Silica supported-double metal cyanides (DMCs): A green and highly efficient catalytic protocol for isomerisation of 2′-hydroxychalcones to flavanones

• Ni-, Mn-, Cr-, Zn-HCFe catalysts are used first time in the isomerisation of 2′-hydroxychalcone to flavanone. NiHCFe catalyst is found excellent catalyst during the reaction.
• Reactions are eco-friendly, high yields in shorter time reaction.
• NiHCFe is re-used 6 runs without loss of activity (85% yields).

Four different double metal cyanides (NiHCFe, CrHCFe, MnHCFe and ZnHCFe) were synthesized, followed by adsorbed on silica gel and used as Lewis acid catalyst in the isomerisation of substituted 2′-hydroxychalcones to flavanones under solvent-free (dry) condition. Optimization of the reaction condition, temperature effects, DMC catalysts loading and re-useable catalytic activity were further studied during the reaction. Among these catalysts, NiHCFe at 35 mol% loading gave excellent yield (90%) at 100 °C temperature in 1.15 h. Catalyst (NiHCFe) easily recovered and re-used six times without much loss of its catalytic activity which gave 80–85% product yields each time. However, these DMCs were failed to give product in the solution phase even prolonging the reaction time at reflux temperature. Similarly, isomerization of substituted 2′-aminochalcones gave 2–5% yields either in solution phase or under solvent-free condition.

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