Xiaomin Xie

Ru-catalyzed asymmetric hydrogenation of 3-oxoglutaric acid derivatives via solvent-assisted pinpoint recognition of carbonyls in close chemical propinquity.

Upon comparison of hydrogenation rates of various β-ketocarboxylic acid derivatives, β-ketoamides were found to be hydrogenated slightly faster than β-ketoesters in EtOH in the presence of [RuCl(benzene)(S)-SunPhos]Cl at 70 °C with 20 bar of hydrogen. In THF these differences were so sharpened that β-ketoamides were hydrogenated even faster than in EtOH while the esters were extremely slow. Based on these findings, a series of 3-oxoglutaric acid derived with ester and amide moieties on the two ends were hydrogenated to 3-hydroxyl products with high enantioselectivities.

Diastereo- and enantioselective asymmetric hydrogenation of α-amido-β-keto phosphonates via dynamic kinetic resolution.

Dynamic kinetic resolution of various α-amido-β-keto phosphonates via asymmetric hydrogenation proceeded efficiently to give the corresponding β-hydroxy-α-amido phosphonates in high diastereo- and enantioselectivities (up to 99:1 syn/anti, 99.8% ee). The addition of catalytic amounts of CeCl(3)·7H(2)O is necessary to achieve both good selectivity and catalytic efficiency under mild reaction conditions.

Ru-catalyzed highly chemo- and enantioselective hydrogenation of γ-halo-γ,δ-unsaturated-β-keto esters under neutral conditions

Finely-tuned ruthenium-catalyzed highly chemoselective and enantioselective hydrogenation of γ-halo-γ,δ-unsaturated-β-keto esters at the carbonyl group was achieved under neutral reaction conditions (ee up to 97%). Both olefin and alkenyl halogen moieties, which are labile under hydrogenation conditions, remained untouched during the reaction.

Enantioselective Rhodium-Catalyzed Synthesis of α-Chloromethylene-γ-Butyrolactams from N-Allylic Alkynamides

The first enantioselective cycloisomerization with intramolecular halogen migration of various 1,6-enynes promoted by a cationic Rh-Synphos catalyst is reported. This method provides an efficient route to enantiomerically enriched γ-butyrolactam derivatives, which are important core scaffolds found in numerous natural products and biologically active molecules. Good yields and enantiomeric excesses up to 96% are achieved.

Enantioselective Hydrogenation of β-Ketophosphonates with Chiral Ru(II) Catalysts

Highly effective asymmetric hydrogenation of β-ketophosphonates in the presence of Ru-(S)-SunPhos as catalyst was realized; good to excellent enantioselectivities (up to 99.9% ee) and excellent diastereoselectivities (96:4) were obtained.

Acid-labile δ-ketal-β-hydroxy esters by asymmetric hydrogenation of corresponding δ-ketal-β-keto esters in the presence of CaCO3

A series of acid-labile, optically pure ε-substituted δ-ketal-β-hydroxy esters were obtained by a Ru-SunPhos catalyzed asymmetric hydrogenation of the corresponding ε-substituted δ-ketal-β-keto esters. CaCO(3) played a dual role in the hydrogenation reaction--removing the acid generated during the formation of the catalyst and maintaining the activity of the catalyst.

Ru-Catalyzed Asymmetric Hydrogenation of γ-Heteroatom Substituted β-Keto Esters

A series of enantiomerically pure γ-heteroatom substituted β-hydroxy esters were synthesized with high enantioselectivities (up to 99.1% ee) by hydrogenation of γ-heteroatom substituted β-keto esters in the presence of Ru-(S)-SunPhos catalyst. These asymmetric hydrogenations provide key building blocks for a variety of naturally occurring and biologically active compounds.

Lewis Acid Promoted Carbon−Carbon Double-Bond Formation via Organozinc Reagents and Carbonyl Compounds

Using cheap and readily available AlCl(3) as Lewis acid, functionalized aldehydes react with organozinc reagents to give (E)-alkenes stereoselectively in high yields.

Synthesis of (S)-7-amino-5-azaspiro[2.4]heptane via highly enantioselective hydrogenation of protected ethyl 1-(2-aminoaceto)cyclopropanecarboxylates.

Highly effective asymmetric hydrogenation of protected ethyl 1-(2-aminoaceto)cyclopropane carboxylates in the presence of [RuCl(benzene)(S)-SunPhos]Cl was realized, and high enantioselectivities (up to 98.7% ee) were obtained. This asymmetric hydrogenation provides a key intermediate for the enantioselective synthesis of (S)-7-amino-5-azaspiro[2.4]heptane moiety of quinolone antibacterial agents.

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.