Recently, Fe3O4 magnetic nanoparticles (MNPs) have been extensively studied. 1–6 These nanoparticles are good support materials for heterogeneous catalysis because of their easy synthesis, high surface area, facile separation by magnetic forces, low toxicity and cost. We envisioned using MNPs for the preparation of new tacrine derivatives. Tacrine derivatives have been of interest to synthetic organic chemists because of their biological properties, such as: anti-inflammatory, anti-tumor, hepatoprotective, antiallergic, anti-HIV-1, antiviral, antifungal, antimicrobial, anti-asthmatic, anti-oxidant, antinociceptive, antidiabetic and antidepressant effects. Tacrine is the first approved acetylcholinesterase inhibitor for the treatment of Alzheimer’s disease, and it has been broadly investigated. Tacrine and its congeners can be prepared by the Friedl€ander reaction, and for this such catalysts have been used as AlCl3, 15 POCl3, 16 InCl3, 17 Lewis acids (PTSA), ZnCl2, 20 BF3 Et2O, SnCl4, CuCl, CuCl2, TiCl4 and P2O5. Although each of these catalysts may have its own merits, typical disadvantages include long reaction times, difficult removal and recovery, high cost, toxicity and low product yields. Tacrine hybrids can be produced by the reaction between the NH2 group of tacrine and other organic compounds that have proven activities. Since the tacrine derivatives have a chiral center at the CH of the pyran ring, they are racemic mixtures. Both enantiomers could be separated and investigated. We now report for the first time the preparation of a novel magnetic Fe3O4/silica nanoparticle-supported L-methionine (Fe3O4@SiO2@L-methionine@Ni (II)) catalyst (Scheme 1). We have fully characterized the new catalyst and have evaluated its catalytic activity. We had previously reported the synthesis of pyrano [2, 3-c] pyrazole derivatives in good yield, by the reactions of aryl aldehydes, hydrazine hydrate, ethyl benzoylacetate and malonitrile in the presence of choline chloride based thiourea (ChCl 2thiourea) as homogeneous catalyst (Scheme 2).

中文翻译：

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Ni (II) 固定在 Fe3O4@SiO2@L-甲硫氨酸上：一种可重复使用的纳米催化剂及其在合成新四环他克林衍生物中的应用

最近，Fe3O4 磁性纳米粒子（MNPs）得到了广泛的研究。1-6 这些纳米粒子由于易于合成、表面积大、磁力分离容易、毒性低且成本低，是多相催化的良好支撑材料。我们设想使用 MNP 来制备新的他克林衍生物。他克林衍生物因其生物学特性而受到合成有机化学家的关注，例如：抗炎、抗肿瘤、保肝、抗过敏、抗 HIV-1、抗病毒、抗真菌、抗微生物、抗哮喘、抗氧化, 镇痛、抗糖尿病和抗抑郁作用。他克林是首个获批用于治疗阿尔茨海默病的乙酰胆碱酯酶抑制剂，并已得到广泛研究。他克林及其同系物可以通过弗里德兰德反应制备，为此这类催化剂已被用作 AlCl3、15 POCl3、16 InCl3、17 路易斯酸 (PTSA)、ZnCl2、20 BF3 Et2O、SnCl4、CuCl、CuCl2、 TiCl4 和 P2O5。虽然这些催化剂中的每一种都有其自身的优点，但典型的缺点包括反应时间长、难以去除和回收、成本高、毒性和产品收率低。他克林杂化物可以通过他克林的 NH2 基团与其他已证实活性的有机化合物之间的反应产生。由于他克林衍生物在吡喃环的 CH 处具有手性中心，因此它们是外消旋混合物。可以分离和研究两种对映异构体。我们现在首次报道了一种新型磁性 Fe3O4/二氧化硅纳米颗粒负载的 L-甲硫氨酸（Fe3O4@SiO2@L-甲硫氨酸@Ni（II））催化剂的制备（方案 1）。我们已经充分表征了新催化剂并评估了其催化活性。我们之前曾报道过芳醛、水合肼、苯甲酰乙酸乙酯和丙腈在氯化胆碱基硫脲（ChCl 2 硫脲）作为均相催化剂存在下的反应，以良好的收率合成吡喃并 [2, 3-c] 吡唑衍生物（方案2）。