Copper(II) complex dispersed in imidazolium‐based ionic liquid: Recyclable catalyst system for regioselective and chemoselective hydrobromination and hydrochlorination of alkynes

We report a recyclable catalyst system combining Cu(II)O and 4,7‐dimethoxy‐1,10‐phenanthroline in a 1‐ethyl‐3‐methylimidazolium‐based ionic liquid for the hydrohalogenation of alkynes. The reaction efficiently yields alkenyl bromides and chlorides with good functional group tolerance and regioselectivity across a range of functionalized alkynes. Remarkably, the reaction exhibits unprecedented chemoselectivity for alkyne over alkenes in polyenynes and enables late‐stage modifications to rapidly synthesize brominated polyenes. The catalyst system could be recycled for up to six runs without significant reduction of the reaction yield.