An efficient and base-free approach has been described for the synthesis of an array of quinoxalines by the annulation reaction of terminal alkynes with o-phenylenediamines in the presence of cobalt-doped-magnesium oxide (Co-MgO) as a heterogeneous nanocatalyst. This method has been successfully employed for the synthesis of a wide range of functionalized quinoxalines in high yields (70-90 %). All products were isolated either as solid or liquid and fully authenticated by 1H and 13C NMR spectral data. Operationally, the reaction protocol is simple, mild, and base-free. The Co-MgO catalyst can be successively reused for four runs with a negligible loss in catalytic activity. Five green chemistry metrics, i.e., AE, E-Factor, CE, PMI, RME for the reaction were calculated and found to be in close proximity to the ideal values, suggestive of environmental acceptability of the reaction protocol. The broad functional group tolerance and a mechanistically different approach may be a potent supplement to conventional methods for the synthesis of quinoxalines.

A new biocomposite of chitosan, chitosan-supported di(pyridine-2-yl)methanone-Ni(II) complex, CS-DPM-Ni, is synthesized for the first time. The biocomposite is thoroughly characterized by FTIR, PXRD, XPS, FESEM, EDX, TGA, ICP-OES, and elemental analysis. The synthesized composite is successfully used as a heterogeneous catalyst in the synthesis of a library of xanthone derivatives by the intermolecular catalytical coupling of 2 substituted benzaldehydes and phenols. The catalyst could be retrieved from the reaction mixture by simple filtration and reused for up to four catalytic cycles. All products were isolated in good to high yields (65-90 %) with good turnover numbers (TONs), and fully characterized by 1H and 13C{1H} NMR spectroscopy. The green chemistry metrics values for the reaction were discerned and found to be close to the ideal values.

A copper-triazine-dendrimer-functionalized graphene oxide (CTD-GO) is synthesized for the first time. The structure of the dendrimer is confirmed by Fourier transform infrared (FT-IR), Fourier transform (FT) Raman, powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), elemental mapping, atomic absorption spectroscopy (AAS), and thermogravimetric analysis (TGA). The catalytic activity of the CTD-GO is demonstrated in green synthesis of a series of propargylamine derivatives in high yields via A(3)-coupling of aldehyde, alkyne, and amine in water. After the reaction, the catalyst was easily recuperated from the reaction mixture and reused up to four times without any significant loss in its catalytic activity. Operational simplicity, high yields of product, use of green solvent, facile recovery and recyclability of the catalyst, and easy workup are the salient features of this procedure.