Highly efficient asymmetric organocatalytic Friedel–Crafts alkylation of indoles with α,β-unsaturated aldehydes

Abstract

The development of an improved organocatalyst, N-isopropylated bipyrrolidine 2a, for the asymmetric Friedel–Crafts alkylation of indoles with α,β-unsaturated aldehydes has been presented. The new organocatalyst readily facilitates the enantioselective alkylation reaction, providing 3-alkylated indoles in good to high yields (62–89%) with high levels of enantioselectivity (80–93% ee) using only 2 mol% of catalyst loading.