Synthesis of Indolin-2-one, Isoindolin-1-one, and Indole Derivatives from Homophthalic Acid

We hereby report the preparation of indolin-2-one and isoindolin-1-one and their derivatives starting from 2-(carboxymethyl)benzoic acid, which was first regiospecifically converted into the isomeric half esters. Transformation of the acid functionalities to the acyl azides followed by Curtius rearrangement gave the regioisomeric isocyanates. Reaction of the isocyanates with aniline produced urethane derivatives. Intramolecular cyclization provided the target compounds.