Metal-Free Synthesis of 4-Bromoisoquinolines through Brominative Annulation of 2-Alkynyl Arylimidate Using <i>In Situ</i>-Generated Transient Bromoiodane

Herein, we report the <i>in situ</i>-generated transient bromoiodane-mediated brominative annulation of 2-alkynyl arylimidate for the synthesis of 4-bromoisoquinolines at room temperature. Using a simple hypervalent iodine reagent PIDA as a mild oxidant and potassium bromide as the halogen source, a broad range of valuable 4-bromoisoquinolines can be synthesized in excellent yields. The reaction features readily available chemicals, mild metal-free conditions, and high functional group tolerance, providing an efficient alternative for the construction of halogenated isoquinolines.