Cu(i)(2,5,8,11-tetramethyl-2,5,8,11-tetraazadodecane)+ as a catalyst for Ullmann's reaction

Abstract

Cu(I)L complexes catalyze the Ullmann reaction2-BrC₆H₄CO₂⁻ + H₂O → 2-HOC₆H₄CO₂⁻ + Br⁻ + H⁺however the process is slow and undesirable yields of benzoic acid and diphenoic acid are formed. The optimal ligand, L, for this catalyst should enhance the rate of the process, probably via shifting the redox potential of the Cu(II/I) couple cathodically, inhibit the formation of the diphenoic acid, probably via steric hindrance, and of benzoic acid probably via buffering the solution at pH > 7. The results demonstrate that Cu(I)(2,5,8,11-tetramethyl-2,5,8,11-tetraazadodecane)⁺, i.e. Cu(I) with a ligand which fulfils these requirements, is a very good catalyst for this process with a selectivity of > 97% and high turnover numbers.