxyflavone, <b>2 m</b>, for further testing against liver (HepG2) and cervix (HeLa) cancer cells.