Nitrogen‐Doped Graphene Oxide as a Sustainable Carbonaceous Catalyst for Greener Synthesis: Benign and Solvent‐free Synthesis of Pyranopyrazoles

Abstract

The development of benign strategies using the greener catalytic system is one of the prime tasks to improvise the greenness and sustainability in the synthesis of bioactive molecules. In the present work, a straightforward and sustainable methodology for the one-pot synthesis of dihydropyrano [2,3-c] pyrazole has been developed using nitrogen-doped graphene oxide (NGO) as a solid carbocatalyst under neat condition. The presence of high-density different types of nitrogen on the basal plane and the edges of the graphitic surface renders excellent active alkali sites and make it as a carbonaceous catalyst for the synthesis of a wide range of pyranopyrazoles with excellent yield. Present carbonaceous NGO catalysis the formation of pyranopyrazoles from diverse aldehydes and ketones under a solvent-free simple grinding condition that avoids chromatographic purifications. In this benign multicomponent synthesis, the NGO is highly stable and reusable without any loss in its catalytic activity even after eight successive reuses, which strongly enlighten the sustainable nature of the catalyst. Further analytical studies of the reused catalyst confirm the stability of the catalyst even after several reuses. The NGO catalyst paves a path for the development of sustainable nitrogen-based carbocatalyst for the benign multicomponent synthesis of bioactive molecules.

Green multicomponent synthesis of pyrano[2,3-c]pyrazole derivatives: current insights and future directions

“…S. Ganesan and P. Suresh 110 hydrothermally synthesized nitrogen-doped graphene oxide (NGO) and investigated its application as a solid-base heterogeneous catalyst for pyranopyrazoles synthesis. Malononitrile, ethyl acetoacetate, hydrazine hydrate, and different functional groups of substituted aldehydes were combined in a condensation reaction under solvent-free conditions using a grinding technique, yielding high yields of pyranopyrazoles within 2 min ( Scheme 64 ).…”

Graphene‐Based Nanomaterials for Biomedical, Catalytic, and Energy Applications

“…[60] A recent investigation by Ganesan et al reported the fabrication of nitrogen-doped graphene oxide (NGO) through a hydrothermal route and its use as a solid catalyst for facile and one-pot synthesis of dihydropyrano[2,3-c]pyrazole with good atom economy. [61] The nitrogen-rich graphene-based solid catalyst could be reused multiple times (∼ eight times) without any significant decrease in its catalytic activity, thereby providing a stable, solvent-free, sustainable, neat, and greener synthetic approach.…”

Microwave‐assisted exfoliation of graphite using 1‐allyl‐pyridinium‐based ionic liquids and application to solid acid catalysts

“…Due to the large theoretical surface area of graphene (2630 m 2 /g), 22 several recent studies have been reported for the fabrication of more unique materials, such as graphene and graphene oxide (GO), as solid acid catalysts and their application in phenol degradation, 23 isoxazole and pyranopyrazole synthesis, 24 selective reduction of substituted nitro groups, 25 dihydropyrano [2,3‐c] pyrazole synthesis, 26 esterification of acetic acid with n ‐butanol, 27 and 2,4‐disubstituted quinoline synthesis 28 . Focusing on the saccharification of cellulose, a GO catalyst prepared through the modified Hummers' method and sonication was used in the saccharification of cellulose at 150°C for 24 h, resulting in a glucose yield of 21.4% 29 .…”