Ultrasound-assisted Synthesis of Azlactone and its Reactions with Nucleophiles

4-(2-Oxoindolin-3-ylidene)-2-phenyl-5(4 H )-oxazolone (azlactone) was synthesized as a mixture of E - and Z -isomers by ultrasound-assisted Erlenmeyer–Plochl reaction between isatin and N -benzoylglycine. Treatment of azlactone with nucleophiles causes opening of its oxazolone moiety.