Co3O4/NiO@GQDs@SO3H nanocomposite as an effective catalyst for the synthesis of pyranopyridines

Co3O4/NiO@GQDs@SO3H nanocatalyst has been used as an effective catalyst for the preparation of benzopyranopyridines through a four-component reaction of salicylaldehydes, thiols and 2 equiv of malononitrile under reflux condition in ethanol. The catalyst has been characterized by FT-IR, XRD, SEM, EDS, BET, XPS, TGA and VSM. Atom economy, reusable catalyst, low catalyst loading, applicability to a wide range of substrates and high yields of products are some of the notable features of this method. The best results were gained in EtOH and we found that the reaction gave convincing results in the presence of Co3O4/NiO@GQDs@SO3H nanocomposite (4 mg) under reflux conditions. A series of salicylaldehydes and different thiols were studied under optimum conditions.We also determined recycling of Co3O4/NiO@GQDs@SO3H nanocomposite as catalyst for the model reaction under reflux conditions in ethanol. The results showed that nanocomposite can be reused several times without noticeable loss of catalytic activity (Yields 90 to 88%)