Three chiral (cyclopentadienone)iron complexes derived from (R)-BINOL (CK1-3) were synthesized and their structures unambiguously confirmed by X-ray analysis (CK3). Under suitable conditions for the in situ conversion into the corresponding (hydroxycyclopentadienyl)iron hydrides (Me3NO, H2), the new chiral complexes were tested in the catalytic asymmetric hydrogenation of ketones, showing moderate to good enantioselectivity. In particular, the complex bearing methoxy substituents at the 3,3-positions of the binaphthyl moiety (CK2) proved remarkably more enantioselective than the unsubstituted one (CK1) and reached the highest level of enantioselectivity (up to 77% ee) ever obtained with chiral (cyclopentadienone)iron complexes. Reducto! Chiral (cyclopentadienone)iron complexes were synthesized and tested, after in situ activation, in the catalytic asymmetric hydrogenation of ketones leading to the highest enantiomeric excesses ever obtained with this type of catalyst

Herein, we report the synthesis of [bis(hexamethylene)cyclopentadienone]iron tricarbonyl (1 b) by the reaction of cyclooctyne with Fe(CO)5 and the investigation of its catalytic properties in C=O bond reduction. As a result of the peculiar reactivity of cyclooctyne, 1 b was formed in good yield (56 %) by intermolecular cyclative carbonylation/complexation with Fe(CO)5. Compound 1 b was characterized fully and its crystal structure was determined by using XRD. Catalytic tests revealed that, upon in situ activation with Me3NO, 1 b promotes the hydrogenation of ketones, aldehydes, and activated esters as well as the transfer hydrogenation of ketones and shows a higher activity than the classical “Knölker complex” (1 a). Studies on the hydrogenation kinetics in the presence of 1 a and 1 b (respectively) suggest that this difference in activity is probably caused by the better stability of the 1 b‐derived complex than that of the in situ generated Knölker–Casey catalyst.

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, OSO2R) 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.

Here we report the catalytic transfer hydrogenation (CTH) of non-activated imines promoted by a Fe-catalyst in the absence of Lewis acid co-catalysts. Use of the (cyclopentadienone) iron complex 1, which is much more active than the classical 'Knö lker complex' 2, allowed to reduce a number of N-aryl and N-alkyl imines in very good yields using iPrOH as hydrogen source. The reaction proceeds with relatively low catalyst loading (0.5-2 mol%) and, remarkably, its scope includes also ketimines, whose reduction with a Fe-complex as the only catalyst has little precedents. Based on this methodology, we developed a one-pot CTH protocol for the reductive amination of aldehydes/ ketones, which provides access to secondary amines in high yield without the need to isolate imine intermediates.