Microwave-mediated ruthenium-catalyzed asymmetric hydrogen transfer

Ru-catalyzed hydrogen transfer from propan-2-ol to acetophenone under microwave conditions using monotosylated (R,R)-diphenylethylenediamine as the chiral source afforded (R)-1-phenylethanol in >90% yield and 82% e.e. within 9 min, while use of ephedrine or norephedrine gave the same compound in high yield with 70 and 46% e.e., respectively. t-Butylphenylketone was reduced to (R)-2,2-dimethyl-1-phenyl-1-propanoI under the same conditions in close to quantitative yield, although with low enantioselectivity. (C) 2001 Elsevier Science Ltd. All rights reserved.