Hydrodehalogenation of aryl chlorides and aryl bromides using a microwave-assisted, copper-catalyzed concurrent tandem catalysis methodology

Article abstract of DOI:10.1021/om2003706

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. This article not subject to U.S. Copyright. Published 2011 by the American Chemical Society.