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چکیده
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Azalactones, or 2,4-substituted oxazolin-5-ones and their derivatives have been used in a wide variety of reactions as precursors for the synthesis of various bioactive molecules and show a wide range of pharmaceutical properties [1]. They are usually obtained by condensation reactions of different arylaldehydes with hippuric acid in acetic anhydride, in the presence of anhydrous sodium acetate as a basic catalyst, according to the Erlenmeyer method [2]. Although several methods [3-5] for the synthesis of azlactones have been reported, there is still a demand for simple and facile methodologies for the preparation of azlactones using a cheap and readily available catalyst. Nanoparticles-supported catalysts mimic their homogeneous counterparts and can be considered as ‘soluble’ analogues since they are readily dispersed and exhibit an intrinsically high surface area, attribute that allow excellent accessibility of substrates to the surface bound active catalytic sites. In the present work, a novel 2-aminopyridine-functionalized SiO2 nanoparticles was developed as a reusable heterogeneous catalyst for the synthesis of azlactone derivatives from condensation reaction of hippuric acid and aldehydes (Scheme 1). A wide variety of aromatic aldehydes, containing both electron withdrawing and donating substitutes were treated and afforded the corresponding azlactones in good to high yields. Additionally, the catalyst was reused six times without significant degradation in catalytic activity and performance.
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