Lewis Acid‐Catalyzed (3+2) Cycloaddition of 2‐Indolylmethanols with β,γ‐Unsaturated α‐Ketoesters.

A Lewis acid‐catalyzed (3+2) cycloaddition of 2‐indolylmethanols with β,γ‐unsaturated α‐ketoesters was established, which afforded a series of cyclopenta[b]indoles in overall high yields (up to 98 %) with excellent diastereoselectivities (up to >95 : 5 dr). This reaction not only represents the first C3‐nucleophilic (3+2) cycloaddition of 2‐indolylmethanols, but also provides a good example for (2+n) cycloaddition of β,γ‐unsaturated α‐ketoesters, which will add new contents to the chemistry of 2‐indolylmethanols. In addition, this approach provides an atom‐economic and useful method for the construction of biologically important cyclopenta[b]indole scaffold. [ABSTRACT FROM AUTHOR]