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چکیده
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Compounds containing a chiral oxazoline ring have become one of the most successful, versatile, and commonly used classes of ligands for asymmetric catalysis due to their ready accessibility, modular nature, and applicability in a wide range of metal-catalyzed transformations. However, these catalysts require high catalyst-to-substrate ratio to achieve high enantioselectivity and high turnover frequency (TOF). Therefore, there is a great deal of interest to immobilize these catalysts on mesoporous silicas such as MCM-41 and SBA-15 [1-2]. We herein report the design and development of a recyclable heterogeneous catalyst for the asymmetric henry reaction (AHR) [3] to afford chiral nitro alcohols in good to excellent yields and enantioselectivities for the first time (Scheme 1). For this purpose, at first, novel bidentate oxazoline ligands were synthesized and then these ligands immobilized on MCM-41 and SBA-15 mesoporous porous silicas. After that, the resulting heterogeneous catalysts were utilized in asymmetric henry reaction. The nitro groups of these products were reduced to amino group, or nucleophilic displacement.
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