Synthesis, structure, and characterization of chiral Ru(II) aminophosphine phosphinite complexes and their application in asymmetric hydrogenation of α-functionalized ketones. X-ray crystal structure of Ru{(S)-Ph,Ph-ProNOP}(2-methylallyl)2

Frédéric Hapiot, Francine Agbossou, Catherine Méliet, André Mortreux, Georgina M. Rosair, Alan J. Welch

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Abstract

Reactions of the ruthenium(II) precursors [RuCl2(C6H6)]2 and [RuI2(p-cymene)]2 with the aminophosphine phosphinite ligands (AMPP) (S)-Cy,Cy-ProNOP and (S)-Ph,Ph-ProNOP gave the cationic complexes [RuCl(C6H6){(S)-Cy,Cy-ProNOP}]Cl 1, [RuCl(C6H6){(S)-Ph,Ph-ProNOP}]Cl 2, and [RuI(p-cymene){(S)-Ph,Ph-ProNOP}]l 3 in good to high yields. The reactions proceed in two steps via a monodentate intermediate in which the PO moiety of the AMPP diphosphine coordinates to the ruthenium prior to the chelation through PN coordination, giving the expected bidentate complexes. Neutral complexes have been synthesized starting from the Ru(COD)(2-methylallyl)2 precursor. Accordingly, complexes Ru{(S)-Ph,Ph-ProNOP}(2-methylallyl)2 4 and Ru{(S)-Ph,Ph-oxoProNOP}(2-methylallyl)2 5 are obtained through reaction with (S)-Ph,Ph-ProNOP and (S)-Ph,Ph-oxoProNOP, respectively, by progressive precipitation in the reaction mixtures. X-ray data are given for the neutral methylallyl complex Ru{(S)-Ph,Ph-ProNOP}(2-methylallyl)2 4. Complexes Ru{(S)-Cy,Cy-ProNOP}(OCOCH3)2 6 and Ru{(S)-Cy,Cy-ProNOP}(OCOCF3)2 7 were obtained through substitution of the COD ligand in Ru(COD)(OCOCH3)2 and Ru2(COD)2(OCOCF3)4, respectively. Neutral acetato and trifluoroacetato complexes Ru{(S)-Ph,Ph-ProNOP}(OCOCH3)2 8, Ru{(S)-Ph,Ph-oxoProNOP}(OCOCH3)2 9, Ru{(S)-Ph,Ph-ProNOP}(OCOCF3)2 10, and Ru{(S)-Ph,Ph-oxoProNOP}(OCOCF3)2 11 were synthesized through protonation of the corresponding methylallyl ruthenium complexes with the appropriate hydracid. All the catalyst precursors synthesized are mixtures of diastereoisomers and have been applied in asymmetric hydrogenation of three a-functionalized ketones, i.e., dihydro-2,4-dimethyl-2,3-furandione 12, ethylpyruvate 13, and methylbenzoylformate 14. Enantiomeric excesses (ee) up to 79.5, 63, and 48% were obtained, respectively, for the three substrates. © CNRS-Gauthier-Villars.

Original languageEnglish
Pages (from-to)1161-1172
Number of pages12
JournalNew Journal of Chemistry
Volume21
Issue number11
Publication statusPublished - 1997

Keywords

  • Aminophosphine phosphinite
  • Asymmetric hydrogenation
  • Ketoesters
  • Ruthenium complexes

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