A straightforward, simple and unprecedented transformative protocol has been accomplished towards furnishing a wide variety of pharmaceutically promising functionalised 3‐methyl‐4‐(hetero)arylmethylene isoxazole‐5(4H)‐ones and 6‐Amino‐3‐methyl‐4‐phenyl‐1,4‐[2,3‐c]pyrazole‐5‐carbonitriles. Sulfonated graphene oxide (SGO), a new class of heterogeneous carbocatalyst, was found to be efficient for thisone pot rapid conversion of isoxazoles and pyranopyrazoles from aldehyde. The prepared SGO was characterised by FEG‐SEM, HR‐TEM, FTIR and was recyclable up to 5th run without a significant drop in its catalytic activity. Metal free synthesis, good to excellent yield, high atom economy, usage of readily available starting material, operational simplicity, easy workup, and recyclable catalyst are the fundamental features of this protocol.
A simple and highly efficient method for the synthesis of 5‐aryl‐pyrimido quinoline 2,4‐diones has been demonstrated. Graphene oxide (GO) has proved to be a new class of carbocatalyst for the synthesis of pyrimido[4,5‐b]quinolinone‐2,4‐diones through one‐pot three component reaction using aromatic amines, aldehydes, and barbituric acid. The antimicrobial activity of the synthesized compounds was examined for the first time. The effects e. g. reaction temperature, catalyst amount, reaction time, the molar ratio of reactants were investigated. The GO could easily be recovered and reused upto 5th run without loss of its catalytic activity.
An efficient, straight forward, eco‐friendly procedure for the synthesis of biologically active hexahydroquinoline derivatives and hexahydroacridine‐1,8‐diones has been designed using a novel bio‐degradable heterogeneous catalyst, sulphonated rice‐husk (SRH). SRH provides high density of acid groups making it different from conventional solid acids containing single acid groups. We report an efficient protocol for the synthesis of hexahydroquinolines and hexahydroacridine‐1,8‐diones using this carbon based acid catalyst (SRH) in solvent free and greener solvent respectively. Moreover, operational simplicity, greener reaction condition, reusability of the catalyst, excellent yield (upto 98 %) are the fundamental features of this protocol. The metal free catalyst was characterised using different spectroscopic techniques FTIR, SEM, EDX, Powder XRD, ICP‐AES.
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