Green electrochemical synthesis of low-molecular-weight multifunctional molecules containing both indole and quinone moieties

Low-molecular weight multifunctional molecules (LWMM) are highly valuable building blocks in organic synthesis because target molecules can be synthesized from them through a simple one-step coupling. On the other hand, the synthesis of these multifunctional molecules themselves is relatively complex due to the large number of functional groups. To demonstrate the capabilities of electrochemical methods in the synthesis of complex molecules, we developed a green and facile electrochemical method for the synthesis of such molecules. This goal has been achieved through the direct oxidation of 4-tert-butylcatechol in the presence of nucleophiles such as 3-(1H-indol-3-yl)-3-oxopropanenitrile. The results show that electrochemically generated 4-tert-butyl-o-benzoquinone participates in a Michael-type reaction with the nucleophile and is converted to the final product after reoxidation. The synthesized compounds contain two moieties, indole and quinone, which are important from a pharmaceutical point of view. In this work, three new low-molecular weight multifunctional molecules with good yields were synthesized in water/ethanol mixture, without the use of toxic reagents and solvents, using a graphite electrode under green chemistry conditions. The synthesized compounds show antibacterial activity against some Gram-positive and Gram-negative bacteria.