Efficient Asymmetric Synthesis of Planar‐Chiral Bisferrocenes

SAMP auxiliary‐derived monosubstituted diferrocenyl ketones have been subjected to ortho ‐metalation/functionalization reactions to prepare chiral disubstituted bisferrocenes. The reactions proceeded in low to moderate yields (20–54 %) and excellent stereoselectivities (97 – ≥ 99 % ee , ≥ 96 % de ), however low regio‐selectivities were obtained in several cases. Monosubstituted bisferrocenes, containing only a planar‐chiral element, were excellent substrates in the same ortho ‐metalation/functionalization reaction affording disubstituted bisferrocenes in moderate to excellent yields (39–99 %) and generally excellent levels of asymmetric induction (≥96 % de ) with complete regiocontrol. The synthesis of related methylene‐bridged mono‐ and di‐substituted diferrocenyl ligands containing N ‐, O ‐, P ‐ and/or S ‐donor atoms is also described.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)