A Green Synthetic Approach to Construct C2‐Quaternary Indolin‐3‐Ones at Room Temperature via Regioselective Oxidative Dearomatization of Indoles

Abstract A new synthetic strategy for the construction of C2‐quaternary indole for the formation of Indolin‐3‐ones has been explored via indium(III) trifluoromethansulphonate catalyst at room temperature with TBHP as a green oxidant in water. This approach for the oxidative dearomatization process allows for the production of the natural product Halichrome A and a broad range of C2‐arylated Indolin‐3‐ones under a milder condition in very good yields. The oxidative self‐dimerization and self‐trimerization of various indole derivatives have also been achieved under the same conditions.