Synthesis of N-aryl indole-2-carboxylates via an intramolecular palladium-catalysed annulation of didehydrophenylalanine derivatives

Nitrogen substituted indole-2-carboxylates can be prepared via an intramolecular palladium-catalysed amination reaction of didehydrophenylalanine derivatives using PdCl2(dppf) and KOAc in DMF at 90°C to form the indole nucleus. The specific formation of (Z)-isomers from Horner–Wadsworth–Emmons reaction of phosphonylglycinates and 2-iodobenzaldehydes was crucial to the success of the process. The product N-substituted indole-2-carboxylates were isolated in high yield.