Imine hydrogenation catalyzed by iridium complexes comprising monodentate chiral phosphoramidites and N-donor ligands

Highly enantioselective isomerization of primary allylic alcohols catalyzed by (P,N)-iridium complexes

“…3) in our initial investigations using our experimental protocol that favors isomerization over hydrogenation (vide supra). Surprisingly, neither the well-established (phosphinooxazoline)iridium catalyst 4 [9], nor the (quinap)iridium complex 5 recently described by Wang and co-workers [10], nor a Crabtree catalyst analog 6 with a chiral phosphoramidite ligand in place of the tricyclohexylphosphine moiety [11] did provide any isomerization product. When using the (dialkylphosphinite-pyridine)iridium complex 7 [12], less than 20 % of nearly racemic aldehyde was obtained (Fig.…”

Asymmetric Hydrogenation of Imines

“…With an additional achiral nitrogen donor such as 2,6-lutidine and acridine, Faller et al were able to prepare a cationic Ir complex of MonoPhos with BARF as the counterion. However, when the cyclic imine TMI was reduced to under 40 atm of H 2 , only up to 58% ee was obtained [80].…”

“…Such a hypothesis could be supported by the result that the introduction of electron-withdrawing groups adjacent to the nitrogen atom such as the Br group in N-bromophthalimide provided much lower enantioselectivity. The accelerating effect of pyridine [105] and acridine [80] in Ir-monodentate systems could be explained by regarding them as the nitrogen-donor to form an untethered P,N ligation to Ir metals, but in a much less efficient way of chiral induction to form chiral amines.…”

Synthesis of Versatile Building Blocks through Asymmetric Hydrogenation of Functionalized Itaconic Acid Mono‐Esters

“…[7,8] Over the past years, these phosphorus ligands have been successfully applied in the asymmetric hydrogenation of a range of prochiral olefins, including a-and b-dehydroamino acids and esters, [9] itaconic acid and its dimethyl ester, [9b-e] enol acetates and enol carbamates, [10] enamides, [11] acrylic acids [12] and imines. [13] Besides asymmetric hydrogenation, this class of ligands has also been successfully applied in the enantioselective copper-catalyzed conjugate addition of dialkylzinc reagents, [14] in asymmetric hydrosilylation, [15] in asymmetric hydrovinylation, [16] in asymmetric cyclopropanation, [17] in allylic substitution, [18] in the asymmetric Phauson-Khand reaction, [19] in the asymmetric Heck reaction, [20] in asymmetric cycloisomerization, [21] in asymmetric allyl alcohol isomerization, [22] in asymmetric [2 + 2 + 2] cycloaddition [23] and in asymmetric arylations using arylboronic acids. [24] …”