Ni-nanoparticles: An efficient catalyst for the synthesis of quinoxalines

Biologically active quinoxalines were efficiently synthesized in excellent yields and in less reaction time using inexpensive, monodispersed and easily recyclable Ni-nanoparticles. In order to elucidate the role of the Ni-nanoparticles, a control reaction was conducted using glyoxal and o-phenylenediamine in acetonitrile in the absence of Ni-nanoparticles. Quinoxaline was formed in around 10 h with a 30% yield. However, the same reaction carried out in acetonitrile using 10 mol% of Ni- nanoparticles (14–18 nm) at 25 °C and stirred under N2 gave quinoxaline in quantitative yield in 10 min. The separation of the product was facile and the catalyst could be separated and recycled by mild centrifugation. Our method is very quick, avoids the use of expensive reagents, high temperatures (our reaction takes place at room temperature) and leads to excellent yield.