A family of ferrocene-based chiral PNP ligands is reported. These tridentate ligands were successfully applied in Mncatalyzed asymmetric hydrogenation of ketones, giving high enantioselectivities (92%∼99% ee for aryl alkyl ketones) as well as high efficiencies (TON up to 2000). In addition, dialkyl ketones could also be hydrogenated smoothly. Manganese intermediates that might be involved in the catalytic cycle were analyzed. DFT calculation was carried out to help understand the chiral induction model. The Mn/PNP catalyst could discriminate two groups with different steric properties by deformation of the phosphine moiety in the flexible 5-membered ring.
Asymmetric catalysis | Hydrogenation | Cyclic enone | Rhodium | Citral reduction The enantioselective hydrogenation of endocyclic enones has been a historical problem for homogeneous catalysis. We herein report an efficient method to reduce endocyclic enones with molecular hydrogen. Catalyzed by a rhodium/Zhaophos complex, a variety of enones with five-, six-or seven-member ring were hydrogenated with high enantioselectivity (92%-99% ee). Excellent chemo-and enantioselectivity demonstrated this method was successfully applied in the enantioselective hydrogenation of citral to produce enantio-enriched citronellal.
We
herein report a convenient method to convert olefins to organic
iodides and amines using an Ir/ZhaoPhos catalyst, molecular hydrogen,
and an electrophilic iodine(I) reagent. High yields and regioselectivities
were obtained under mild conditions. In addition, basic workup with
potassium carbonate leads to C–N products. Control experiments
and DFT calculations tentatively excluded the pathway involving the in situ formation of HI. Instead, a catalytic cycle involving
the hydrogenation of the haliranium ion intermediate was proposed.
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