Dipartimento di Scienza e Tecnologia del Farmaco and NIS-Centre for Nanostructured Interfaces and Surfaces, University of Turin, Via Giuria 9, 10125 Turin, Italy.
Dipartimento di Chimica, University of Turin, Via P. Giuria 7, 10125 Turin, Italy.
Molecules. 2020 Jan 19;25(2):410. doi: 10.3390/molecules25020410.
The optimization of sustainable protocols for reductive amination has been a lingering challenge in green synthesis. In this context, a comparative study of different metal-loaded cross-linked cyclodextrins (CDs) were examined for the microwave (MW)-assisted reductive amination of aldehydes and ketones using either H or formic acid as a hydrogen source. The Pd/Cu heterogeneous nanocatalyst based on Pd (II) and Cu (I) salts embedded in a β-CD network was the most efficient in terms of yield and selectivity attained. In addition, the polymeric cross-linking avoided metal leaching, thus enhancing the process sustainability; good yields were realized using benzylamine under H. These interesting findings were then applied to the MW-assisted one-pot synthesis of secondary amines via a tandem reductive amination of benzaldehyde with nitroaromatics under H pressure. The formation of a CuPd alloy under reaction conditions was discerned, and a synergic effect due to the cooperation between Cu and Pd has been hypothesized. During the reaction, the system worked as a bifunctional nanocatalyst wherein the Pd sites facilitate the reduction of nitro compounds, while the Cu species promote the subsequent imine hydrogenation affording structurally diverse secondary amines with high yields.
在绿色合成中，优化可持续的还原胺化协议一直是一个悬而未决的挑战。在这种情况下，研究了不同负载金属的交联环糊精（CD）在微波（MW）辅助下使用 H 或甲酸作为氢源还原胺化醛和酮的情况。基于 Pd（II）和 Cu（I）盐嵌入β-CD 网络的 Pd/Cu 多相纳米催化剂在产率和选择性方面的效果最佳。此外，聚合交联避免了金属浸出，从而提高了过程的可持续性；在 H 下使用苄胺时，可实现良好的产率。这些有趣的发现随后应用于 MW 辅助一锅法合成仲胺，通过 H 压力下苯甲醛与硝基芳烃的串联还原胺化。在反应条件下可以辨别出 CuPd 合金的形成，并假设了由于 Cu 和 Pd 之间的协同作用而产生的协同效应。在反应过程中，该体系作为双功能纳米催化剂，其中 Pd 位促进硝基化合物的还原，而 Cu 物种促进随后的亚胺加氢，以高收率提供结构多样的仲胺。
