Reduced Graphene Oxide Supported Copper Oxide Nanocomposites from a Renewable Copper Mineral Precursor: A Green Approach for Decarboxylative C(sp³)–H Activation of Proline Amino Acid To Afford Value-Added Synthons

Abstract

A green approach for decarboxylative C­(sp3)–H activation of proline amino acid was accomplished by coupling with aldehydes and alkynes to afford α-alkynylated N-substituted pyrrolidines as value-added synthons using reduced graphene oxide supported copper oxide (RGO@CuO) nanocatalysts. The RGO@CuO nanocomposites were obtained by the impregnation of micrometer-sized malachite spheres, as a renewable and sustainable copper mineral precursor, on the graphene oxide (GO) sheets followed by calcination at 300–450 °C for 5 h. The characterization of as-synthesized composites revealed the generation of monodispersed and uniformly embedded copper oxide (CuO) nanoparticles with sizes ranging from 10 to 15 nm on RGO thin sheets via GO as a support as well as indirect template for dissembling and decomposition of micrometer-sized malachite spheres. The RGO@CuO composites were found to be efficient and robust nanocatalysts compared with CuO nanoparticles (NPs) alone. The present method offers several advantages, such as wide substrate scope, and avoids the usage of excess equivalent of substrates with minimal waste generation (E-factor = 0.24) and high reaction mass efficiency (80.7%), and the nanocatalyst was recycled for five times without significant loss in its activity with a negligible leaching of CuO NPs from RGO sheets.

Synergistic Catalysis by Copper Oxide/Graphene Oxide Nanocomposites: A Facile Approach to Prepare Quinazolines and Quinazoline Containing Triazole/Tetrazole Moieties under Mild Reaction Conditions

“…The Cu 2p XPS spectrum (Figure 5d) of CuO/GO nanocomposite shows two bands at 934.6 and 954.5 eV, which are associated to the bonding energy of Cu 2p 3/2 and Cu 2p 1/2 , respectively. Additionally, two satellite peaks observed at 943.8 and 963.3 eV corresponds to Cu 2p 3/2 and Cu 2p 1/2 , suggesting the presence of Cu +2 in the prepared catalyst and hence the formation of CuO is confirmed [51,53] …”

“…This suggests the presence of more defects in CuO/GO nanocomposite. [50][51][52] The chemical composition and the oxidation state of copper in CuO/GO nanocomposite were investigated by XPS analysis as shown in Figure 5. The XPS survey spectrum (Figure 5a) shows the presence of Cu, C and O elements in the prepared CuO/GO nanocomposite.…”

Solvent‐free synthesis of propargylamines via A3 coupling reaction and organic pollutant degradation in aqueous condition using Cu/C catalyst

“…Copper exists in Cu 2+ oxidation state, which was confirmed by the presence of Cu 2p 1/2 and Cu 2p 3/2 peaks with binding corresponding energies of 952.6 eV and 932.6 along with their satellite peaks at 940.8 and 960.6 eV, respectively, as shown in the high‐resolution spectra of the Cu2p region. [ 37–39 ] The XPS spectra also showed binding energy of 930.6 eV, which corresponds to copper present in the metallic state on the catalyst surface as shown in Figure 3b–f. [ 40 ] The loading of Cu in the synthesized Cu/C catalyst was found to be 2.86 wt.%, as determined by ICP‐MS.…”

An efficient Cu/functionalized graphene oxide catalyst for synthesis of 5-substituted 1H-tetrazoles

“…Two peaks 1733.02 cm −1 corresponding to the amide carbonyl (C=O) stretch and the peak at about 1539.03 cm −1 (C-N) which may be due to copper oxide nanocomposite (Rani et al 2014). The peak at 535.57 cm −1 corresponds to Cu-O stretching vibration characteristic of CuO nanoparticles (Gulati et al 2018).…”