[305]. SpiroOAP ligands proved to be efficient in the reduction of α-ketonamides
(ees up to 98%).
Yin and Zhang et al. developed a variant of SpiroPAP ligands containing an
oxa-spirocyclic ligand L50 (Fig. 44) [306]. Ir/L50 catalyst was successfully used in
the asymmetric hydrogenation of Bringmann’s lactones via DKR to yield
enantiopure chiral biaryl diols in high ees (up to >99%; Scheme 2).
Dong and Zhang et al. developed novel tridentate ferrocene
aminophosphoxazoline ligands (f-Amphox, Fig. 44). Ir/f-Amphox catalyst proved
to be highly efficient in the reduction of simple aryl alkyl and dialkyl ketones (ees up
to >99% and TONs up to 1,000,000; Fig. 47) [307]. f-Amphox-based catalytic
systems were also successfully used in the hydrogenation of α-, β-, γ-, and δ-keto
Fig. 44 Selected P-containing ligands developed for the Ir-catalyzed asymmetric hydrogenation of
ketones
Fig. 45 Representative ketones successfully hydrogenated with Ir/SpiroPAP catalyst
Iridium-Catalyzed Asymmetric Hydrogenation
193
(ees up to 98%).
Yin and Zhang et al. developed a variant of SpiroPAP ligands containing an
oxa-spirocyclic ligand L50 (Fig. 44) [306]. Ir/L50 catalyst was successfully used in
the asymmetric hydrogenation of Bringmann’s lactones via DKR to yield
enantiopure chiral biaryl diols in high ees (up to >99%; Scheme 2).
Dong and Zhang et al. developed novel tridentate ferrocene
aminophosphoxazoline ligands (f-Amphox, Fig. 44). Ir/f-Amphox catalyst proved
to be highly efficient in the reduction of simple aryl alkyl and dialkyl ketones (ees up
to >99% and TONs up to 1,000,000; Fig. 47) [307]. f-Amphox-based catalytic
systems were also successfully used in the hydrogenation of α-, β-, γ-, and δ-keto
Fig. 44 Selected P-containing ligands developed for the Ir-catalyzed asymmetric hydrogenation of
ketones
Fig. 45 Representative ketones successfully hydrogenated with Ir/SpiroPAP catalyst
Iridium-Catalyzed Asymmetric Hydrogenation
193