State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Lanzhou, PR China.
Chemistry. 2010 Feb 1;16(5):1638-45. doi: 10.1002/chem.200902705.
A cooperative catalytic system established by the combination of an iron salt and a chiral Brønsted acid has proven to be effective in the asymmetric Friedel-Crafts alkylation of indoles with beta-aryl alpha'-hydroxy enones. Good to excellent yields and enatioselectivities were observed for a variety of alpha'-hydroxy enones and indoles, particularly for the beta-aryl alpha'-hydroxy enones bearing an electron-withdrawing group at the para position of the phenyl ring (up to 90 % yield and 91 % ee). The proton of the chiral Brønsted acid, the Lewis acid activation site, as well as the inherent basic site for the hydrogen-bonding interaction of the Brønsted acid are responsible for the high catalytic activities and enantioselectivities of the title reaction. A possible reaction mechanism was proposed. The key catalytic species in the catalytic system, the phosphate salt of Fe(III), which was thought to be responsible for the high activity and good enantioselectivity, was then confirmed by ESIMS studies.
一种由铁盐和手性 Brønsted 酸组成的协同催化体系已被证明可有效地用于吲哚与β-芳基α'-羟基烯酮的不对称 Friedel-Crafts 烷基化反应。该反应对各种α'-羟基烯酮和吲哚都具有良好到优秀的产率和对映选择性，特别是对带有吸电子基团的β-芳基α'-羟基烯酮（高达 90%的产率和 91%的对映选择性）。手性 Brønsted 酸的质子、路易斯酸的活化位点以及 Brønsted 酸氢键相互作用的固有碱性位点是该反应具有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。通过 ESIMS 研究进一步证实了催化体系中的关键催化物种，即三价铁的磷酸盐盐，它被认为是高活性和良好对映选择性的原因。
