Abstract
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), CaCO3, 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.
Highlights
Carbon-based nanomaterials including carbon nanotubes, graphene, and graphitic carbon nitride (g-C3N4) have become important topics in a variety of scientific fields in recent y ears[1,2]
Carbon and hydrogen nuclear magnetic resonance (NMR) spectroscopy were used to evaluate the structure of some products and for this purpose VARIAN Inova 500 MHz and 125 MHz devices were used
Bulk g-C3N4 was prepared according to an article published by Zheng et al.41. 10 g of melamine powder was heated in a furnace at 550 °C for 4 h under air atmosphere
Summary
Carbon-based nanomaterials including carbon nanotubes, graphene, and graphitic carbon nitride (g-C3N4) have become important topics in a variety of scientific fields in recent y ears[1,2]. Synthesis of amide by the mentioned methods has disadvantages such as high cost, producing a lot of wastes, low efficiency, and the use of toxic reagents. Alternative methods such as oxidative amidation of aldehydes or alcohols have been r ecommended[34]. Tandem oxidative amidation of benzylic alcohols was catalyzed by a series of transition metals[35–38] Among these metals, copper(II) with low price and high biocompatibility has been considered efficient catalysts for the amidation of alcohols[39,40]. The prepared catalyst contains 7.94% copper(II) and the synthesis of amides was greatly facilitated by this method This catalyst was used 7 times in the tandem oxidative amidation of benzylic alcohols without significantly reducing the efficiency of the products. The obtained yellow powder was ground for further usage
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