Superparamagnetic nanoparticles of modified vitamin B3 (Fe3O4@Niacin) represent a new, efficient and green biocatalyst for the one‐pot synthesis of 2‐amino‐3‐cyanopyridine derivatives via four‐component condensation reaction between aldehydes, ketones, malononitrile, and ammonium acetate under microwave irradiation in water. This new magnetic organocatalyst was easily isolated from the reaction mixture by magnetic decantation using an external magnet and reused at least six times without significant degradation in the activity. The catalyst was fully characterized by FT‐IR, XRD, SEM, VSM, UV–Vis, DLS and EDS. Excellent yield, very short reaction time (7–10 min), operational simplicity, easy work‐up procedure, avoidance of hazardous or toxic catalysts and organic solvents are the main advantages of this green methodology which makes it more economic than the other conventional methods.

Synthesis, characterization and utilization of the l-proline N-sulfonic acid-functionalized magnetic nanoparticles as a novel magnetically reusable acid catalyst for the synthesis of 3,4-dihydropyrimidine-2-[1H]thione derivatives is reported.

Thiazolopyrimidine derivatives are well known because of their excellent therapeutic properties. In this investigation, an effective one‐pot three‐component method is described for the synthesis of novel 2‐[(Z)‐1‐(substituted phenyl)methylidine]‐7‐methyl‐3‐oxo‐5‐(substituted phenyl)‐2,3‐dihydro‐5H‐thiazolo[3,2‐a]pyrimidine‐6‐carboxilic acid tert‐butyl ester derivatives by condensation reaction of 3,4‐dihydropyrimidine‐2(1H)‐thiones, various aromatic aldehydes and chloroacetyl chloride under reflux conditions in the presence of Fe3O4@l‐arginine nanoparticles as a magnetically reusable and eco‐friendly catalyst with short reaction times and moderate yields. The chemical structures of all synthesized compounds were determined using infrared, 1H NMR and 13C NMR spectroscopies. In vitro antimicrobial activities of 3,4‐dihydropyrimidine‐2(1H)‐thiones and newly fused thiazolo[3,2‐a]pyrimidine derivatives were examined using the well diffusion method against diverse pathogenic strains, namely Staphylococcus aureus ATCC 6538, S. epidermidis ATCC 12228, Escherichia coli ATCC 8739 and Pseudomonas aeruginosa ATCC 9027 (bacteria), Candida albicans ATCC 10231 (yeast) and Aspergillus niger ATCC 16404 (fungus). The compounds having 2‐hydroxy, 4‐hydroxy, 2‐chloro and 4‐chloro groups attached to the phenyl ring on the pyrimidine and 4‐CH3, 4‐OCH3 and 3‐NO2 groups attached to benzylidine on the thiazolo moiety showed significant antibacterial activity.

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