Synthesis of (R)- and (S)-4-hydroxyisophorone by ruthenium-catalyzed asymmetric transfer hydrogenation of ketoisophorone

The first synthesis of (R)- and (S)-4-hydroxyisophorone by catalytic transfer hydrogenation of keto-isophorone is reported. Ruthenium catalysts containing commercially available chiral amino alcohols afforded 4-hydroxyisophorone in up to 97% selectivity and 97% ee. (R)- or (S)-4-Hydroxyisophorones with >99% ee were isolated by crystallization. The catalyst precursors [RuCl2((S,R)-ADPE)(eta(6)-p-cymene)] ((S,R)-ADPE = (1S,2R)-amino-1,2-diphenylethanol-N) and (R-Ru)-[RuCl((s,R)-ADPE(-1))(eta(6)-p-cymene)] (ADPE(-1) = amino-1,2-diphenylethanolato-N,O) were isolated for the first time and the X-ray crystal structure of the latter determined. (C) 2000 Elsevier Science Ltd. All rights reserved.