Asymmetric synthesis of β-amino alcohols by the transfer hydrogenation of α-keto imines

The asymmetric transfer hydrogenation of representative aryl and benzofuranyl 2-tert-butylaminoethanones with formic acid–triethylamine, catalyzed by RhCl[(R,R)-TsDPEN](C5Me5), produced the corresponding β-tert-butylamino alcohols in 97–99% ee. A short asymmetric synthesis of (R)-bufuralol, a potent β-adrenergic receptor antagonist, is described. This approach to β-amino alcohols from ketones circumvents the halogenation–reduction–amination sequence.