Catalytic enantioselective Michael addition reactions of α-nitroesters to α,β-unsaturated ketones
作者:Erik Keller、Nora Veldman、Anthony L. Spek、Ben L. Feringa
DOI:10.1016/s0957-4166(97)00432-1
日期:1997.10
Enantioselective Michael additions of α-nitroesters 2a-d with α,β-unsaturated ketones were carried out in the presence of a catalytic amount of chiral Al-Li-(R,R′)-2,2′-dihydroxy-1,1′-binaphthyl (‘AlLiBINOL’) complex prepared in situ from LiAlH4 and 2.45 equiv. of (R,R′)-BINOL. The enantioselectivity of the Michael addition proved to be extremely temperature dependent: Michael adduct 4a showed 7% e
在催化量的手性Al-Li-(R,R')-2,2'-dihydroxy-1,1的存在下进行α-硝基酯2a-d与α,β-不饱和酮的对映选择性Michael加成反应-1,1'-联萘(“AlLiBINOL”)复合物制备在原位从的LiAlH 4和2.45当量。(R,R')-BINOL的混合物。迈克尔加成物的对映选择性被证明是极度依赖于温度的:当在室温下进行反应时,迈克尔加成物4a显示7%ee,而相反的4a对映体为72%ee。当在-23℃下进行1,4-加成时发现。溶剂变化表明,四氢呋喃具有最高的选择性(最高80%ee),而对映体的最高对映体选择性在二氯甲烷中(最高25%)。AlLi 3 BINOL 3配合物6的X射线结构分析结合27 Al NMR研究表明,“ AlLiBINOL”是溶液中铝配合物的混合物。