Preparation of monodentate phosphinite ligands: their applications in palladium catalyzed Suzuki reactions
Preparation of monodentate phosphinite ligands: their applications in palladium catalyzed Suzuki reactions
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DOI：
10.1016/j.tet.2007.09.070
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发表时间：
2007-12-10
期刊：
影响因子：
2.1
通讯作者：
Hong, Fung-E
中科院分区：
文献类型：
--
作者：
Cheng, Yan-Huei;Weng, Chia-Ming;Hong, Fung-E
以较高的产率合成了2，6-OMe，4-Me，1-OPR2C6H2(5a：R=Ph；5b：R=‘Bu)两种亚膦化合物。两个甲氧基被故意放置在亚膦化合物的2，6位上，从而避免了看似合理的正金属化过程，同时向钯金属配位。5a与PdCl2按2：1和1：1的比例进一步反应，分别得到5a连接的钯配合物{(5a)PdCl(Mu-Cl)}(2)7a和{(5a)PdCl2}8a。从它们的晶体结构可以看出，前者是具有预期分子排列的二聚体络合物，而后者是具有意想不到的、能量不利的顺式构型的单体络合物。相反，从5b与PdCl2的反应中只观察到二聚体的形式。人们认为5b上的大取代基‘Bu阻止了顺式单体络合物的形成。以原位合成的5/Pd(OAc)(2)为催化剂的Suzuki-Miyaura交叉偶联反应具有较好的催化效果。(C)2007爱思唯尔有限公司。保留所有权利。
Two phosphinites 2,6-OMe, 4-Me, 1-OPR2C6H2 (5a: R=Ph; 5b: R='Bu) were prepared in good yields. Two methoxy groups are placed on the 2,6 positions of the phosphinites deliberately thereby to avoid a plausible orthometallation process while coordinating toward palladium metal. Further reaction of 5a with PdCl2 in the ratio of 2:1 and 1: 1 gave 5a ligated palladium complexes {(5a)PdCl(mu-Cl)}(2) 7a and {(5a)PdCl2} 8a, respectively. As revealed from their crystal structures, the former is a dimeric complex with anticipated molecular arrangement; nevertheless, the latter is a monomeric complex with unexpected, energetically unfavorable cis form. By contrast, only dimeric form was observed from the reaction of 5b with PdCl2 It is believed that the bulky substituents, 'Bu, on 5b prevent the formation of a monomeric complex in cis form. Fair to good efficiencies were observed for the Suzuki-Miyaura cross-coupling reactions employed in situ-prepared 5/Pd(OAc)(2) as the catalytic precursor. (c) 2007 Elsevier Ltd. All rights reserved.