Hydrodehalogenation of Aryl Chlorides and Aryl Bromides Using a Microwave-Assisted, Copper-Catalyzed Concurrent Tandem Catalysis Methodology

A concurrent tandem catalytic methodology has been developed for the hydrodehalogenation of aryl bromides and aryl chlorides. The first step of the tandem catalytic cycle, halogen exchange, produced yields of 84–97% from aryl bromides using 5 mol % CuI catalyst, 10 mol % N,N′ -dimethylcyclohexane-1,2-diamine ( 1 ), and 2 equiv of NaI in acetonitrile under microwave radiation at 100 °C in 0.5–1.5 h. The same reaction for aryl chlorides appeared to be equilibrium-limited after 1 hour at 200 °C (yields of 5–44%). Both aryl bromides and aryl chlorides were hydrodehalogenated in 12–87% yield using 20 mol % CuI, 1.5 equiv of diamine 1, and 2 equiv of NaI in acetonitrile at 200 °C after 1–2 h. Substrates with oxygen- or nitrogen-containing functional groups had substantially lower yields than hydrocarbon substrates. Deuterium labeling studies suggest that diamine 1 supplies the majority of the hydrogen for the hydrodehalogenation reaction, but solvent can also serve as a source.