Convincing Catalytic Performance of Oxo-Tethered Ruthenium Complexes for Asymmetric
Transfer Hydrogenation of Cyclic α‑Halogenated Ketones
through Dynamic Kinetic Resolution
A highly
efficient dynamic kinetic resolution of cyclic halohydrins
was achieved by the asymmetric transfer hydrogenation of racemic α-haloketones.
Bifunctional oxo-tethered Ru(II) catalysts could promote the reduction
without deterioration of halogens. By structural tuning of the catalyst,
chiral alcohols having halogen, ester, carboxamide, and sulfone functions
were obtained variably with excellent diastereo- and enantioselectivities
(up to >99:1 d.r. and >99.9 ee), which provided a concise synthetic
approach to a dopamine D3 receptor ligand, (+)-PHNO.