Highly efficient aqueous phase reduction of nitroarenes catalyzed by phosphine-decorated polymer immobilized ionic liquid stabilized PdNPs
Highly efficient aqueous phase reduction of nitroarenes catalyzed by phosphine-decorated polymer immobilized ionic liquid stabilized PdNPs
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DOI：
10.1039/c7cy02557b
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发表时间：
2018-03-07
影响因子：
5
通讯作者：
Lovelock, K.
中科院分区：
文献类型：
--
作者：
Doherty, S.;Knight, J. G.;Lovelock, K.
以弱交联膦修饰聚合物固定的离子液体(PIIL)及其聚乙二醇化离子液体(PEGPIIL)稳定的钯纳米粒子是一种高效的催化剂，可以在温和的条件下以低催化剂的负载量用于多种硝基和杂芳烃的水相加氢和基于硼氢化钠的还原。引入广泛的交联剂与三(4-乙烯基苯基)膦分离膦基杂原子，限制表面Pd中心点P相互作用的数目，对催化剂的性能没有明显影响。对比试验表明，负载在聚乙二醇化聚合物上的PdNPs是一种催化硝基芳烃水相还原的高效催化剂，其催化加氢反应的量为36000吨(TOF=2580h-1)，转移加氢的量为274000吨(TOF=17125h-1)。即使这些反应是在扩散控制下进行的，因为底物的溶解性很差，但这些值是报道过的由纳米颗粒体系催化的室温水相还原硝基芳烃的最高值。在固定床反应器中连续流动还原250min，没有催化剂失活迹象，相应的时空产率为0.738克L-1分(-1)，比间歇生产的0.384克L-1分(-1)有了显著的改善。该体系还催化了Suzuki-Miyaura交叉偶联-硝基芳烃的串联还原序列，从而在操作简单的单锅程序中获得了高产率的联芳胺。这是一种通用性很强的协议，它将使芳香硝基片段能够作为硝基取代的芳基或杂芳基卤化物引入，因此将有助于快速多样化，以合成广泛的胺。
Palladium nanoparticles stabilized by lightly cross-linked phosphine-decorated polymer immobilized ionic liquids (PIIL) and their PEGylated counterparts (PEGPIIL) are highly effective catalysts for the aqueous phase hydrogenation and sodium borohydride-based reduction of a wide range of nitroaromatic and heteroaromatic compounds under mild conditions with low catalyst loadings. Introduction of extensive cross-linking with tris(4-vinylphenyl)phosphine to isolate the phosphine-based heteroatom and limit the number of surface Pd center dot center dot center dot P interactions did not have a significant influence on catalyst performance. Comparative testing revealed PdNPs immobilized on lightly cross-linked phsophine-decoarted PEGylated polymer to be a highly efficient catalyst for the aqueous phase reduction of nitroarenes with a TON of 36000 (TOF = 2580 h(-1)) for hydrogenation and a TON of 274 000 (TOF = 17 125 h(-1)) for transfer hydrogenation. Even though these reactions occur under diffusion control due the poor solubility of the substrate these values are the highest to be reported for the room temperature aqueous phase reduction of nitroarenes catalyzed by a nanoparticle-based system. A continuous flow reduction of nitrobenzene in a packed bed reactor operated over a period of 250 min with no sign of catalyst deactivation and the corresponding space-time-yield of 0.738 g L-1 min(-1) is a marked improvement on that of 0.384 g L-1 min(-1) obtained in batch. The same system also catalyzes a tandem Suzuki-Miyaura cross coupling-nitroarene reduction sequence to afford high yields of biaryl amine in an operationally straightforward single-pot procedure. This is a highly versatile protocol which will enable the aromatic nitro fragment to be introduced as a nitro-substituted aryl or heteroaryl halide and as such will lend itself to rapid diversification for the synthesis of a wide range of amines.