a general and inexpensive protocol for the nanomagnetic 5-sulfosalicylic acid catalyzed the synthesis of tetrahydrobenzo[b]pyrans and quinoxaline derivatives

In this study, a novel acid-functionalized magnetic nanoparticles with high loaded multifunctional acidic groups was fabricated by anchoring water-soluble 5-sulfosalicylic acid onto the surface silica-modified fe3o4. the magnetically recyclable fe3o4@sio2@5-sa (20 mg) showed excellent reactivity for greener synthesis of tetrahydrobenzo[b]pyrans via a three-component reaction of different aromatic aldehydes, malononitrile and dimedone in good to excellent yields (70–95%) in pure water at short reaction times (40–150 min). the method shows eco-friendly synthesis of quinoxaline derivatives from direct condensation of substituted 1,2-diamine with various 1,2-dicarbonyl in ethanol at room temperature to afford the desired quinoxalines with good to excellent yields (60–97%) at shorter reaction times (120–240 min). the morphology and magnetic properties of mnps were studied with scanning electron microscopy, x-ray powder diffraction, fourier translation infrared spectroscopy, vibrating sample magnetometer and thermogravimetric. the results showed that the fe3o4@sio2@5-sa catalyst is completely recoverable by an external magnet and retained catalytic activity after five recycles.