Applications of Ethynylanilines as Substrates for Construction of Indoles and Indole-Substituted Derivatives

Indole is a core structure in many biologically important natural products such as heteroauxin, tryptophan, hypaphorine, bufotenine and gramine. Further, indole based natural products attracted the attention of many research groups due to their broad range of applications in pharmaceuticals, agrochemicals. Thus, it is essential to cover recent advances in the synthesis of indoles and its derivatives. Historically, indole and its derivatives are synthesized by numerous approaches, which is a vast subject and beyond the scope of this review. Herein, we particularly focused on the last five years progress in synthetic approaches for the construction of indole and its derivatives from the substituted 2-ethynyl anilines using various approaches such as transition-metal catalyzed cyclizations, metal-free, and radical reactions. Therefore, we believe that summarizing these results may be very useful for chemists who are interested in the synthesis of heterocyclic compounds.