Silica sulfuric acid-coated Fe 3 O 4 nanoparticles as high reusable nanocatalyst for the oxidation of sulfides into sulfoxides, protection and deprotection of hydroxyl groups using HMDS and Ac 2 O

Magnetic Fe3O4 nanoparticles supported imine/Thiophene‐nickel (II) complex: A new and highly active heterogeneous catalyst for the synthesis of polyhydroquinolines and 2, 3‐dihydroquinazoline‐4(1H)‐ones

“…Then the products (Fe 3 O 4 @SiO 2 ) were isolated with an external magnet and washed two times with ethanol and distilled water. [35] …”

“…Silica-coated magnetic Fe 3 O 4 nanoparticles (Fe 3 O 4 @SiO 2 ) were prepared by chemical co-precipitation strategy. [35] The Fe 3 O 4 @SiO 2 -propyl chloride was prepared by the reaction of Fe 3 O 4 @SiO 2 with 3-aminopropyltrimethoxysilane (APTMS) in thermal EtOH/ H 2 O for 8 h. [5] Next, the imine bond was formed through the condensation between Fe 3 O 4 @SiO 2 -propyl amine with thiophene-2-carbaldehyde in refluxing ethanol under nitrogen conditions. Ultimately, the Imine/Thiophene- The morphology and size of the nickel nano-solid was investigated by Scanning electron microscope (SEM) as shown in Figure 2 The SEM image of Ni(NO 3 ) 2− Imine/Thiophene-Fe 3 O 4 @SiO 2 shows that the catalyst is formed of nanometre-sized particles.…”

Magnetic Fe3O4@silica sulfuric acid nanoparticles promoted regioselective protection/deprotection of alcohols with dihydropyran under solvent-free conditions

“…Owing to the unique properties of magnetic nanoparticles, sulphuric acid adsorbed on silica coating MNPs core-shell structures (Fe 3 O 4 @SiO 2 @-SO 3 H) have been utilized as a catalyst in various organic transformations, such as Biginelli reaction, 16 synthesis of amidoalkyl naphthols 17 and protection-deprotection of hydroxyl groups using hexamethyldisilazane (HMDS). 18 In this communication, we report tetrahydropyranylation/depyranylation of alcohols with sulphuric acid adsorbed on a silica coating MNPs core-shell structure under solvent-free conditions, which makes it free from the hazardous effects of organic toxic solvents, offering a green and eco-friendly approach.…”

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“…The catalyst was easily separated with the assistance of an external magnetic field from the reaction mixture and reused for several consecutive runs without significant loss of its catalytic efficiency. 28 The catalytic activity of dopamine sulfamic acid-functionalized magnetic Fe 3 O 4 nanoparticles (DSA@MNPs) was evaluated in the oxidation of sulfides to the sulfoxides. The structure of asprepared catalyst was characterized by a series of spectroscopic techniques such as XRD, FT-IR, TGA, SEM, VSM, TEM and EDX.…”