Mengmeng Zhao

Ruthenium-Catalyzed Oxidation of Allyl Alcohols with Intermolecular Hydrogen Transfer: Synthesis of α,β-Unsaturated Carbonyl Compounds

Ruthenium-catalyzed oxidation of multisubstituted allyl alcohols in the presence of benzaldehyde gives enals or enones in good yields. Unlike the commonly reported ruthenium-catalyzed isomerization reaction of allyl alcohols to give saturated ketones, an intermolecular rather than intramolecular hydrogen transfer is involved in this transformation. This reaction offers an efficient, mild, and high-yielding method for the preparation of substituted α,β-unsaturated compounds.

Ru-catalyzed highly enantioselective hydrogenation of α-keto Weinreb amides

Asymmetric hydrogenation of α-keto Weinreb amides has been realized with [Ru((S)-Sunphos)(benzene)Cl]Cl as the catalyst and CeCl3·7H2O as the additive. A series of enantiopure α-hydroxy Weinreb amides (up to 97% ee) have been obtained. Catalytic amount of CeCl3·7H2O is essential for the high reactivity and enantioselectivity and the ratio of CeCl3·7H2O to [Ru((S)-Sunphos)(benzene)Cl]Cl plays an important role in the hydrogenation reaction.

Enantioselective Ruthenium(II)/Xyl-SunPhos/Daipen-Catalyzed Hydrogenation of γ-Ketoamides

A series of γ-hydroxy amides were synthesized with high enantioselectivities (up to 99%) using asymmetric hydrogenation of the corresponding γ-ketoamides in the presence of Ru-Xyl-SunPhos-Daipen catalyst providing key building blocks for a variety of naturally occurring and biologically active compounds.

An Enantioselective Approach to 4-O-Protected-2-cyclopentene-l,4-diol Derivatives via a Rhodium-Catalyzed Redox-Isomerization Reaction

Kinetic resolution of a series of cyclopentene-1,4-diol derivatives has been successfully achieved with enantiomeric excess up to 99.4% and a kf/ks ratio of 55 by a rhodium-catalyzed redox-isomerization reaction in a noncoordinating solvent.

Cationic‐Rhodium‐Catalyzed Kinetic Resolution of Allylic Alcohols through a Redox Isomerization Reaction in a Noncoordinating Solvent

Transition-metal-catalyzed isomerization of allylic alcohols represents an efficient way to generate saturated carbonyl compounds. Various transition metals such as Rh, Ru, Ir, Ni, and Fe have been employed for this transformation. In recent years, the metal-catalyzed asymmetric isomerization of primary and secondary allylic alcohols has attracted much interest. An enantioselective isomerization reaction may proceed in two ways: Type 1 isomerization involves a primary allylic alcohol possessing two different substituents at the 3-position to form an optically active aldehyde with a newly created stereogenic center at the b-position. Type 2 isomerization involves the selective conversion of one enantiomer of the racemic allylic alcohol into a saturated ketone while leaving the other isomer enantiomerically enriched by way of kinetic resolution (Scheme 1). To our knowledge, there are very few reported

Ruthenium-Catalyzed Enantioselective Hydrogenation of Ferrocenyl Ketones: A Synthetic Method for Chiral Ferrocenyl Alcohols

Highly effective asymmetric hydrogenation of various ferrocenyl ketones, including aliphatic ferrocenyl ketones as well as the more challenging aryl ferrocenyl ketones, was realized in the presence of a Ru/diphosphine/diamine bifunctional catalytic system. Excellent enantioselectivities (up to 99.8% ee) and activities (S/C = 5000) could be obtained. These asymmetric hydrogenations provided a convenient and efficient synthetic method for chiral ferrocenyl alcohols, which are key intermediates for a variety of chiral ferrocenyl ligands and resolving reagents.

Ruthenium-Catalyzed Enantioselective Hydrogenation/Lactonization of 2-Acylarylcarboxylates：Direct Access to Chiral 3-Substituted Phthalides

Highly enantioselective tandem hydrogenation/lactonization of various 2‐acylarylcarboxylates including 2‐aroylarylcarboxylates were realized by using [RuCl(benzene)(S)‐SunPhos]Cl as the catalyst under mild reaction conditions. Excellent enantioselectivities (up to 99.6 % ee) and activities (S/C=1000) were obtained. This convenient and practical method enables a direct access to a series of highly optically pure 3‐substituted phthalides that are very important molecules as valuable pharmacological compounds and diversified synthons for medicinal chemistry. Moreover, a gram‐scale reaction was performed to further demonstrate the practicality of this approach.