纳米尺度NiLa_2O_4尖晶石催化NaBH_4还原亚胺制仲胺（英文）

Nano-sized NiLa_2O_4 spinel–NaBH_4-mediated reduction of imines to secondary amines

由溶胶-凝胶法制得的Ni-La化合物经热分解制备了纳米尺度NiLa2O4尖晶石,在750o C焙烧后形成了结晶良好的尖晶石结构.采用差热分析、X射线衍射、透射电镜、扫描电镜和粒度分布分析等手段表征了该尖晶石的物理化学性质.结果表明,该纳米颗粒有规则的外形和确定的晶面,由平均粒径为40 nm的规整半球晶粒组成.精修的晶胞参数a=3.861205和c=12.6793.在NaBH4选择还原亚胺制相应仲胺的反应中,该新型纳米NiLa2O4尖晶石可用作高效多相催化剂,得到了较高的产物产率.所有反应可在室温和相对较短的时间内完成.在优化的反应条件下,均可得到带有不同芳基的,包括带有吸电子和供电子基团的仲胺.该催化剂回收简便,重复使用4次,其催化活性未见明显下降.

Nano-sized NiLa2O4 spinel was produced by thermal decomposition of Ni–La compounds via a sol-gel method. The well-crystallized spinel structure was formed after calcination at 750 ＆#176;C. The physicochemical properties of the spinel were investigated using differential thermal analysis, X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and particle size dis-tribution analysis. The results show that the nanoparticles have regular shapes with well-defined crystal faces and consist of uniform quasi-spherical crystallites of average size 40 nm. The refined unit cell parameters are a=3.861205 A and c=12.6793 A. This new nano-sized NiLa2O4 spinel is an efficient heterogeneous catalyst for the selective conversion of imines to the corresponding second-ary amines in the presence of NaBH4 as a reducing agent, in good to excellent yields. All the reac-tions were completely chemoselective at room temperature and had relatively short reaction times. Secondary amines with different aryl groups, including those bearing electron-withdrawing or electron-donating groups, were obtained under the optimum reaction conditions. The catalyst was readily recovered and was recycled four times with no significant loss of catalytic activity.