A Method for the Synthesis of Substituted Quinolines via Electrophilic Cyclization of 1-Azido-2-(2-propynyl)benzene

A new and efficient strategy for the synthesis of substituted quinolines via electrophilic cyclization is developed. The intramolecular cyclization of 1-azido-2-(2-propynyl)benzene 1 proceeds smoothly in the presence of electrophilic reagents (I2, Br2, ICl, NBS, NIS, and HNTf2) in CH3NO2 at room temperature or in the presence of catalytic amounts of AuCl3/AgNTf2 in THF at 100 °C to afford the corresponding quinolines 2 in good to high yields. In the case of the electrophilic reagents, E of 2 is either I, Br, or H, depending on the reagent type, while E of 2 is H in the case of the electrophilic catalyst.