Practical Synthesis of Chromeno[2,3‐b]indole Skeleton via an Aldehyde Group Insertion/Aromatization Strategy

The synthesis of chromeno[2,3‐b]indole from simple starting materials remains a demanding process. Herein, 2‐bromoindole undergoes nucleophilic attack from salicylaldehyde, followed by intramolecular insertion of an aldehyde group and aromatization to generate the desired chromeno[2,3‐b]indoles. Moreover, various functional groups were tolerated and a gram‐scale synthesis of the product could be achieved under the optimized condition. One, [2,3‐b]indoles: The synthesis of chromeno[2,3‐b]indoles from simple starting materials is a demanding process. Herein, 2‐bromoindole undergoes nucleophilic attack from salicylaldehyde, followed by intramolecular insertion of an aldehyde group and aromatization to generate the desired chromeno[2,3‐b]indoles. Moreover, various functional groups were tolerated and a gram‐scale synthesis was possible.