Stereodivergent Access to Enantioenriched Epoxy Alcohols with Three Stereogenic Centers via Ruthenium-Catalyzed Transfer Hydrogenation

Abstract

The resolution technique of stereodivergent reaction on racemic mixtures (stereodivergent RRM) was employed for the first time in ruthenium complex catalyzed transfer hydrogenation of racemic epoxy ketones, providing a new and very simple method that allows access to enantioenriched epoxy alcohols with three stereogenic centers in a one-step fashion. The protocol features simple reaction conditions, practical operation, ability to scale up, and broad group tolerance.

Escaping from Flatland: Stereoconvergent Synthesis of Three‐Dimensional Scaffolds via Ruthenium(II)‐Catalyzed Noyori–Ikariya Transfer Hydrogenation

“…(Figure 38). [65] These were accessed via Knoevenagel condensation of aryl or alkyl aldehyde and 1,2‐diarylethanone 163 , followed by H 2 O 2 mediated epoxidation to epoxy ketones 164 . Dynamic kinetic resolution involving keto‐enol equilibrium is not possible in this case because of quaternary carbon atom next to the carbonyl function, therefore mixtures of two enantioenriched diastereomers cis ‐ 165 and trans ‐ 165 were obtained which were separated by column chromatography.…”

“…[64] Enantioenriched cis-a nd trans-e poxy alcohols were prepared from the corresponding ketones by Fang et al (Figure 38). [65] These were accessed via Knoevenagelc ondensation of aryl or alkyl aldehydea nd 1,2-diarylethanone 163,f ollowed by H 2 O 2 mediated epoxidation to epoxy ketones 164. Dynamic kineticr esolution involvingk eto-enol equilibrium is not possible in this case because of quaternary carbon atom next to the carbonyl function, therefore mixtures of two enantioenriched diastereomers cis-165 and trans-165 were obtained which were separated by column chromatography.G ood to modest enantioselectivities were obtained fort he reduction of ketones 164 with halo-or alkyl-substituted aromatic rings.D iastereoselective epoxide opening by sodium azide, oxidation to the enantioenrichedk etone 164 and O-benzylation of the alcohol were demonstrated for am odel cis-epoxy alcohol 165 withoutl oss of enantiomeric purity.T he scope of the reaction was expanded to the synthesis of aliphatic ketone-derived secondary alcohols 166 and 167,w here an opposites ense of enantioselectivity was observed for the reduction of carbonyl function.…”

Microwave-assisted oxidation reaction of primary alcohols with sensitive functional groups to aldehydes using ruthenium diphosphorus complexes

“…1 Ruthenium-based complexes represent a versatile group of catalysts that are important in various organic transformations. [2][3][4][5][6] Ru-xantphos complexes, for example, have been successfully employed in hydrogenation and C-C bond coupling reactions. 7,8 As a part of our ongoing study of xanthene transition metal complexes, 8,9 we report here the application of these ligands in the Ru-catalysed oxidation of primary alcohols to aldehydes.…”

Catalytic Asymmetric Transfer Hydrogenation of trans-Chalcone Derivatives Using BINOL-derived Boro-phosphates

“…Many noteworthy achievements have been made in the field of asymmetric transfer hydrogenation (ATH) . To date, a plethora of ATH methodologies have been reported that depend mostly on transition-metal catalysis (e.g., Ir, Ru, Rh, and Fe). Organocatalysts, those catalysts derived from small chiral organic molecules, have become an attractive alternative to metal/chiral ligand-based catalysts for ATH reactions in recent years.…”