Two-Step Continuous Synthesis of Dicarbonyl Indoles via I₂/DMSO-Promoted Oxidative Coupling: A Green and Practical Approach to Valuable Diketones from Aryl Acetaldehydes

A green and practical method for the synthesis of C-3 dicarbonyl indoles from aryl acetaldehydes and indoles was developed under I₂/DMSO conditions, employing an assembled two-step continuous flow system. Moderate to good yields of dicarbonyl indole derivatives have been achieved by consuming a lower dosage of iodine and shorter reaction time without amine catalysts added, which presents major advantages over reactions in a traditional batch. Moreover, this method was also compatible with the synthesis of α-ketoamides and α-ketoesters by adjusting the reaction parameters of a continuous flow system, which indicates its good universality. And a possible mechanism was proposed based on DMSO¹⁸ isotopic labeled experiments.