Synergistic Cooperative Effect of Sodium borohydride‐Iodine Towards Cascade C−N and C−S/Se Bond Formation: One‐pot Regioselective Synthesis of 3‐Sulfenyl/selenyl Indoles and Mechanistic Insight

In this work, a new strategy to synthesize 3‐sulfenyl/selenyl indole is reported wherein LC−MS reveals a novel insight into synergistic cooperative effect of NaBH4‐I2 which allows cascade C−N and C−S/C−Se bond formations via reduction‐nucleophilic cyclization‐chalcogenylation, three steps in one‐pot, towards regioselective synthesis of diverse 3‐chalcogenyl indoles including 5‐bromo‐3‐[(3,4,5‐trimethoxyphenyl)thio]‐1H‐indole, a known lead anticancer compound, directly from 2‐amino‐phenacylchlorides and thiophenols or disulfides/diselenides in aqueous dioxane under transition‐metal‐free condition.