Abstract

Palladium nanoparticles (~ 1–3 nm, 0.4 wt% Pd) were uniformly distributed over the surface of fibrous silica nanospheres (KCC-1) modified via aminopropyltriethoxysilane using a fast and cost-effective palladium (II) chloride reduction process. The Pd nanoparticles (Pd NPs) distribution over the ensuing catalyst Pd/KCC-1-NH₂ showed much more uniform distribution, and smaller size compared with the tedious hydrothermal reduction method. The morphological, chemical, and size analyses of Pd/KCC-1-NH₂ by BET, UV–Vis spectra, XRD, HR-TEM, EDS and XPS analysis revealed that the succeeding material consist of a distinct fibrous silica nanospheres support adorn with Pd NPs. The resultant nanocatalyst was tested for the one-step reductive aminoformylation of aromatic nitro compounds using formic acid. A wide range of substituted nitroarenes including electron withdrawing, releasing, sterically hindered and multifunctional groups have been converted to corresponding aryl formamide in quantitative yields (yields up to 98%) at moderate temperature (70 °C). Optimization study has proved that the 6 equivalent of formic acid is required and toluene was found to be the better solvent. The established practice is beneficial due to the use of formic acid as H₂ source and formylating agent, easiness in handling of the catalyst and simple workup procedure with efficient catalyst reusability.

Graphic abstract

中文翻译：

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利用纤维结构二氧化硅纳米球辅助的钯纳米粒子对硝基芳烃进行有效和选择性的直接氨基甲酰化

摘要

钯纳米粒子（〜1-3 nm，0.4 wt％Pd）均匀分布在通过氨基丙基三乙氧基硅烷改性的纤维状二氧化硅纳米球（KCC-1）的表面上，采用快速且经济高效的氯化钯（II）还原工艺。与乏味的水热还原法相比，Pd纳米粒子（Pd NPs）在随后的催化剂Pd / KCC-1-NH _2上的分布显示出更均匀的分布，并且尺寸更小。Pd / KCC-1-NH ₂的形态，化学和尺寸分析通过BET的UV-Vis光谱，XRD，HR-TEM，EDS和XPS分析表明，后续材料由装饰有Pd NP的独特的纤维状二氧化硅纳米球组成。测试所得纳米催化剂使用甲酸进行的芳族硝基化合物的一步还原性氨基甲酰化。在中等温度（70°C）下，大量取代的硝基芳烃（包括吸电子，释放，空间受阻和多官能团）已以定量收率（最高收率98％）转化为相应的芳基甲酰胺。优化研究证明需要6当量的甲酸，并且发现甲苯是更好的溶剂。由于使用甲酸作为H ₂，已建立的实践是有益的 源和甲酰化剂，易于处理催化剂，后处理步骤简单，催化剂可有效重复使用。

图形摘要