The multicomponent Mannich reaction is one of the most important carbon-carbon bond formation types in organic chemistry and plays a key step in the synthesis of many nitrogen-containing natural products and pharmaceuticals. Mannich bases have a very important place in the synthesis of anti-inflammatory, antimicrobial, antimalarial, and anticancer drugs. They are used in the petroleum, paper and recycling industries. Several methods have been reported in the literature for the synthesis of b-amino carbonyl compounds using Amberlyst-15, Br€onsted acids, Lewis acids and bases. However; these methods have some drawbacks, including the use of expensive metal salts as catalysts. In view of these findings, we wanted to broaden the possibility of iodine as the catalyst for the synthesis of b-amino carbonyl compounds. In this work, we describe a mild, convenient, efficient and one-pot method for preparation of b-amino carbonyl compounds, using molecular iodine as a catalyst at room temperature, from ketones, aromatic aldehydes, and aromatic amines (Scheme 1). The synthesized b-amino carbonyl compounds (4a-o) were purified by crystallization or column chromatography and were characterized by elemental analysis, IR, H NMR, C NMR, and GC-MS methods. A number of these compounds (4f-i, 4k-n) are novel. All of the compounds were evaluated for their antioxidant activity using the 1,1diphenyl-2-picryl-hydrazyl (DPPH) assay. The Mannich reaction of aniline, benzaldehyde and cyclohexyl methyl ketone was selected as a model and several catalysts have been tried (Table 1). The highest yield was obtained with I2 (Table 1, entry 2). In preliminary trials, several common organic solvents (acetone, ethanol, THF, toluene, and DCM) had been used to optimize the reaction conditions. Ethanol was found to be the most suitable solvent for the reaction in terms of availability, cost, and over-all yield. Different molar ratios of iodine catalyst were investigated to find the best yield. The optimum value was 10mol % of I2 catalyst (Table 2).

中文翻译：

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碘催化三组分曼尼希反应的β-氨基羰基化合物及其抗氧化活性评价

多组分曼尼希反应是有机化学中最重要的碳-碳键形成类型之一，在许多含氮天然产物和药物的合成中起着关键作用。曼尼希碱在抗炎、抗微生物、抗疟和抗癌药物的合成中具有非常重要的地位。它们用于石油、造纸和回收行业。文献中报道了几种使用 Amberlyst-15、布朗斯台德酸、路易斯酸和碱合成 b-氨基羰基化合物的方法。然而; 这些方法有一些缺点，包括使用昂贵的金属盐作为催化剂。鉴于这些发现，我们希望扩大碘作为合成 b-氨基羰基化合物催化剂的可能性。在这项工作中，我们描述了一种温和的，在室温下使用分子碘作为催化剂，从酮、芳香醛和芳香胺制备 b-氨基羰基化合物的方便、高效和一锅法（方案 1）。合成的b-氨基羰基化合物(4a-o)通过结晶或柱色谱纯化，并通过元素分析、IR、H NMR、C NMR和GC-MS方法表征。许多这些化合物 (4f-i, 4k-n) 是新的。使用 1,1-二苯基-2-苦基-肼 (DPPH) 测定法评估所有化合物的抗氧化活性。选择苯胺、苯甲醛和环己基甲基酮的曼尼希反应作为模型，并尝试了几种催化剂（表 1）。I2 获得的产量最高（表 1，条目 2）。在初步试验中，几种常见的有机溶剂（丙酮、乙醇、THF、甲苯和 DCM) 已用于优化反应条件。就可用性、成本和总产率而言，发现乙醇是最适合该反应的溶剂。研究了不同摩尔比的碘催化剂以找到最佳产率。最佳值为 10mol% 的 I2 催化剂（表 2）。