Synthetic Organic Chemistry Laboratory, Advanced Science Institute, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
Chem Commun (Camb). 2009 Oct 21(39):5787-98. doi: 10.1039/b911015a. Epub 2009 Aug 17.
Chiral cationic Pd aqua complexes can function as acid-base catalysts, effectively activating active methylene and methine compounds to give chiral Pd enolates. It is noteworthy that such enolate formation occurs with concomitant formation of a strong protic acid. Although the reactivity of the Pd enolate itself is not sufficient for reactions with carbon-based electrophiles, its cooperative action with the protic acid to activate the electrophiles allows the desired C-C bond-forming reactions to proceed smoothly in a highly enantioselective manner. Based on this mechanistic feature, reactions with acetals have been developed; these are difficult to achieve using conventional basic enolate chemistry.
手性阳离子钯水配合物可用作酸碱催化剂，有效地激活活泼亚甲基和亚甲基化合物，得到手性钯烯醇化物。值得注意的是，这种烯醇化物的形成伴随着强酸的生成。虽然钯烯醇化物本身的反应性不足以与碳基亲电试剂发生反应，但它与质子酸的协同作用可以激活亲电试剂，从而使所需的 C-C 键形成反应以高度对映选择性的方式顺利进行。基于这一机理特征，已经开发出与缩醛的反应；这些反应用传统的碱性烯醇化物化学方法难以实现。
