Efficient and versatile sol-gel immobilized copper catalyst for ullmann arylation of phenols

Abstract

A new hybrid silica with urea-based bipyridyl bridging units has been synthesized by a solgel process. The copper-complexed hybrid silica is an efficient heterogeneous catalyst for the Ullmann coupling of aryl halides with phenols. It is easily withdrawn and recovered from the reaction media by filtration. It is also a versatile catalyst for subsequent reactions with several substrates yielding products with the same efficiency even after ten reuses and with minimal leaching. This is the first example of the use of a copper-complexed bridged silsesquioxane for the preparation of a recoverable catalyst in modern Ullmann chemistry. This may represent a promising route to the reduction of waste while maintaining economic viability. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.