Highly Enantioselective Copper- and Iron-Catalyzed Intramolecular Cyclopropanation of Indoles

We report the first intra­molecular enantio­selective cyclo­propanation of indoles, which was accomplished in good to high yield (up to 94%) with excellent enantio­selectivity (up to >99.9% ee) by using copper or iron complexes of chiral spiro bis­oxazolines as catalysts. This reaction is a straightforward, efficient method for constructing polycyclic compounds with an all-carbon quaternary stereogenic center at the 3-position of the indole skeleton, a core structure shared by numerous natural products and bioactive compounds.本研究首次报道了吲哚类化合物的分子内对映选择性环丙烷化反应。该反应以手性螺环双噁唑啉（chiral spiro bis-oxazolines）的铜或铁配合物作为催化剂，可获得良好至优异的收率（最高达94%）与极佳的对映选择性（最高>99.9% 对映体过量，enantiomeric excess, ee）。此反应是一种简洁高效的合成方法，能够构建在吲哚骨架3位带有全碳季碳手性中心的多环化合物，而这类核心结构广泛存在于众多天然产物与生物活性化合物中。