Tandem oxidative amidation of benzylic alcohols by copper(II) supported on metformin-graphitic carbon nitride nanosheets as an efficient catalyst

In this research, an efficient heterogeneous catalyst based on graphitic carbon nitride nanosheets (CN) has been reported. The CN was functionalized by 1,3-dibromopropane as a linker (CN–Pr–Br) and subsequently modified with metformin (CN–Pr–Met). Furthermore, the copper(II) was coordinated on modified CN (CN–Pr–Met–Cu(II)) and during this process, 7.94% copper(II) was loaded into the catalyst structure. The synthesized catalyst was evaluated by various techniques including fourier-transform infrared spectroscopy (FT-IR), energy dispersive X-ray spectroscopy (EDS), field emission scanning electron microscopy (FE-SEM), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and inductively coupled plasma atomic emission spectroscopy (ICP-OES). CN–Pr–Met–Cu(II) was used as a catalyst in the synthesis of amides via the oxidation of benzyl alcohols. The conditions of this reaction were optimized in terms of temperature, time, amount of catalyst, type of base, oxidant, and solvent. Moreover, a variety of amides with an efficiency of 75–95% were synthesized. The reaction was carried out in the presence of benzyl alcohols, amine hydrochloride salts, tert-butyl hydroperoxide (TBHP), CaCO(3), and CN–Pr–Met–Cu(II) at 80 °C of acetonitrile solvent. The synthesized catalyst can be easily separated from the reaction medium and reused for 7 consecutive runs without a significant reduction in reaction efficiency.