Rapid and Efficient Synthesis of Spiro-Oxindoles using Fe3+-Montmorillonite under Ultrasonic Irradiation

Collagen-coated superparamagnetic iron oxide nanoparticles as a sustainable catalyst for spirooxindole synthesis

In this work, a novel magnetic organic–inorganic hybrid catalyst was fabricated by encapsulating magnetite@silica (Fe₃O₄@SiO₂) nanoparticles with Isinglass protein collagen (IGPC) using epichlorohydrin (ECH) as a crosslinking agent. Characterization studies of the prepared particles were accomplished by various analytical techniques specifically, Fourier transform infrared (FTIR) analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), energy-dispersive X-ray spectroscopy (EDS), X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), and Brunauer−Emmett−Teller (BET) analysis. The XRD results showed a crystalline and amorphous phase which contribute to magnetite and isinglass respectively. Moreover, the formation of the core/shell structure had been confirmed by TEM images. The synthesized Fe₃O₄@SiO₂/ECH/IG was applied as a bifunctional heterogeneous catalyst in the synthesis of spirooxindole derivatives through the multicomponent reaction of isatin, malononitrile, and C-H acids which demonstrated its excellent catalytic properties. The advantages of this green approach were low catalyst loading, short reaction time, stability, and recyclability for at least four runs.

Synthesis of mono- and bis-spirooxindole derivatives "on water" using double salt of aluminum sulfate-sulfuric acid as a reusable catalyst

The preparation of double salt of aluminum sulfate-sulfuric acid (Al4(SO4)6·(H2SO4)·24H2O) by the reaction of aluminum sulfate and sulfuric acid in water is described. Aluminum sulfate-sulfuric acid is characterized via some spectroscopic and microscopic techniques such as infrared spectroscopy (IR), X-ray diffraction spectroscopy (XRD), energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) which corroborated the structure of the double salt. This double salt is soluble in water and insoluble in organic solvents. It was employed as a new catalyst for the synthesis of spirooxindole compounds on water with good to excellent yields. The double salt could be recycled and reused without appreciable loss of activity.

Studies on the Synthesis of Substituted 2-amino-4H-benzo[h]chromene and 3-amino-1H-benzo[f]chromene Derivatives Using Base Supported Ionic Liquid Like-phase (SILLP) as an Efficient Green Catalyst

The synthesis of several substituted 2-amino-4 H-benzo[ h]chromene and 3-amino-1 H-benzo[ f]chromene derivatives was carried out using a one-pot three-component reaction of an arylaldehyde, malononitrile and a naphthol in H2O and in the presence of recyclable base supported ionic liquid like-phase as an efficient green catalyst.

[γ-Fe2O3@HAp-SO3H] an Efficient Nanocatalyst for the Synthesis of Highly Functionalised 2-thioxopyrido[2,3-d]Pyrimidines

HAp(hydroxyapatite)-encapsulated-γ-Fe2O3 supported sulfonic acid nanoparticles were used for the preparation of two series of 2-thioxopyrido[2,3-d]pyrimidines. In the first series, 2-thioxopyrido[2,3-d]pyrimidines were synthesised from 3-(6-amino-1,2,3,4-tetrahydro-4-oxo-2-thioxopyrimidin-5-yl)-3-oxopropanenitrile and arylaldehydes in the presence of [γ-Fe2O3@HAp-SO3H] as a nanocatalyst, in high yields (84–96%). In the second series, [γ-Fe2O3@HAp-SO3H] was used to catalyse the reaction of 6-amino-2-(alkylthio)-pyrimidine-4,6(1H,5H)-dione, 1,3-diethyl-2-thioxodihydropyrimidine-4,6(1H,5H)-dione and various arylaldehydes to prepare 2-thioxo-2,3,7,10-tetrahydropyrido[2,3-d:5,6-d']dipyrimidine-4,6 (1H,5H)-diones in excellent yields (93–98%).