Resting state and kinetic studies on the asymmetric allylic substitutions catalyzed by iridium-phosphoramidite complexes
Resting state and kinetic studies on the asymmetric allylic substitutions catalyzed by iridium-phosphoramidite complexes
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DOI：
10.1021/ja074584h
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发表时间：
2007-09-26
影响因子：
15
通讯作者：
Hartwig, John F.
中科院分区：
文献类型：
--
作者：
Markovic, Dean;Hartwig, John F.
报道了铱催化剂在胺的不对称烯丙基化反应中的静止状态和整个催化循环的动力学数据。静止状态是金属环催化剂与烯丙基胺产物的烯属单元的络合物。含有支链烯丙基胺N -苯基-1-苯基丙-2-烯胺和相关的乙烯络合物的物质已以纯的形式分离。测定了对映体烯丙胺与Ir（I）片段的结合常数。结合亲和力的比率在催化循环中两种对映体胺产物形成速率的比率的实验误差内。催化反应速率对烯丙基碳酸酯、胺和催化剂均为一级反应，对产物均为反一级反应。这种数据的组合，沿着观察到静止状态对1.5当量的烯丙基碳酸酯是稳定的，意味着铱（I）物质与烯丙基碳酸酯的反应是可逆的和吸能的，并且烯丙基中间体与亲核试剂反应形成产物。最后，金属环铱乙烯配合物的简单合成产生用于烯丙基胺化的单组分、高活性和对映选择性催化剂。
The resting state of the iridium catalyst in the asymmetric allylation of amines and kinetic data on the overall catalytic cycle are reported. The resting state is a complex of the metallacyclic catalyst with the olefinic unit of the allylamine product. The species containing the branched allylamine N -phenyl-l-phenylprop-2-enylamine and a related ethylene complex have been isolated in pure form. Binding constants of enantiomeric allylamines to the Ir(I) fragment were measured. The ratio of binding affinities is within experimental error of the ratio of rates for formation of the two enantiomeric amine products in the catalytic cycle. The rates of the catalytic reaction are first-order in allylic carbonate, amine, and catalyst and inverse-first order in product. This combination of data, along with the observation that the resting state is stable toward 1.5 equiv of allylic carbonate, implies that the reaction of the iridium (I) species with the allylic carbonate is reversible and endergonic, and that the allyl intermediate reacts with the nucleophile to form product. Finally, the simple synthesis of the metallacyclic iridium ethylene complex gives rise to a single-component, highly active, and enantioselective catalyst for the allylic amination.