(N,N) vs. (N,S) chelation of palladium in asymmetric allylic substitution using bis(thiazoline) ligands:: A theoretical and experimental study

New thiazoline-containing ligands including non-symmetric bis(thiazolines) and oxazoline-thiazolines were synthesized and then compared to C-2-symmetric bis(thiazolines) in the palladium-catalyzed allylic substitution. The experimental results obtained in this study support the hypothesis of a competition between the (N,N) and the (N,S) palladium chelation, when sterically hindered bis(thiazolines) are used as ligands. A quantum chemical study performed on the Pd-complexes derived from three selected ligands, two C-2-symmetric bis(thiazolines) and one oxazoline-thiazoline, also supports this hypothesis. (C) 2008 Elsevier B.V. All rights reserved.