Iridium-catalyzed acid-assisted asymmetric hydrogenation of oximes to hydroxylamines

Asymmetric hydrogenations are among the most practical methods for the synthesis of chiral building blocks at industrial scale. The selective reduction of an oxime to the corresponding chiral hydroxylamine derivative remains a challenging variant because of undesired cleavage of the weak nitrogen-oxygen bond. We report a robust cyclometalated iridium(III) complex bearing a chiral cyclopentadienyl ligand as an efficient catalyst for this reaction operating under highly acidic conditions. Valuable N-alkoxy amines can be accessed at room temperature with nondetected overreduction of the N‒O bond. Catalyst turnover numbers up to 4000 and enantiomeric ratios up to 98:2 are observed. The findings serve as a blueprint for the development of metal-catalyzed enantioselective hydrogenations of challenging substrates.

Exploration of chiral diastereomeric spiroketal (SPIROL)-based phosphinite ligands in asymmetric hydrogenation of heterocycles

New and readily available chiral SPIROL-based diphosphinite ligands (SPIRAPO) have been prepared and employed for iridium catalyzed asymmetric hydrogenations of quinolines, quinoxalines and 2H-1,4-bezoxazin-2-ones.

Asymmetric hydrogenation of imines with chiral alkene-derived boron Lewis acids

Asymmetric hydrogenations of imines were realized by using readily available chiral alkene-derived Lewis acids to give up to 89% ee.

A supramolecularly tunable chiral diphosphine ligand: application to Rh and Ir-catalyzed enantioselective hydrogenation

A supramolecularly tunable chiral bisphosphine ligand bearing two pyridyl-containing crown ethers was synthesized and applied in Rh or Ir-catalyzed asymmetric hydrogenations in high yields with excellent ee values (90–99% ee).

Chiral carbene–borane adducts: precursors for borenium catalysts for asymmetric FLP hydrogenations

A series of chiral borenium cations are prepared characterized and evaluated in metal-free asymmetric hydrogenations of imines.