Copper-catalyzed direct C arylation of heterocycles with aryl bromides: discovery of fluorescent core frameworks.

A window of opportunity: A general copper-catalyzed C-H bond-activation path allows arylation of heterocycles with a wide range of aryl bromides (see scheme). The reaction shows excellent regioselectivity and exhibits good functional group tolerance. The 8-aryl xanthines exhibit fluorescence in a variety of solvents and show promise as reagents for biological imaging.