Weizheng Fan

Ruthenium-catalyzed enantioselective hydrogenation of aryl-pyridyl ketones.

Various substituted aryl-pyridyl ketones were hydrogenated in the presence of Ru-XylSunPhos-Daipen bifunctional catalytic system with enantiomeric excesses up to 99.5%. Upon introduction of a readily removable ortho-bromo atom to the phenyl ring, enantiomerically enriched 4-chlorophenylpyridylmethanol was obtained by hydrogenation method with 97.3% ee, which provided an important chiral intermediate for some histamine H(1) antagonists.

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.

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 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.

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.

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.

Ru-catalyzed hydrogenation of 3,5-diketo amides: simultaneous control of chemo- and enantioselectivity

By modulating the chelating priorities of the different directing groups in 3,5-diketo amides with the assistance from coordinating solvent, highly chemo- and enantioselective hydrogenation of the C3-carbonyls was achieved in the presence of [RuCl(benzene)(S)-SunPhos]Cl in THF.

RuCl2(PPh3)3-catalyzed chemoselective hydrogenation of β, δ-diketo acid derivatives at the β-carbonyls

Chemoselective reduction of the β-carbonyls in β, δ-diketo acid derivatives was achieved through RuCl2(PPh3)3 catalyzed homogeneous hydrogenation. Tetrahydrofuran (THF) played a key role in the chemoselectivity control. This atom-economical protocol provided β-hydroxy-δ-keto esters and amides as useful intermediates in good to excellent yields.