CBr4-Catalyzed Substituent-Dependent Michael Addition/Paal-Knorr Cyclization of Indole with α,β-Unsaturated Ketones.

We report CBr4 catalyzed Michael addition of indole to α,β-unsaturated ketones for the synthesis of β-indolylketones through halogen bonding catalysis. This reaction is compatible with a diverse range of chalcones, including drug-derived chalcones containing sensitive functional groups such as amides, yielding the addition products in good yields. Additionally, 3-indolyl furanoid motifs have been synthesized through the Michael addition followed by Paal-Knorr cyclization by utilizing various unsymmetrical 1,4-enediones in a one-pot process with good yields.