Cu(I)-USY as a Ligand-Free and Recyclable Catalytic System for the Ullmann-Type Diaryl Ether Synthesis.

The catalytic potential of copper(I)-exchanged zeolites was evaluated in the Ullmann-type synthesis of diaryl ethers. Among four investigated zeolites (i.e., USY, MOR, β, and ZSM5), Cu(I)-USY was the best catalyst and proved efficient under ligand-free conditions in toluene at 120 °C. Cu(I)-USY was also easy to recover and was recyclable up to five times without significant loss of activity.