One-Pot Green Synthesis of 2-Oxo-2H-chromene-3-carbonitriles Using Dual-Frequency Ultrasonication

A green synthesis of 2-oxo-2H-chromene-3-carbonitriles has been carried out in one step by reacting 2-hydroxybenzaldehydes or 2-hydroxyacetophenones with ethyl cyanoacetate under dual-frequency ultrasonica­tion (ultrasonic bath of 40 KHz and probe of 20 KHz). The compounds were obtained in very high yield, and their structures were confirmed by IR and NMR data.