[5]Ferrocenophanene-Phosphane Ligands for Enantioselective Rh-Catalyzed Conjugate Additions

Ferrocenophanene–phosphane ligands with bridged cyclopentadienyl rings have been synthesized and characterized by spectroscopic methods. Rhodium complexes of these ligands can catalyze the Michael addition of phenylboronic acid to cyclic enones and lactones with good yields and an interesting level of stereoselectivity [up to a 95:5 enantiomeric ratio (er)]. In comparison, a ligand without a bridge between the cyclopentadienyl rings affords a product with a lower enantioselectivity (er = 78:22). Planar‐chiral ferrocenophanene–phosphane ligands can complex with rhodium atoms to efficiently catalyze the conjugate addition of phenylboronic acid to cyclic enones and lactones.