Metal-doped TiO₂nanocatalysts in an MX₂/urea mixture for the synthesis of benzothiazoles bearing substituted pyrrolidin-2-ones: Enhanced catalytic performance and antibacterial activity

Solvents and catalysts are among the key factors in achieving the green chemical synthesis of bioactive compounds. In this regard, metal-doped nanoparticles, as a heterogeneous catalyst, in urea-based deep eutectic mixtures were used to prepare a series of pyrrolidinone-substituted benzothiazoles. In the strategy developed herein, pyrrolidinone derivatives were synthesized by reacting different arylamines with dimethyl itaconate using water as the solvent in a microwave. Then, the as-obtained pyrrolidinone derivatives were reacted with 2-aminothiophenol under microwave irradiation with the assistance of a deep eutectic mixture (CuCl2 or NiCl2/urea) and Cu- or Ni-doped TiO2 nanoparticles to afford the final derivative incorporating both pyrrolidin-2-one and benzothiazole rings. To determine the optimum reaction conditions, the effect of temperature, solvent nature, and reaction time was investigated. Under the optimal operation conditions, high reaction yields were achieved. The developed strategy exhibited advantages of a short reaction time, eco-friendliness, and high productivity. Finally, the obtained derivatives were examined in terms of their antibacterial potential against selected Gram-negative and Gram-positive bacterial strains: Eight of the derivatives exhibited activity against the tested bacteria.