Copper doped K-birnessite as an efficient catalyst for the synthesis of 2-aryl benzimidazoles

In this study, an efficient and highly selective synthesis of 2-aryl benzimidazoles from the reaction of o-phenylenediamine and aromatic aldehydes in the presence of birnessite type copper doped manganese oxide (BCM) is reported. BCM was synthesized by the one-step hydrothermal method. Recycling of BCM up to five runs was investigated with appreciable yield and selectivity of the products. The best overall yields and selectivities were obtained in methanol. The crystal structure and thermal stability of BCM are characterized by using XRD, IR and thermal analysis techniques. The acid sites of BCM were investigated by IR using pyridine as a molecular probe. The improved catalytic activity observed in the BCM catalyst was associated to a high lattice oxygen mobility and availability due to the formation of Cu–O–Mn bridges.