catalysts that feature only a single stereogenic element, yet this minimal chirality resource is demonstrated to be competent for effecting high levels of stereoinduction in the asymmetrictransferhydrogenation over a broad range of ketone substrates, including those that are not accommodated by known catalyst systems. The single stereogenic center of the (1-pyridine-2-yl)methanamine) is the only point-chirality
system with enantiomeric excesses up to 99.5%. Upon introduction of a readily removable ortho-bromo atom to the phenyl ring, enantiomerically enriched 4-chlorophenylpyridylmethanol was obtained by hydrogenation method with 97.3% ee, which provided an important chiral intermediate for some histamine H1 antagonists.
A facile asymmetric transfer hydrogenation of ortho-substituted aryl N-heteroaryl ketones and non-ortho-substituted N-oxide of aryl N-heteroaryl ketones using a readily available oxo-tethered ruthenium complex as a catalyst and sodium formate as a hydrogen source in an aqueous solution has been discovered. A variety of chiral aryl N-heteroaryl methanols were obtained with up to 99.9% ee.