[1,3]-Carboxylic Ester Transfer Reactions: Synthesis of Structurally Challenging Bisindolylmethyl Chromone Hybrids

Herein, we report the first example of a [1,3]-carboxylic ester transfer reaction of chromone-based α-keto esters with indoles for the efficient synthesis of densely functionalized bisindolylmethyl chromone hybrids. These structurally challenging products, including two bisindolylmethane and chromone substructures, which significantly enriched their molecular diversity and complexity, were smoothly afforded in moderate yields under Sc(OTf)3 catalysis. The possible reaction mechanism was proposed according to the single-crystal X-ray analysis of the products and control experiments. Furthermore, biological tests reveal that some of these bisindolylmethyl chromone hybrids displayed good bioactivity as antitumor agents against K562, HeLa, and AGS cancer cells.