Novel chiral biferrocene ligands for palladium-catalyzed allylic substitution reactions.
Novel chiral biferrocene ligands for palladium-catalyzed allylic substitution reactions.
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用于钯催化烯丙基取代反应的新型手性联二茂铁配体。
DOI：
10.1021/jo016249w
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发表时间：
2002
期刊：
影响因子：
--
通讯作者：
M. Widhalm
中科院分区：
文献类型：
--
作者：
Li Xiao;W. Weissensteiner;K. Mereiter;M. Widhalm
合成了11个新的氨基膦配体，它们都含有手性2，2 "-桥联双二茂铁单元作为双二茂铁氮杂卓亚结构的一部分。研究了这些化合物作为手性助剂在钯催化烯丙基取代反应中的作用。根据适当的配体和环状或非环状底物之间的（空间）配合程度，实现了46- 87%ee的反应。通过X-射线衍射确定的配体之一的二氯化钯配合物的分子结构，并比较其联萘类似物。在固态下，这两种配合物的氮杂卓亚结构采用完全不同的构象，具有局部C（2）（联萘）或局部C（1）（双二茂铁衍生物）对称性。这些结构的变化很好地再现了经验力场计算，也反映在显着不同的行为在不对称催化。
Eleven novel aminophosphine ligands have been synthesized, all of which contain a chiral 2,2' '-bridged biferroceno unit as part of a biferrocenoazepine substructure. The efficiency of these compounds as chiral auxiliaries in palladium-mediated allylic substitution reactions has been investigated. Depending on the degree of (steric) fit between proper ligands and cyclic or noncyclic substrates, reactions with 46-87% ee were achieved. The molecular structure of a palladium dichloride complex of one of the ligands was determined by X-ray diffraction and compared to its binaphthyl analogue. In the solid state, the azepine substructure of these two complexes adopts totally different conformations with either local C(2) (binaphthyl) or local C(1) (biferrocene derivative) symmetry. These structural changes are well-reproduced by empirical force field calculations and are also reflected in significantly different behavior in asymmetric catalysis.