Highly Chemoselective Synthesis of Indole Derivatives.

A facile and efficient synthesis of polysubstituted indoles from α-arylamino-β-hydroxy-2-enamides, α-arylamino-β-oxo-amides, or their tautomeric mixture via electrophilic activation strategy is described. The salient feature of this methodology is the use of either combined Hendrickson reagent and triflic anhydride (Tf O) or triflic acid (TfOH) to control the chemoselectivity in the intramolecular cyclodehydration to provide a predictable approach to these valuable indoles with flexible substituent patterns. Moreover, the mild reaction conditions, simple execution, high chemoselectivity, excellent yields, and wide range of synthetic potential of products make this protocol much attractive for academic research and practical applications.