New Types of Soluble Polymer-Supported Bisphosphine Ligands with a Cyclobutane Backbone for Pd-Catalyzed Enantioselective Allylic Substitution Reactions
作者:Dongbo Zhao、Jie Sun、Kuiling Ding
DOI:10.1002/chem.200400488
日期:2004.12.3
reactions. In particular, the MeO-PEG supported (S,S,S,S)-5 b had a synergistic effect on the enantioselectivity of the reaction compared with its nonsupported precursor (S,S,S,S)-4 c, affording the corresponding allylation products 14 a and 14 b with excellent enantioselectivities (94.6 and 97.2 % ee, respectively). Moreover, the Pd complex of (S,S,S,S)-5 b could easily be recovered and recycled several
通过与TADDOL(-)-8进行分子络合,通过氢键相互作用获得相应的两种对映异构体(-)-和(-)-,可以实现高效的反头消旋香豆素香豆素二聚体7光学拆分。 (+)-7,分别具有70%和75%的收率,且ee大于99%。从对映体纯(-)-7开始,已通过简便的转化以高收率合成了新型的具有环丁烷骨架的C2对称双膦配体(S,S,S,S)-3。评价了这些手性双膦配体在钯催化的不对称烯丙基取代反应中的不对称诱导效率。在实验条件下,可以以优异的收率(高达99%)和对映选择性(高达98.9%ee)获得烯丙基取代产物。通过利用该催化反应的高对映选择性和配体(S,S,S,S)-3的环丁烷骨架上易于衍生的羧酸酯基团,开发出一种新型的类似配体(S,S,S,S) -4以及MeO-PEG负载的可溶性配体(S,S,S,S)-5(PEG =聚乙二醇)也已经合成并用于不对称的烯丙基取代反应中。尤其是,MeO-PEG负载的(S