Combinatorial transition-metal catalysis: Mixing monodentate ligands to control enantio-, diastereo-, and regioselectivity

This review focuses on a new approach to combinatorial homogeneous transition-metal catalysis which goes beyond the traditional parallel preparation of modular ligands. It is based on the use of mixtures of monodentate ligands La and Lb, which upon exposure to a transition metal (M) form not only the two homocombinations [ML aLa] and [MLbLb], but also the heterocombination [MLaLb]. If the latter is more reactive and selective than the homocombinations, an improved catalyst system is formed without the need to synthesize new ligands. Thus, the control of enantio,- diastereo-, and regioselectivity is possible. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.