Immobilization of copper in organic-inorganic hybrid materials: a highly efficient and reusable catalyst for the Ullmann diaryl etherification

The immobilization of copper in organic-inorganic hybrid materials catalyzing the Ullmann reaction has been described. Phenols reacted with aryl iodides, aryl bromides and aryl chlorides smoothly in the presence of a 3-(2-aminoethylamino)propyl functionalized silica gel immobilized copper catalyst. The protocol involved the use of DMSO as the solvent, and potassium fluoride as the base. The reactions generated the corresponding cross-coupling products in good to excellent yields. Furthermore, the silica-supported copper could be recovered and recycled by a simple filtration of the reaction solution and used for 10 consecutive trials without loss of its reactivity. (c) 2006 Elsevier Ltd. All rights reserved.