Nickel-catalyzed cross-coupling of aryl Grignard reagents with aromatic alkyl ethers: An efficient synthesis of unsymmetrical biaryls
Nickel-catalyzed cross-coupling of aryl Grignard reagents with aromatic alkyl ethers: An efficient synthesis of unsymmetrical biaryls
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DOI：
10.1002/anie.200453765
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发表时间：
2004-01-01
影响因子：
16.6
通讯作者：
Dankwardt, JW
中科院分区：
文献类型：
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作者：
Dankwardt, JW
当在THF中加入5 mol%[NiCl2 (PCy3) 2][7]进行交联反应时，得到了很大的改善（表2，条目1）。此外，还发现在反应混合物中加入10 mol%的PCy3时，联芳基的产率更高（表2，条目2）。溶剂的选择对反应的效率起着重要的作用。确定了非极性溶剂介质是优选的。如表2所示，非极性醚如（EtO） 2CH2、Bu2O、iPr2O和tAmOMe （tAm= CEtMe2）的产率最高。此外，甲苯可以用作溶剂，在某些情况下，它是首选的溶剂系统（表2，条目3）。据推测，当使用非极性介质时，可能会毒害所需催化循环的MgBr （OMe）通过沉淀去除。这可以解释为什么反应不能在更极性的溶剂中如四氢呋喃中达到完全转化。此外，当二甲氧基乙烷或二甘醇作为反应溶剂时，不发生反应。
A major improvement was attained when the crosscoupling reaction was performed with 5 mol%[NiCl2 (PCy3) 2][7] in THF (Table 2, entry 1). In addition, it was found that the yield of biaryl was higher when an additional 10 mol% PCy3 was also added to the reaction mixture (Table 2, entry 2). The choice of solvent played a major role in the efficiency of the reaction. It was determined that nonpolar solvent media was preferred. As illustrated in Table 2, the nonpolar ethers such as (EtO) 2CH2, Bu2O, iPr2O, and tAmOMe (tAm= CEtMe2) afforded the highest yields. In addition, toluene can be utilized as a solvent, and in some cases it was the preferred solvent system (Table 2, entry 3). Presumably, when nonpolar media is used, MgBr (OMe), which may poison the desired catalytic cycle, is removed by precipitation. This may account for the inability of the reaction to reach complete conversion in a more polar solvent such as THF. Furthermore, no reaction transpires when dimethoxyethane or diglyme is used as the reaction solvent.