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Background  The carbonyl group at position 2 of  N -acetylisatin behaves as an amide which is more susceptible to nucleophilic attack via ring-opening in the presence of nucleophiles. Because of this behavior, in the present work we describe the microwave synthesis of a series of α-ketoamide and  bis -(α-ketoamide) derivatives via the facile ring-opening of  N -acylisatin with different amines and diamines. The microwave irradiation afforded the product in less reaction time, higher yield and purity. Reaction of  N -acylisatin with methanol under microwave irradiation afforded the α-phenylglyoxyl methyl ester derivatives with excellent yields and purities. Aminolysis of the ester derivatives with piperidine and morpholine afforded the same α-ketoamide derivatives obtained from direct aminolysis of  N -acylisatin. The structures of the synthesized compounds were confirmed by FT-IR, NMR, X-ray and elemental analysis.    Results  Reaction of  N -acetylisatin and  N -propoionylsatin with different amines and diamines afforded a series of α-ketoamide and  bis -(α-ketoamide) derivatives respectively via the ring opening of  N -acylisatins. The reaction was performed under conventional condition as well as microwave irradiation. The microwave irradiation afforded the product in less reaction time, higher yield and purity. Reaction of  N -acylisatin with methanol under microwave irradiation afforded the α-phenylglyoxyl methyl ester derivatives in excellent yields and purities as observed from their spectral data. A plausible mechanism involves nucleophilic attack by methanol at C2 carbonyl carbon of  N -acetylisatin and subsequent ring opening to generate the α-ketoester. Aminolysis of α-ketoester with amine afforded the same α-ketoamide which is obtained by direct aminolysis of  N -acylisatin. The IR, NMR spectra, microanalyses, and single crystal X-ray diffraction confirmed the structures of the synthesized compounds.    Conclusions  In conclusion, we have demonstrated that microwave irradiation could be employed efficiently for the synthesis of biologically important α-ketoamide and  bis -(α-ketoamide) derivatives. The microwave irradiation has more advantageous over the classical method with regard to reaction time, solvent quantity, and product yield. Reaction of  N -acylisatin with methanol under microwave irradiation afforded the α-phenylglyoxyl methyl ester derivatives with excellent yields and purities. Aminolysis of the methyl ester derivatives with amine under microwave irradiation afford the same α-ketoamide derivatives as obtained from direct aminolysis of  N -acylisatins.

Microwave irradiation: synthesis and characterization of α-ketoamide and bis (α-ketoamide) derivatives via the ring opening of N-acetylisatin