Palladium-catalyzed asymmetric allylic alkylation of ketone enolates
Palladium-catalyzed asymmetric allylic alkylation of ketone enolates
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DOI：
10.1002/chem.200400666
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发表时间：
2005-01-01
影响因子：
4.3
通讯作者：
Schroeder, GM
中科院分区：
文献类型：
--
作者：
Trost, BM;Schroeder, GM
钯催化不稳定酮烯醇酸盐的不对称烯丙基烷基化反应生成四元中心，具有良好的产率和对映体选择性。优化的反应条件为：以2个当量的LDA为碱，1个当量的三甲基氯化锡为Lewis酸，1，2-二甲氧基乙烷为溶剂，催化量的对烯丙基氯化钯二聚体3与环己二胺衍生的手性配体4形成的手性钯配合物。线性取代、无环1，3-二烷基取代和未取代的烯丙基碳酸酯具有亲电作用。多种α-四酮、环己酮和环戊酮可用作亲核试剂。生成的绝对构型与目前的立体因素控制立体面分化的模型一致。用这种方法得到的季胺取代产物是用于进一步精制的多用途底物。
Palladium-catalyzed asymmetric allylic alkylation of nonstabilized ketone enolates to generate quaternary centers has been achieved in excellent yield and enantioselectivity. Optimized conditions consist of performing the reaction in the presence of two equivalents of LDA as base, one equivalent of trimethytin chloride as a Lewis acid, 1,2-dimethoxyethane as the solvent, and a catalytic amount of a chiral palladium complex formed from pi-allyl palladium chloride dimer 3 and cyclohexyldiamine derived chiral ligand 4. Linearly substituted, acyclic 1,3-dialkyl substituted, and unsubstituted allylic carbonates function well as electrophiles. A variety of alpha-tetralones, cyclohexanones, and cyclopentanones can be employed as nucleophiles. The absolute configuration generated is consistent with the current model in which steric factors control stereofacial differentiation. The quaternary substituted products available by this method are versatile substrates for further elaboration.