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.