Abstract

Amino acid polyoxometalate nanoparticles-embedded microcapsules were in situ fabricated by layer-by-layer (LbL) self-assembly method [isopolyoxometalate, Mo₈O₂₆·nH₂O; amino acid, aspartic acid (AFO)]. Aspartate functionalized γ-octamolybdate (AFO) [Co₂(C₄H₆NO₄)₂(Mo₈O₂₆)(H₂O)₁₀]·4H₂Owas employed as heterogeneous catalyst for efficient, diverse, and high yielding synthesis of spirochromenes via a three-component reaction involving isatins or acenaphthenequinone, malononitrile or ethyl cyanoacetate, and various 1,3-diketones (dimedone, barbituric acid, or ethyl acetoacetate) or 4-hydroxycoumarin/3-methyl-1H-pyrazol-5(4H)-one in water/ethanol under reflux. The AFO is characterized by some physico-chemical approaches such as elemental analysis, ICP, IR, and UV–Vis spectroscopies and PXRD analyses. Notably, the heterogeneous catalyst AFO, containing molybdenum atom as the basis and appropriate redox nature, reinforced with the organic metal fragment in its structure, showed effective catalytic activity, and could be recovered simply from the reaction mixture and reused at least three runs without significant loss of its catalytic activity. This prolific combination of amino acids and isopolyoxometalates inaugurates a powerful class of porous catalysts for the different chemical transformations, which overcomes key limitations of previously established salts and Lewis acidic metals based catalysts under low catalyst loading, the use of water scavengers, dry solvents, and additives for facilitating the specialized experimental setups commonly employed to the organic reactions.

摘要

通过层层（LbL）自组装方法[异多金属氧酸盐，Mo ₈ O ₂₆ ·nH ₂ O; 氨基酸，天冬氨酸（AFO）]。天冬氨酸官能化的γ-八钼酸酯（AFO）[Co ₂（C ₄ H ₆ NO ₄）₂（Mo ₈ O ₂₆）（H ₂ O）₁₀ ]·4H ₂ O被用作非均相催化剂，以高效，多样且高产地合成螺环色素的通过三组分反应，包括靛红或or啶醌，丙二腈或氰基乙酸乙酯和各种1,3-二酮（二甲酮，巴比妥酸或乙酰乙酸乙酯）或4-羟基香豆素/ 3-甲基-1 H-吡唑-5（4 H）-在回流下的水/乙醇溶液中。AFO的特征在于一些物理化学方法，例如元素分析，ICP，IR和UV-Vis光谱分析以及PXRD分析。值得注意的是，以钼原子为基础并具有适当的氧化还原性质的非均相催化剂AFO，在其结构中被有机金属碎片增强，显示出有效的催化活性，可以简单地从反应混合物中回收并至少重复使用三遍而无明显影响。失去其催化活性。氨基酸和异多金属氧酸盐的丰富结合开创了用于不同化学转化的一类强大的多孔催化剂，它克服了先前建立的盐和路易斯酸性金属基催化剂在低催化剂负载，使用除水剂，干燥溶剂，