Synthesis of (R)‐BINOL‐Derived (Cyclopentadienone)iron Complexes and Their Application in the Catalytic Asymmetric Hydrogenation of Ketones

A family of chiral (cyclopentadienone)iron complexes, featuring an ( R )‐BINOL‐derived backbone, and their application in the asymmetric hydrogenation of ketones are described. The complexes differ from each other in the substituents at the 3,3′‐positions of the binaphthyl residue (H, OH, OR, OCOR, OSO 2 R) or at the 2,5‐positions of the cyclopentadienone ring [trimethylsilyl (TMS) or Ph]. Remarkably, eight precatalysts with different 3,3′‐binaphthyl substitution [( R )‐ 1c – 1j ] were synthesized from a common parent complex [( R )‐ 1b ] through direct functional group interconversion reactions of the complexes. The 3,3′‐(bis)methoxy‐substituted precatalyst ( R )‐ 1b gave the best catalytic performance, and its application scope was assessed in the hydrogenation of several ketones. The observed ee values (up to 77 %) are much higher than those previously reported for other chiral (cyclopentadienone)iron complexes.