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Abstract: Recyclable Ni-nanoparticles provides an efficient, economic and rapid method for catalyzing Knoevenagel condensation of aldehydes with an active methylene compound at room temperature. The method offers high yield preferably in case of aromatic aldehydes and proceed well in neutral medium. This method provides a wide range of substrate applicability and simple workup procedure. The products need no further purification and the process is environmentally benign. [Copyright &y& Elsevier]

Abstract: 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 10h with a 30% yield. However, the same reaction carried out in acetonitrile using 10mol% of Ni- nanoparticles (14–18nm) at 25°C and stirred under N2 gave quinoxaline in quantitative yield in 10min. 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. [Copyright &y& Elsevier]