Active catalysts for the Suzuki coupling: Palladium complexes of tetrahydropyrimid-2-ylidenes
Active catalysts for the Suzuki coupling: Palladium complexes of tetrahydropyrimid-2-ylidenes
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DOI：
10.1016/j.molcata.2005.08.046
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发表时间：
2006-02
影响因子：
--
通讯作者：
S. Schneider;W. Herrmann;E. Herdtweck
中科院分区：
文献类型：
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作者：
S. Schneider;W. Herrmann;E. Herdtweck
本文介绍了一种合成混合N-杂环卡宾（NHC）膦钯（II）配合物的方法。通过四氢嘧啶鎓盐的去质子化产生的游离卡宾与Pd（PPh 3）2Cl 2反应，得到所需的混合NHC膦钯（II）络合物。在这项工作中，我们结合了混合NHC膦钯配合物在Suzuki偶联反应中的上级活性和更强的σ-供体配体的额外优势。这两种效应的组合导致Suzuki反应中的催化活性比相应的混合咪唑亚基膦络合物所发现的增加。使用这类新的催化剂，吨约100万。在反应时间为14小时后，可以实现。失活的溴代芳烃也可以有效地偶联，使用相当低的量的催化剂（0.005mol%）。甚至芳基氯也可以偶联：仅使用0.01mol%的催化剂，仅在14小时后就可以达到约6000的TON，而没有任何可检测到的催化剂劣化。
An alternative way to synthesize a mixed N-heterocyclic carbenes (NHC) phosphine palladium(II) complex is described in this work. A free carbene, generated by deprotonation of a tetrahydro-pyrimidinium salt, was reacted with Pd(PPh3)2Cl2to yield the desired mixed NHC phosphine palladium(II) complex. In this work, we have combined the superior activity of mixed NHC phosphine palladium complexes in Suzuki-coupling reactions with the additional advantage of a stronger σ-donating ligand. The combination of these two effects results in an increased catalytic activity in Suzuki reactions than found for corresponding mixed imidazole–ylidene phosphine complexes. Using this new class of catalysts, TONs of approximately 1Mio. after a reaction time of 14h can be achieved. Desactivated bromoarenes could also be coupled efficiently, using quite a low amount of catalyst (0.005mol%). Even aryl chlorides can be coupled: TONs of approximately 6000 can be reached after only 14h without any detectable catalyst deterioration using only 0.01mol% of catalyst.