Chiral (Cyclopentadienone)iron Complexes for the Catalytic Asymmetric Hydrogenation of Ketones

Abstract

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

Manganese Complexes for (De)Hydrogenation Catalysis: A Comparison to Cobalt and Iron Catalysts

“…Following the report of Morris and co-workers [29] in 2008, there have been al ot of publications on that topic. Based on derivatives of Knçlker's iron complex, the groups of Berkessel (Fe-7), [30] Pignataro/ Piarulli/Gennari (Fe-11) [31,32] as well as Wills (Fe-12) [33] investigated the asymmetric hydrogenation of ketones.Comparable results were obtained using Fe-9. [34] Greatly improved results were achieved by Morris and co-workers using Fe-10.…”

Lutidine‐Based Chiral Pincer Manganese Catalysts for Enantioselective Hydrogenation of Ketones

“…[1] In contrast, chiral catalysts made of earthabundant metals, [2] fore xample,c opper, [3] nickel, [4] iron, [5] or cobalt, [6] have only gained some recent popularity in this area. [1] In contrast, chiral catalysts made of earthabundant metals, [2] fore xample,c opper, [3] nickel, [4] iron, [5] or cobalt, [6] have only gained some recent popularity in this area.…”

“…Thel utidine-based chiral PNN ligands 2 combine the features of Milsteinsp rivileged achiral PNN-type motif [14] and Fiaudsc hiral phospholane segment, [15] and were readily synthesized by the sequence shown in Scheme 1, starting from 3a-e, [16] in good overall yields.T reatment of the ligands 2a-f with Mn(CO) 5 Br furnished the corresponding Mn complexes 1a-f in good yields. 31 PNMR spectra showed these complexes were composed of two isomers in aratio ranging from 1:1t o 4:1, probably caused by the syn and anti orientation of the flexible NH moiety relative to the Mn À Br bond.…”

Use of the Trost Ligand in the Ruthenium‐Catalyzed Asymmetric Hydrogenation of Ketones

“…[b] Determined by GC analysis (see the Supporting Information). [c] Absolute configuration assigned by comparison of the optical rotation sign with literature data …”