Catalytic Highly Enantioselective Alkylation of Aldehydes with Deactivated Grignard Reagents and Synthesis of Bioactive Intermediate Secondary Arylpropanols
作者:Yi Liu、Chao-Shan Da、Sheng-Li Yu、Xiao-Gang Yin、Jun-Rui Wang、Xin-Yuan Fan、Wei-Ping Li、Rui Wang
DOI:10.1021/jo101351t
日期:2010.10.15
of the high reactivity of Grignard reagents, a direct, highly enantioselective Grignard reaction with aldehydes has rarely been disclosed. In this report, Grignard reagents were introduced with bis[2-(N,N′-dimethylamino)ethyl] ether (BDMAEE) to effectively deactivate their reactivity; thus, a highly enantioselective alkylation of aldehydes with Grignard reagents resulted from catalysis by (S)-BINOL-Ti(OiPr)2
由于格氏试剂的高反应性,很少公开与醛类直接,高度对映选择性的格氏试剂反应。在该报告中,格氏试剂与双[2-(N,N'-二甲基氨基)乙基]醚(BDMAEE)一起引入,以有效地使其活性失活。因此,由(S)-BINOL-Ti(O i Pr)2催化导致格氏试剂对醛的高度对映选择性烷基化。认为BDMAEE螯合了RMgBr的Schlenk平衡的原位生成的盐MgBr 2和RMgBr与Ti(O i Pr)4的重金属化产生的Mg(O i Pr)Br的螯合作用。镁盐可以积极地促进不希望有的背景反应,生成外消旋体。该螯合作用无疑抑制了Mg盐的催化活性,抑制了不需要的背景反应,并且使得能够被(S)-BINOL-Ti(O i Pr)2催化的高对映选择性加成。因此,与以前的研究相比,没有除去Mg盐的副产物,使用了比RMgBr少的Ti(O i Pr)4,并且在该催化不对称反应中避免了极低的温度。各种烷基格氏试剂中的不对称