N-Heterocyclic Carbene-Palladium and -Copper Complexes in Cross-Coupling Reactions

Chapter 1 gives the reader a background on cross-coupling reactions, in particular palladium mediated couplings. Furthermore the importance of ligands, including phosphines and N-heterocyclic carbenes (NHC), in such cross-coupling reactions is explored. Chapter 2 provides a background to the reductive lithiation of phosphines, followed by an account of our investigation of BINAP functionalisation by means of reductive elimination. The reaction was examined by experimental means and through the use of density functional theory to predict P NMR chemical shifts. Chapter 3 provides background on the Heck reaction and selected developments over the years, with particular reference to the use of aryl chlorides in the reaction. A brief discussion of NHC based palladium complex sets the scene for our investigation of a new class of (NHC)-Pd catalysts developed by the Navarro group. Complexes of type (NHC)PdCl2(TEA) (TEA = triethylamine) have been tested for their activity in the Heck reaction, focusing on the scope of the reaction with electron-deficient aryl chlorides and electron-rich aryl bromides. Chapter 4 gives an account of the discovery and developments of the Sonogashira reaction. Particular attention is paid to non-classical systems such as palladium-only and copper-only protocols. Herein our investigation into the use of collaborative (NHC)-Pd and (NHC)-Cu in Sonogashira reactions is presented. Notable features of this system are the low catalyst loadings and the synthetically convenient conditions in which the reaction can be carried namely non-anhydrous solvents and in air. Publications: (1) Gallop, C. W. D.; Bobin, M.; Hourani, P.; Dwyer, J.; Roe, S. M.; Viseux, E. M. E. J. Org. Chem. 2013, 6522–6528. (2) Gallop, C. W. D.; Zinser, C.; Guest, D.; Navarro, O. Synlett 2014, 2225–2228. (3) Gallop, C. W. D.; Chen, M.-T.; Navarro, O. Org. Lett 2014, 3724–3727.