To enhance productivity, we utilized flow electrolysis. Bocprotected substrates were chosen for flow synthesis as they degrade slowly due to the electrogenerated acid (EGA). The use of a divided flow electrolysis cell and Bu4NB(C6F5)4/CH2Cl2 electrolyte significantly enhanced yields for 2ac and 2db compared to the batch system. This yield enhancement was attributed to the design of the flow cell, which sequentially removes the EGA from the reaction system (Figure ). Subsequently, this flow system was employed in the synthesis of a pharmaceutically relevant compound (Figure ). We successfully synthesized 2j, a synthetic intermediate of pitavastatin, through the ring expansion of indole-derivative (1j). It is noteworthy that our reaction is compatible with cyclopropane substituents despite the formation of a radical cation intermediate. This compatibility may be due to the delocalization of the radical generated within the π-system, preventing cleavage of the C-C bond in the neighboring cyclopropane ring.