Solvothermal Fabrication of NiO/Co₃O₄ Spherical Composites Modified with N‐Doped Graphene Quantum Dots as a Catalyst in the Microwave‐Assisted Synthesis of Spiro[diindenopyridine‐indoline] Triones

Abstract

N‐Doped Graphene Quantum Dots (N‐GQDs) have been extensively investigated owing to their interesting photochemical, and electrochemical properties. However, N‐GQDs have rarely been introduced as catalyst in organic reactions. Herein, NiO/Co3O4 composites with diverse morphologies of hexagonal nanoplates, spherical, irregular nanocubics, and multishape are fabricated using different solvents and pH adjusters. In the following, the catalytic activity of engineered composites was screened, and it demonstrated to be in the order: spherical>hexagonal nanoplate>irregular solid nanocubic>multi‐shape. The uniform spherical morphology makes exposure of a larger part of the reactive facets possible and provides accessible active sites. Next, novel NiO/Co3O4@N‐GQDs spherical composites has been successfully fabricated by cost‐effective, green and straightforward hydrothermal method. Proposed composite was applied as an efficient heterogeneous catalyst for the microwave‐assisted synthesis of new and known indenospiro derivatives. The desired products were formed in excellent yields (88–97 %) within the short reaction time (6–14 min).

Recent advances in microwave-assisted multicomponent synthesis of spiro heterocycles

“…The reaction was rapid, high yielding, and a non-chromatographic purification protocol was used. 184 …”

“…The reaction was rapid, high yielding, and a non-chromatographic purication protocol was used. 184 In 2021, Maniam et al designed a green and rapid methodology for the synthesis of spirooxindole pyrrolizidines (39) employing a microwave-assisted one-pot, three-component 1,3dipolar cycloaddition of azomethine ylides from L-proline (11) and isatin (1) with various b-nitrostyrenes (38) in methanol as the solvent at 65 °C to obtain products in reasonable-to-high yields (Scheme 13). 185 The structure of (1 0 R,2 0 R,3R)-2 0 -(2,4-dimethoxyphenyl)-1 0nitro-1 0 ,2 0 ,5 0 ,6 0 ,7 0 ,7a 0 -hexahydrospiro[indoline-3,3 0 -pyrrolizin]-2- one (39) was conrmed by single-crystal X-ray analysis.…”