Synthesis and characterization of a novel and green rod‐like magnetic ZnS/CuFe₂O₄/agar organometallic hybrid catalyst for the synthesis of biologically‐active 2‐amino‐tetrahydro‐4H‐chromene‐3‐carbonitrile derivatives

Abstract

The magnetic biocompatible rod-like ZnS/CuFe 2 O 4 /agar organometallic hybrid catalyst was designed and prepared based on a natural macromolecule (agar) through a green and convenient method using inexpensive, nontoxic, and easily available substances. Then, the as-prepared catalyst was characterized by several techniques such as Fourier transform-infrared spectroscopy, energy-dispersive X-ray analysis, scanning electron microscopy image, transmission electron microscopy, vibrating sample magnetometry curve, X-ray diffraction pattern, and thermogravimetric analysis. Eventually, the catalytic application of the ZnS/CuFe 2 O 4 /agar nanobiocomposite was assessed in sequential Knoevenagel condensation-Michael addition reaction of dimedone, malononitrile, and different substituted aromatic aldehydes for the synthesis of 2-amino-tetrahydro-4H-chromene-3-carbonitrile derivatives. Some notable strengths of this environmentally benign catalyst include simplicity of catalyst preparation and separation, affording desired products with satisfactory yields (81%-97%) in very short reaction times (3-18 min), and with no need for complicated work-up processes. Experimental tests showed that the catalyst can be successfully reused after five sequential runs without significant reduction in its catalytic efficiency. K E Y W O R D S 2-amino-tetrahydro-4H-chromene-3-carbonitrile, agar, catalytic synthesis, good reusability, ZnS/CuFe 2 O 4 /agar catalyst

Magnetized melamine‐modified polyacrylonitrile (PAN@melamine/Fe3O4) organometallic nanomaterial: Preparation, characterization, and application as a multifunctional catalyst in the synthesis of bioactive dihydropyrano [2,3‐c]pyrazole and 2‐amino‐3‐cyano 4H‐pyran derivatives

“…The presence of primary, secondary, and tertiary amines (as basic sites) and also Fe 3+ (as a Lewis acidic site) in the structure of prepared nanocomposite plays an important role in the activation of the reactants. Based on previous studies [43], we have proposed a mechanism for the preparation of dihydropyrano[2,3-c]pyrazole derivatives which is depicted in Figure 8. First, the carbonyl groups of ethyl acetoacetate are activated by both the amine groups (by hydrogen bonding) and the Lewis acid sites in the PAN@melamine/Fe 3 O 4 catalyst and then subjected to the nucleophilic attack of hydrazine hydrate with two nucleophilic sites.…”

“…An acceptable mechanism for the synthesis of 2-amino-tetrahydro-4H-chromene-3-carbonitrile derivatives is illustreated in Figure 9. According to reported articles, [43,56] the aromatic aldehyde activated by the acidic sites of catalyst and reacted with malononitrile which was activated by the basic sites of catalyst to form…”

Guanidinylated SBA-15/Fe3O4 mesoporous nanocomposite as an efficient catalyst for the synthesis of pyranopyrazole derivatives

“…The guanidinylation reaction has been used to convert primary amine groups in different materials for example chitosan 18 , 19 and Poly(2-guanidinoethylmethacrylate) 20 into guanidine groups. Multicomponent reactions (MCRs) are one of the most significant methods for the synthesis of heterocyclic compounds because of their outstanding properties such as high atomic economy, short reaction time, straightforward reaction model, high selectivity, and great compliance with principals of green chemistry 21 – 23 . Among the product of MCRs, the pyranopyrazole derivatives have received much interest of researchers due to their extensive application in pharmacology and medicine 24 – 27 .…”

Magnetized Dextrin: Eco-Friendly Effective Nanocatalyst for the Synthesis of Dihydropyrano[2,3-c]pyrazole Derivatives

“…Dihydropyrano [2,3-c]pyrazole is a heterocyclic compound with potential application in medicinal and pharmaceutical chemistry and significant role as building blocks in the preparation of valuable drugs such as antimicrobial, antiviral, analgesic, anti-inflammatory, anticancer and anti-proliferative [5]. In continues to our research on MCRs and nanomaterials [6][7][8], in present work, magnetized dextrin was used as a hybrid nanocatalyst in the synthesis of dihydropyrano [2,3-c]pyrazoles derivatives, via one-pot condensation of ethyl acetoacetate, hydrazinehydrate, malononitrile and aromatic aldehydes (scheme 1).…”