Selective synthesis of (1H-benzo[d]imidazol-2-yl)(phenyl)methanone and quinoxaline from aromatic aldehyde and o-phenylenediamine.

We have designed a general, inexpensive, and versatile method for the synthesis of (1H-benzo[d]imidazol-2-yl)(phenyl)methanone and the formation of C-N bonds via an aromatic aldehyde and o-phenylenediamine. In the presence of N,N-dimethylformamide/sulfur, (1H-benzo[d]imidazol-2-yl)(phenyl)methanone was obtained; however, in the absence of sulfur, quinoxaline was obtained in 1,4-dioxane. A wide range of quinoxalines and (1H-benzo[d]imidazol-2-yl)(phenyl)methanones was obtained under mild conditions.