SIAS Chemistry faculty Dr Debajit Maiti, Assistant Professor; Dr Surajit Kayal, Assistant Professor; and Dr Brijesh Kumar Mishra, Associate Professor, have co-authored a research paper titled Catalyst free electro-photochemical C3-functionalization of NH-Indoles, published in the scientific journal Green Chemistry by the Royal Society of Chemistry.
Abstract
Direct C3–H functionalization of unprotected NH-indoles with diazo compounds remains challenging owing to competing N–H reactivity. Herein, a catalyst-, acid-, and base-free electro-photochemical strategy enables selective C3 functionalization under blue-light irradiation and rapid alternating polarity (rAP) electrolysis in methanol. Notably, modulation of the electrochemical waveform and reaction medium provides access to divergent reactivity, highlighting electrochemical control as a means of tuning carbene-transfer selectivity without relying on protecting groups or catalysts. The method accommodates a broad range of indole and diazo ester substrates and provides versatile C3-functionalized indoles for further synthetic elaboration. Mechanistic and DFT studies support a reaction pathway governed by the interplay of visible-light excitation, electrochemical waveform, and solvent environment, providing insight into the origin of the divergent reactivity. Green-metrics analysis further demonstrates reduced material consumption and waste generation relative to representative catalytic C3-functionalization methods. Collectively, these findings establish electrochemical waveform engineering as a complementary strategy for controlling site selectivity in catalyst-free carbene-transfer chemistry, while providing a practical and resource-efficient approach to the direct C3-functionalization of unprotected NH-indoles.
