Direct catalytic C-H arylation of imidazo[1,2-a]pyridine with aryl bromides using magnetically recyclable Pd-Fe3O4 nanoparticles

The direct C-H arylation of a heteroarene with aryl bromides has been achieved under the catalysis of magnetic nanoparticles. In the presence of bimetallic Pd-Fe3O4 heterodimer nanocrystals (1 mol % in palladium), the reaction of imidazo[1,2-a]pyridine with various aryl bromides gives the corresponding arylated products with exclusive C3-selectivity. The highly regioselective method is applicable to a wide range of aryl bromides with varying electronic and steric properties. The Pd-Fe3O4 nanocrystals can be recoverable by simple magnetic separation and have been recycled ten times without loss of catalytic activity.