Asymmetric Synthesis via chiral pi-Allyl- palladium complexes

我们发现了钯催化的手性胺、亚胺和腙的不对称烯丙化反应的第一个例子，这些烯丙化反应来源于易于获得的光学活性α -氨基酸烯丙酯，如(S)-脯氨酸和(S)-缬氨酸衍生物。由(S)-脯氨酸衍生物衍生的具有膦基的手性胺或腙在钯催化的烯化反应中具有很高的对映选择性，其中膦基作为分子内手性配体，并且烯化试剂的阴离子对应物对不对称诱导具有很强的立体电子效应。在钯催化反应条件下，携带烯丙化部分的手性胺发生分子内不对称烯丙化反应，生成具有光学活性的环化合物。这种不对称碳-碳键形成的新方法被应用于吲哚类生物碱和单萜烯等光学活性天然产物的合成。

We have found the first example of the palladium-catalyzed asymmetric allylations of chiral enamines, imines, and hydrazones derived from readily obtainable optically active alpha-amino acid allyl esters such as (S)-proline and (S)-valine derivatives.Chiral enamines or hydrazones having phosphine groups, which was derived from (S)-proline derivatives, represented high enantioselectivity in the palladium-catalyzed allylations, in which the phosphine groups served as intramolecular chiral ligands and the great stereoelectronic effects of the anionic counterparts of the allylating reagents on the asymmetric induction were observed.Chiral enamines bearing allylating parts underwent intramolecular asymmetric allylations under palladium-catalyzed reaction conditions, affording optically active cyclic compounds. this novel method for asymmetric carbon-carbon bond formations was applied to the synthesis of optically active natural products such as indole alkaloids and monoterpenes.