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A rapid and green procedure has been introduced for the preparation of pyrano[2,3-c]pyrazole and xanthene-1,8-dione derivatives in the presence of a natural catalyst in aqueous medium. Sodium tetraborate pentahydrate was found as a nontoxic or minimally toxic, readily available, cheap, and ecologically favorable agent catalyst for the synthesis of these important heterocyclic compounds. The introduced method offers some advantages such as high efficiency, an inexpensive and easy-to-handle catalyst, avoidance of organic solvents, and simple work-up that they are consistent with green chemistry. [ABSTRACT FROM AUTHOR]

Abstract In this study, a new and efficient magnetic composite was synthesized based on graphene oxide (GO). Initially, GO was coated with magnetite, and then Ti(IV ) was fixed on GO-Fe3O4 via a covalent graft. The magnetic composite was characterized by FT-IR, EDS, XRD, FE-SEM, TEM, VSM and TGA techniques. It was designed as a compound with strong and recoverable catalytic properties. The prepared GO-Fe3O4-Ti(IV) emerged to be of high catalytic activity for the synthesis of bis(indolyl)methane and benzo[a]xanthen-11-one derivatives under mild conditions. The stability and reusability of the catalyst were investigated too. All of the data proved that GO-Fe3O4-Ti(IV) could be recycled five times without a marked loss of activity. [ABSTRACT FROM AUTHOR]