Graphite catalyzed green synthesis of quinoxalines

A new simple approach using environmentally benign, cheap, and easily recyclable graphite as a heterogeneous catalyst for the synthesis of quinoxalines is described. A library of pharmacologically interesting diphenylquinoxalines is prepared by the double condensation of substituted benzils, phenanthrene-9,10-dione, and benzoin with aromatic diamines in 71–93% yields at room temperature in ethanol. Aliphatic diamines gave corresponding dihydropyrazines from substituted benzils in 72–92% yields.