Chiral N-Heterocyclic Carbene. Copper(I)-Catalyzed Asymmetric Allylic Arylation of Aliphatic Allylic Bromides : Steric and Electronic Effects on γ-Selectivity
Chiral N-Heterocyclic Carbene. Copper(I)-Catalyzed Asymmetric Allylic Arylation of Aliphatic Allylic Bromides : Steric and Electronic Effects on γ-Selectivity
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手性 N-杂环卡宾。铜 (I) 催化的脂肪族烯丙基溴化物的不对称烯丙基化：对 γ 选择性的空间和电子效应
DOI：
10.1021/jo102386s
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
K
中科院分区：
文献类型：
--
作者：
Selim;K. B.; Nakanishi;H.; Matsumoto;Y.; Yamamoto;Y.; Yamada;K.; Tomioka;K
通过对手性N-杂环卡宾配体的电子和空间结构进行调节，提高了铜催化的脂肪族烯丙基溴与几种芳基格氏试剂的不对称烯丙基芳基化反应的γ-选择性.当Grignard试剂的芳基或卡宾配体的N-取代基上的芳基是缺电子的或当卡宾配体或烯丙基溴是庞大的时，实现高的γ-选择性。结果表明，初始形成的α-烯丙基铜中间体的缺电子和空间位阻促进了还原消除反应，生成γ-产物作为主要异构体。
Chiral N-heterocyclic carbene ligands were electronically and sterically tuned to improve γ-selectivity in copper(I)-catalyzed asymmetric allylic arylation of aliphatic allylic bromides with several aryl Grignard reagents. High γ-selectivity was realized when either the aryl group of the Grignard reagent or the aryl group on the N-substituent of the carbene ligand was electron-deficient or when either the carbene ligand or allylic bromide was bulky. The results indicated that electron deficiency and steric hindrance of the initially formed σ-allyl copper intermediate enhance the rate of the reductive elimination to give γ-products as major isomers.