Sulfuric acid functionalized silica-coated magnetic nanoparticles (SSA-MNPs) were prepared by a simple method and evaluated as efficient catalysts for the condensation reaction of 6-amino-1,3-dimethyluracil with mono-, di-, or trialdehydes to give the corresponding mono-, di-and tri[bis(6-aminopyrimidinyl)methanes]. The catalyst was simply recycled by the use of an external magnetic field and could be reused five times without significant loss of activity or mass.

Alkanedisulfamic acid-functionalized silica-coated magnetic nanoparticles (ADSA-MNPs) were prepared by a simple method and evaluated as efficient catalysts for the preparation of mono-, bis-, and tris[bis(4-hydroxycoumarinyl)methanes] through condensation of 4-hydroxy-2H-coumarin-2-one with mono-, di-, or trialdehydes, respectively. The heterogeneous nanocatalyst was readily recovered from the reaction mixture by using external magnet and was reused five times without significant loss of catalytic activity.Acid-functionalized silica-coated magnetic nanoparticles have recently emerged as attractive supports for immobilization of homogeneous catalysts. Various acid-functionalized silica-coated magnetic nanoparticles have been prepared and used as efficient catalysts for a range of organic transformations, such as deprotection of benzaldehyde dimethylacetals 1 and the synthesis of α-amino nitriles; 2 mono-, bis-, and tris[bis(6-aminopyrimidinyl)methanes]; 3 quinolines; 4 benzo[a]xanthenone derivatives; 5 and aminoimidazopyridine skeletons. 6 Coumarin derivatives have received considerable attention because of their useful pharmacological activities. 4-Hydroxycoumarin derivatives have attracted particular attention because of their useful biological and pharmacological properties, such as anticoagulant, 7 spasmolytic, 8 and rodenticidal activities. 9 Coumarins in general, and biscoumarins in particular, exhibit antifungal, anti-HIV, anticancer, antithrombotic, antimicrobial, antioxidant 10,11 urease-inhibitory, 12 cytotoxic, and enzyme inhibitory activities. 13 As a result, the synthesis of this class of compounds is very important. The reaction of 4-hydroxycoumarin with aldehydes affords the corresponding bis(4-hydroxycoumarinyl)methanes, a useful class of organic compounds. This reaction is catalyzed by ruthenium(III) chloride hydrate, 14 piperidine, 12 sulfated titania, 15 iodine, 16 or a poly(4-vinylpyridinium butylsulfonate)-supported catalyst. 17 Although the known procedures for the synthesis of corresponding bis(4-hydroxycoumarinyl)methanes have their merits, they also suffer from some drawbacks, such as low yields, prolonged reaction times, the use of costly reagents or catalysts, or the use of toxic organic solvents. The recovery of the catalyst can also be a problem. Although the reaction of 4-hydroxycoumarin with monoaldehydes has been investigated, [11][12][13][14][15][16][17][18][19] there have been no reports on reactions of 4-hydroxycoumarin with di-or trialdehydes for the synthesis of bis-and tris[bis(4-hydroxycoumarinyl)methanes], respectively. As a continuation of our research on the preparation and catalytic investigation of new acid-functionalized magnetic nanoparticles, 3,20 we synthesized new alkanedisulfamic acid magnetic nanoparticles (ADSA-MNPs) by direct reaction of chlorosulfonic acid with diaminoalkylsilicacoated magnetic nanoparticles (Scheme 1), and we used these nanoparticles as a catalyst system for the synthesis of mono-, bis-, and tris[bis(4-hydroxycoumarinyl)methanes] by condensa...

Facile solution method for the synthesis of tri-arm star shaped 1,3,5-triazines was developed using 1,5,7-Triazabicyclo[4.4.0]dec-5-ene (TBD) by reaction of cyanuric chloride with O-nucleophiles.

Novel magnetite-sulfuric acid (Fe 3 O 4 ·SO 3 H) magnetic nanoparticles were prepared by the direct reaction of chlorosulfonic acid with magnetite nanoparticles, and characterized by IR spectroscopy, thermogravimetric analysis, X-ray diffraction, and scanning electron microscopy. The catalytic activity of the Fe 3 O 4 ·SO 3 H nanoparticles in the reaction of 2-naphthol with aryl mono-, di-and trialdehydes was examined, and these catalysts were shown to exhibit remarkable catalytic performance in the solvent-free synthesis of mono-, bis-, and tris-14H-dibenzo[a,j]xanthen-14-ylarenes. The catalyst retained its activity for several cycles.

Silica sulfuric acid magnetic nanoparticles efficiently catalyze the one-pot, three-component reaction of isatins and malononitrile with dimedone, 1,3-dimethylbarbituric acid or 4-hydroxycoumarin in EtOH–H2O to afford the corresponding spiro[2-amino-4H-pyran-oxindole] derivatives in high yields under ultrasound irradiation at 60 °C. The heterogeneous nanocatalyst could be recovered easily from the reaction mixture using an external magnet and reused many times without significant loss of its catalytic activity.