Preparation Of Magnietic Nanoparticles And Their Application In Organic Synthesis

The isolation and separation of nanocatalysts can be achieved using magneticallyseparable nanoparticles (MSNPs). They offer a promising option that can meet therequirements of high accessibility with improved reusability. One of the most attractivefeatures of MSNPs is their separation properties. Catalyst recovery and reuse are the two mostimportant features for many catalytic processes, and most heterogeneous systems require afiltration or centrifugation step and/or a tedious workup of the final reaction mixture torecover the catalyst. However, magnetically supported catalysts can be recovered with anexternal magnet due to the paramagnetic character of the support, resulting in remarkablecatalyst recovery without the need for a filtration step; the catalysts can be subsequentlyreused in another cycle. Magnetically separable catalysts (MSC) also offer importantactivities in a wide range of reactions due to their potential for designed surfacefunctionalities along with catalyst preparation.A novel, environmentally friendly procedure has been developed for the preparation ofsecondary or tertiary amines by one-pot reductive amination of carbonyl compounds usingsodium borohydride in the presence of a magnetically recoverable sulfonic acid supported onhydroxyapatite-encapsulated-γ-Fe2O3[γ-Fe2O3@HAP-SO3H] at room temperature. Thecatalyst was easily separated from the reaction mixture by applying an external magnet andreused for six cycles without significant loss of catalytic activity.Nano magnetically silica-supported dodecyl benzenesulfonic acid([γ-Fe2O3@SiO2-DDBSA]) was readily prepared and identified as an efficient catalyst for thesynthesis of spirooxindole-pyrimidine derivatives by three-component condensation reactionof barbituric acids, isatins and cyclohexane-1,3-diones. The aqueous reaction medium, easyrecovery of the catalyst using an external magnet, and high yields make the protocolsustainable and economic.