Since the discovery of the cerium-catalyzed α-hydroxylation of β-dicarbonyl compounds 1 (Scheme 1)^[1] this reaction has been utilized as a racemic method for natural product synthesis.^[2] Despite intensive efforts to establish a catalytic, asymmetric version by application of chiral ligands, today only stoichiometric methods, e.g. with optically active oxaziridines are available.^[3] Hence, objective of the project is the development of new chiral ligands for asymmetric cerium-catalyzed reactions, e.g. based on a C₂-symmetric bis-imidazoline scaffold.^[4]

[1] a) J. Christoffers, T. Werner, S. Unger, W. Frey, Eur. J. Org. Chem. 2003, 425-431; b) J. Christoffers, T. Werner, Synlett 2002, 119-121; c) Review: J. Christoffers, A. Baro, T. Werner, Adv. Synth. Catal. 2004, 346, 143-151.

[2] a) J. Christoffers, T. Werner, W. Frey, A. Baro, Chem. Eur. J. 2004, 10, 1042-1045; b) Y. Wu, C. Du, C. Hu, Y. Li, Z. Xie, J. Org. Chem. 2011, 76, 4075–4081; c) Z.-H. Chen, Y.-Q. Zhang, Z.-M. Chen, Y.-Q. Tu, F.-M. Zhang, Chem. Commun. 2011, 47, 1836–1838; d) Y.-M. Zhao, P. Gu, Y.-Q. Tu, C.-A. Fan, Q. Zhang, Org. Lett. 2008, 10, 1763–1766.

[3] a) J. Lie, G. Chen, Z. Wang, R. Zhang, X. Zhang, K. Ding, Chem. Sci. 2011, 2, 1141–1144; b) S.-H. Cao, M. Shi, Tetrahedron: Asymm. 2010, 21, 2675–2680; c) J.-J. Jiang, J. Huang, D. Wang, M.-X. Zhao, F.-J. Wang, M. Shi, Tetrahedron: Asymm. 2010, 21, 794–799;

[4] M. Schulz, J. Christoffers, Eur. J. Org. Chem. 2013, 7624–7630.