Unlike the widely studied linear diaryliodoniums as electrophilic arylating reagents, cyclic diaryliodoniums have the potential to initiate dual arylations with atom and step economy. In our current work, cascade reactions of cyclic diaryliodoniums and two equivalent alkynes have been successfully achieved under mild conditions, catalyzed by CuI/PdCl₂(PPh₃)₂. The transformation could also be realized in a stepwise way with two different alkynes or with one alkyne and one alkene. The reaction enables a rapid access to a variety of complex fluorenes containing conjugate enyne and diene fragments.

Although cyclic diaryliodonium species have the potential to act as valuable synthons for cascade transformations, they still remain largely unexplored. The regioselectivity associated with unsymmetrical cyclic diaryliodonium species has previously been known to pose a challenge. A regioselective relayed alkynylation and olefination of unsymmetrical cyclic diaryliodonium species has been achieved by installation of a directing amido group. These relayed transformations were delayed until an oxazole ring had formed, delivering a series of unique fluorescent benzoxazoles. Moreover, some of these synthetic benzoxazoles showed apparent inhibitory activity against malignant cancer cells. Further confocal visualization revealed that benzoxazoles targeted cell nuclei. These findings might provide a novel structural scaffold to develop desirable anticancer agents.