Rapid and Efficient One-Pot Synthesis of 3,4-Dihydroquinoxalin-2-Amine Derivatives Catalyzed by Co3O4@SiO2 Core-Shell Nanoparticles Under Ultrasound Irradiation.

In this research, a general synthetic method for the synthesis of 3,4- dihydroquinoxalin-2-amine derivatives was developed using Co3O4@SiO2 nanoparticles under ultrasonic irradiation. Firstly by a simple and green process, Co3O4;@SiO2 nanoparticles were prepared via sonication, and then these nanoparticles were used as an efficient catalyst for the synthesis of 3,4- dihydroquinoxalin-2-amines via three-component reactions of ophenylenediamines (OPDA), diverse ketones and various isocyanides in ethanol under ultrasound irradiation. The combinatorial synthesis was attained for this procedure with applying ultrasound irradiation while making use of ethanol as green ambient. The present approach offers several advantages such as high yields, environmentally benign, simple work-up, excellent yield of products and short reaction times. The nanomagnetic catalyst could be readily recovered using a simple external magnet and reused several times without any significant loss in activity. The catalyst was fully characterized by FT-IR, FE-SEM, XRD, EDX, VSM and TEM analysis.