Diastereoface-differentiating hydrogenation

Diastereoface- and enantiomer-differentiating hydrogenations of 4-hy-droxy-2-pentanone (6) with TA-MRNi and TA-NaBr-MRNi (46) will be introduced as an example. 

Diastereoselective transfer hydrogenation of the chiral ketone (S)-A with (R,/ )-43 in 2-propanol gives (3S.4S)-B in >97% yield (Scheme 1.87) [327). Reaction with (S,5)-43 affords the 3R.4S alcohol predominantly. The degree and sense of diastereoface differentiation are mostly controlled by the chirality of the Ru catalyst. 

Optically active homoallylic alcohols are hydrogenated with differentiation of the diastereofaces (eq 2). Use of the matched ligand, i.e. (R)-BINAP, gives a product of 96% de, while the mismatched (iS)-ligand affords low selectivity. 

---