Lewis acid-catalyzed [4 + 2] cycloaddition of 3-alkyl-2-vinylindoles with β,γ-unsaturated α-ketoesters

Abstract

A Lewis acid-catalyzed [4 ​+ ​2] cycloaddition of 3-alkyl-2-vinylindoles with β,γ-unsaturated α-ketoesters has been established in the presence of Sc(OTf)3, which afforded a series of indole-containing pyran derivatives in generally good yields (up to 90% yield) with excellent diastereoselectivities (up to ​> 95:5 dr) under mild conditions. This approach not only enriches the chemistry of 3-alkyl-2-vinylindoles, but also has provided an atom-economic method for the synthesis of indole-containing pyran derivatives with potential bioactivity.

Keywords

• Lewis acid catalysis
• [4 + 2] Cycloaddition
• 3-Alkyl-2-vinylindole
• β,γ-Unsaturated α-ketoester
• Indole-containing pyran