Efficient synthesis of 3,3′-bisindoles catalyzed by Fe3O4@MCM-48-OSO3H magnetic core-shell nanoparticles

SO3H-Functionalized Epoxy-Immobilized Fe3O4 Core-Shell Magnetic Nanoparticles as an Efficient, Reusable, and Eco-Friendly Catalyst for the Sustainable and Green Synthesis of Pyran and Pyrrolidinone Derivatives

A SO₃H-functionalized epoxy-immobilized Fe₃O₄ core-shell magnetic nanocatalyst was prepared through a simple three-step procedure, and it was identified by various analyses such as Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), differential thermal gravity (DTG), Brunauer-Emmett-Teller (BET) analysis, transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), thermogravimetric analysis (TGA), vibration sample magnetometry (VSM), and powder X-ray diffraction (PXRD). BET analysis showed that the as-prepared nanocatalyst was synthesized with a mesoporous structure and high specific area (35.45 m² g^-1). The TEM image clearly showed that the particle size distribution was in the range of 47-65 nm. The designed magnetic nanocatalyst was used successfully in the synthesis of pyran derivatives via the reaction of dimedone, malononitrile, and various aromatic aldehydes and synthesis of pyrrolidinone derivatives via the reaction of various aromatic aldehydes, aniline, and diethyl acetylenedicarboxylate. The nanocatalyst was simply isolated from the reaction mixture utilizing an external magnet and reused several times according to the model reactions without significant loss in its efficiency.

Efficient one-pot synthesis and dehydrogenation of tricyclic dihydropyrimidines catalyzed by OMS-2-SO3H, and application of the functional-chromophore products as colorimetric chemosensors

An efficient and convenient one-pot multicomponent reaction (MCR) for the synthesis and dehydrogenation of tricyclic dihydropyrimidine derivatives, catalyzed by –SO₃H functionalized octahedral manganese oxide molecular sieves (OMS-2-SO₃H) as a novel solid acid catalyst, is reported. All of the organic products and the catalyst were unambiguously characterized with conventional techniques including Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction analysis (XRD), ¹H NMR, and ¹³C NMR spectroscopy. The targeted dehydrogenated chromophore compounds were successfully used as colorimetric chemosensors for detection of transition metals in aqueous solution. For example, 1-[4-(4-hydroxy-3-methoxy-phenyl)-2-methyl-benzo[4,5]imidazo[1,2-a]pyrimidin-3-yl]-ethanone (7d), exhibited high sensitivity and selectivity toward detection of Cr³⁺ over a panel of other transition metal cations. The interference of foreign ions was found to be negligible. It was found that a 1 : 1 complex of Cr³⁺ and 7d is responsible for the color change of the solution from ochre to brown. These newly devised chemosensors can also exhibit significant wavelength shifts (up to 100 nm) when used as pH indicators. 7d for example, showed a vivid and sharp color change from pink to yellow in the pH range of 4 to 6.

Hyperconjugated products of dihydropyrimidines may act as colorimetric chemosensors.

Magnetic iron oxide/phenylsulfonic acid: A novel, efficient and recoverable nanocatalyst for green synthesis of tetrahydrobenzo[b]pyrans under ultrasonic conditions

A novel magnetic iron oxide supported phenylsulfonic acid (Fe₃O₄@Ph-SO₃H) with core-shell structure is prepared, characterized and applied as efficient nanocatalyst for green synthesis of tetrahydrobenzo[b]pyrans. The Fe₃O₄@Ph-SO₃H was prepared via modification of magnetic iron oxide cores with 1,4-bis(triethoxysilyl)benzene (BTEB) followed by sulfonation of aromatic rings. The Fe₃O₄@Ph-SO₃H was characterized using FTIR, TGA, PXRD, SEM, TEM, VSM and EDX techniques. This was effectively applied for synthesis of tetrahydrobenzo[b]pyrans in water as green solvent at room temperature under ultrasonic conditions. The products were obtained in high to excellent yields at short times. The recoverability, reusability and durability of this nanocatalyst were studied under applied reaction conditions.