Counterintuitive Kinetics in Tsuji-Trost Allylation: Ion-Pair Partitioning and Implications for Asymmetric Catalysis
Counterintuitive Kinetics in Tsuji-Trost Allylation: Ion-Pair Partitioning and Implications for Asymmetric Catalysis
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DOI：
10.1021/ja806278e
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发表时间：
2008-11-05
影响因子：
15
通讯作者：
Purdie, Mark
中科院分区：
文献类型：
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作者：
Evans, Louise A.;Fey, Natalie;Purdie, Mark
单膦配体(L=Ar3P等)钯催化的Tsuji-Trost烯丙化反应动力学与亲电的[L2Pd(烯丙基)](+)催化中间体的翻转限制亲核亲核攻击是一致的。与直觉相反的是，当L被给予更多的电子时，这使得[L2Pd(烯丙基)](+)不那么亲电(高达一个数量级)，观察到更高的周转率。在NaBArF催化下，由于离子对返回的衰减(通过生成[L2Pd(烯丙基)](+)//[bar‘F](-))，在以BINAP(L*)为配体的原型不对称烯丙化反应中，不对称诱导的不对称诱导从28%增加到78%。(M)(n+)([bar‘F](-))(N)共催化在涉及离子反应物或试剂和离子催化循环的其他过渡金属催化过程中具有很大的潜在应用价值。
The kinetics of Pd-catalyzed Tsuji-Trost allylation employing simple phosphine ligands (L = Ar3P, etc.) are consistent with turnover-limiting nucleopile attack of an electrophilic [L2Pd(allyl)](+) catalytic intermediate. Counter-intuitively, when L is made more electron donating, whcih renders [L2Pd(allyl)](+) less electrophilic (by up to an order of magnitude), higher rates of turnover are observed. In the presence of catalytic NaBArF, large rate differentials arise by attenuation of ion-pair return (via generation of [L2Pd(allyl)](+)//[BAr'F](-))a process that also increases the asymmetric induction from 28 to 78% ee in an archetypal assymmetric allylation employing BINAP (L*) as ligand. There is substantial potential for analogous application of (M)(n+) ([BAr'F](-))(n) cocatalysis in other transition metal catalyzed processes involving an ionic reactant or reagent and an ionogenic catalytic cycle.