In this study, an efficient and novel procedure has been reported for loading sulfanilic acid on the surface of magnetite Fe3O4 nanoparticles using tris(hydroxymethyl) aminomethane and 1,2-dichloroethane. Next, the synthesized nanocatalyst was fully characterized using FT-IR, XRD, TGA, VSM, SEM, and TEM. The results show that the synthesis of magnetic nanocatalyst has been successful with a range of 2–20 nm in size. Finally, the catalytic activity of this superparamagnetic nanocatalyst was explored for the synthesis of tetrahydrobenzo[b]pyran and 2-amino-5-oxo-4,5-dihydropyrano[3,2-c]chromene-3-carbonitrile derivatives. The synthesized nanocatalyst has advantages such as non-toxicity, short reaction time, easy workup, cleaner reaction profiles under mild reaction conditions.

Preparation and characterization of MNPs–PhSO 3 H as a heterogeneous catalyst for the synthesis of benzo[ b ]pyran and pyrano[3,2- c ]chromenes

Ionic liquids (ILs) and deep eutectic solvents (DESs) debuted with a promise of a superior sustainability footprint due to their low vapor pressure. However, their toxicity and high cost compromise this footprint, impeding their real-world applications. Fortunately, their property tunability through a rational selection of precursors, including bioderived ones, provides a strategy to ameliorate toxicity, lower cost and endow new functions. This review addresses whether ILs and DESs are sustainable solvents or contribute to sustainable chemical processes.

Enabling Sustainable Chemistry with Ionic Liquids and Deep Eutectic Solvents: a Fad or the Future?

A new fluorescent sensor 5 based on a fused imidazopyridine scaffold has been designed and synthesized via cascade cyclization. The reaction features the formation of three different C–N bonds in sequence. Imidazopyridine based fluorescent probe 5 exhibits highly sensitive and selective fluorescent sensing for Fe3+(‘turn-on’) and Hg2+(‘turn-off’). The excellent selectivity of imidazopyridine for Fe3+/Hg2+ was not hampered in the presence of any of the competing cations. The limit of detection (LOD) of 5 toward Fe3+ and Hg2+ has been estimated to be 4.0 ppb and 1.0 ppb, respectively, with a good linear relationship (R2 = 0.99). Notably, 5 selectively detects Fe3+/Hg2+ through fluorescence enhancement signalling both in vitro and in HeLa cells.

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Development of a fused imidazo[1,2-a]pyridine based fluorescent probe for Fe3+ and Hg2+ in aqueous media and HeLa cells

Recent advancements in applications of ionic liquids in synthetic construction of heterocyclic scaffolds: A spotlight

The nano-sized particles enhance the exposed surface area of the active part of the catalyst, thereby increasing the contact between precursors and catalyst considerably. In this study, nano-SiO2/1,5-diazabicyclo[4.3.0]non-5-en was synthesized, characterized and used as a heterogeneous nanocatalyst for the synthesis of tetrahydrobenzo[b]pyran derivatives. Fourier Transform Infrared Spectroscopy, Field Emission Scanning Electron Microscopy, Brunauer–Emmett–Teller plot, Energy Dispersive X-ray Spectroscopy and Thermo Gravimetric Analysis were used to discern nano-SiO2/1,5-diazabicyclo[4.3.0]non-5-en. Tetrahydrobenzo[b]pyrans were synthesized by using nano-SiO2/1,5-diazabicyclo[4.3.0]non-5-en via one-pot three-component condensation of malononitrile, aldehydes and dimedone in H2O/EtOH at 60 °C. The results indicate that tetrahydrobenzo[b]pyrans were synthesized in good to high yields and short reaction times. The fundamental privileges of this method are short reaction time, plain procedure, recyclability of catalyst and high yields of products.

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Nano-SiO2/DBN: an efficacious and reusable catalyst for one-pot synthesis of tetrahydrobenzo[b]pyran derivatives

In this study, a saccharine-based ionic liquid [Bmim]Sac has been found to be a sustainable catalyst for the synthesis of 3,4-dihydropyrano[c]chromenes, 4,5-dihydropyrano[4,3-b]pyran and tetrahydrobenzo[b]pyrans scaffolds through Domino Knoevenagel–Michael reaction. The easy recovery of the catalyst and high yield of the products make the protocol attractive, sustainable and economical. A mechanistic hypothesis is discussed using the concept of cooperative catalysis based on the dual (electrophilic/nucleophilic) activation of reactants by [Bmim]Sac. Furthermore, dual hydrogen bonding of saccharinate anions plays an important role in the activation of nucleophiles.

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Anion–cation co-operative catalysis by artificial sweetener saccharine-based ionic liquid for sustainable synthesis of 3,4-dihydropyrano[ c ]chromenes, 4,5-dihydropyrano[4,3- b ]pyran and tetrahydrobenzo[ b ]pyrans in aqueous medium

An artificial sugar saccharine based anion-functionalized ionic liquid [Bmim]Sac was synthesized and used for new and straightforward strategies for the construction of a diverse range of bis-enols. The advantage of this methodology is the use of a non-toxic, inexpensive and reusable catalyst, and high atom economy and easy purification make this an efficient process. Besides, a probable mechanism describing dual activation of the ionic liquid as well as dual hydrogen bonding of the saccharinate anion has been proposed.

Himani Sharma

Papers

Anion–cation co-operative catalysis by artificial sweetener saccharine-based ionic liquid for sustainable synthesis of 3,4-dihydropyrano[ c ]chromenes, 4,5-dihydropyrano[4,3- b ]pyran and tetrahydrobenzo[ b ]pyrans in aqueous medium

Anion functionalized ionic liquid from artificial sugar: a sustainable pathway for diverse bis-enol derivatives