Chiral Brønsted Acid Directed Iron-Catalyzed Enantioselective Friedel-Crafts Alkylation of Indoles with β-Aryl α′-Hydroxy Enones
作者:Lei Yang、Qiming Zhu、Shengmei Guo、Bo Qian、Chungu Xia、Hanmin Huang
DOI:10.1002/chem.200902705
日期:2010.2.1
of an iron salt and a chiral Brønsted acid has proven to be effective in the asymmetric Friedel–Crafts alkylation of indoles with β‐aryl α′‐hydroxy enones. Good to excellent yields and enatioselectivities were observed for a variety of α′‐hydroxy enones and indoles, particularly for the β‐aryl α′‐hydroxy enones bearing an electron‐withdrawing group at the para position of the phenyl ring (up to 90 %
铁盐和手性布朗斯台德酸的组合建立的协同催化体系已被证明可有效地使吲哚与β-芳基α'-羟基烯酮的不对称Friedel-Crafts烷基化反应。观察到各种α'-羟基烯酮和吲哚的收率和对映选择性均良好至极好,特别是对于在苯环对位带有吸电子基团的β-芳基α'-羟基烯酮(高达90%产量和91% ee)。手性布朗斯台德酸的质子,路易斯酸的活化位点以及布朗斯台德酸的氢键相互作用的固有碱性位点是标题反应的高催化活性和对映选择性的原因。提出了一种可能的反应机理。然后通过ESIMS研究确认了催化体系中的关键催化物质Fe III的磷酸盐,该盐被认为具有高活性和良好的对映选择性。