Palladium-catalyzed carbon-carbon bond-forming 1,2-ligand migration of organoalanes
Palladium-catalyzed carbon-carbon bond-forming 1,2-ligand migration of organoalanes
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DOI：
10.1021/ja045783t
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发表时间：
2004-12-01
影响因子：
15
通讯作者：
Remorova, AA
中科院分区：
文献类型：
--
作者：
Fillion, E;Carson, RJ;Remorova, AA
描述了一种一锅法，两步法将末端炔转化为乙基甲基取代的苄基季碳中心。(E)-2当在Pd（0）催化剂存在下与芳基卤化物和三氟甲磺酸酯分子内反应时，2，2-二取代-1-烯基二甲基丙二烷已被证明参与1，2-烷基从铝到碳的迁移，伴随着在2-位的芳基化，以提供乙基甲基取代的苄基季碳中心。该方案起始于Cp 2 ZrCl 2催化的末端炔的甲基铝化，随后钯催化的所得（E）-2，2-二取代-1-烯基二甲基丙二烷的分子内芳基化，导致从铝到碳的1，2-甲基转移。在该序列中，总共产生了三个新的C-C单键，并且Me 3Al上的三个烷基中的两个转移到邻近碳的基底上。这种方法被应用到各种基板，并通过氘标记实验，这表明，protodealumination的最终的二烷基铝三氟甲磺酸盐或卤化物中间体由CH 3CN的结果在形成的第四个键的过程中的转换机制进行了研究。
A one-pot, two-step process that transforms terminal alkynes into ethyl methyl-substituted benzylic quaternary carbon centers is described. (E)-2,2-Disubstituted-1-alkenyldimethylalanes have been shown to participate in 1,2-alkyl migration from aluminum to carbon with concomitant arylation at the 2-position to furnish ethyl methyl-substituted benzylic quaternary carbon centers, when reacted intramolecularly with aryl halides and triflates in the presence of a Pd(0) catalyst. The protocol is initiated with Cp2ZrCl2-catalyzed methylalumination of terminal alkynes followed by palladium-catalyzed intramolecular arylation of the resulting (E)-2,2-disubstituted-1-alkenyldimethylalanes, leading to 1,2-methyl shift from aluminum to carbon. In that sequence, a total of three new C−C single bonds are made, and two of the three alkyl groups on Me3Al transferred to the substrate on vicinal carbons. This method was applied to a variety of substrates, and the mechanism was investigated by deuterium-labeling experiments, which revealed that protodealumination of the final dialkylaluminum triflate or halide intermediates by CH3CN results in the formation of the fourth bond in the course of the transformation.