Use of "homeopathic" ligand-free palladium as catalyst for aryl-aryl coupling reactions

被引:185
作者
Alimardanov, A [1 ]
de Vondervoort, LSV [1 ]
de Vries, AHM [1 ]
de Vries, JG [1 ]
机构
[1] DSM, Pharma Chem Adv Synth Catalysis & Dev, NL-6160 MD Geleen, Netherlands
关键词
biaryls; cross-coupling; ligand-free palladium; nanoclusters; Negishi reaction; Suzuki reaction;
D O I
10.1002/adsc.200404210
中图分类号
O69 [应用化学];
学科分类号
081704 ;
摘要
We have previously shown that the use of ligand-free palladium employing Pd(OAC)(2) as catalyst precursor in the Heck reaction of aryl bromides is possible if low catalyst loadings, typically between 0.01-0.1 mol % are used. We have now tested this phenomenon, which we have dubbed "homeopathic" palladium, in biaryl formation using the Suzuki, the Negishi and the Kumada cross-coupling reactions. The Suzuki reaction of aryl bromides, both activated and deactivated, is possible using 0.02-0.05 mol % of Pd(OAC)(2). In this reaction turnover frequencies up to 30,000 have been reached with activated substrates. Even aryl chlorides could be reacted if strongly electron-withdrawing substituents were present. ne Negishi coupling with a variety of arylzinc halides was possible on aryl bromides containing electron-withdrawing substituents. The Kumada reaction only gave low yields of products under "homeopathic' conditions.
引用
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页码:1812 / 1817
页数:6
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