Synthesis of 3-substituted Indoles through Yonemitsu Reaction with Copper Benzene-1,3,5-tricarboxylate acid Catalyst

3-substituted indole derivatives as a key intermediate for the synthesis of complex indole alkaloids have been synthesized by Yonemitsu condensation reaction between indole, dimedone, and benzaldehyde. This reaction was carried out using copper benzene-1,3,5-trioxylate acid catalyst for the first time. In addition to its acidic properties, the aforementioned catalyst has a 3D network, and the existence of these holes can help to advance the reaction. This reaction proceeds smoothly and has achieved good yields (80-90%) by using water as a green solvent at 60°C. The investigations show that the electron-withdrawing groups on the aldehyde compound perform the reaction at a higher speed, which is completely consistent with the presented mechanism and the presence of the carbocation. This modified reaction has numerous advantages, including high efficiency, short reaction time, low reaction temperature, and the use of water as a green solvent.