Efficient Catalytic Synthesis of Xanthenes with Copper Immobilized on Amine-Modified NaY

The purpose of this article is to describe the synthesis of copper-amine complexes on nano NaY zeolite (Cu@NNPS-NaY), as a highly efficient, reusable, and environmentally friendly catalyst for the xanthenes synthesis. The Cu@NNPS-NaY catalyst was prepared from the reaction of silane-bonded nano NaY Zeolite (CPS-NaY) with [2-({3-[(2-aminoethyl) thio]propyl} thio)ethyl]amine (NN) followed by immobilizing copper ions onto the NNPS-NaY surface. The catalyst structure was characterized using FT-IR, XRD, TGA, EDS, DLS, SEM, TEM, ICP, and elemental analyses. The bonded long-chain amine including heteroatoms on the zeolite surface improved its catalytic activity and homogeneity, making it more capable of coordinating with copper ions. Synthesis of xanthenes was performed in the presence of Cu@NNPS-NaY catalyst (30 mg) in EtOH (10 mL) at 60 °C within 10-60 minutes resulting in product yields of 84-97%. The prepared catalyst can be easily recovered by centrifugation and reused for at least twelve consecutive runs with no significant loss of its catalytic activity. Besides the simplicity of catalyst recovery and reusing, the method is easy to set up and versatile, making it an environmentally friendly way to prepare titled heterocycles. Based on the results of this study, other useful heterocycles could be synthesized under eco-friendly conditions using this catalytic system.