Asymmetric syn‐Aldol Reaction of α‐Hydroxy Ketones with Tertiary Amine Catalysts

The tertiary amine‐catalyzed direct asymmetric aldol reaction of 2‐hydroxyacetophenones (2‐hydroxy‐1‐arylethanones) with a variety of aliphatic aldehydes has been demonstrated. By using 20 mol‐% of unmodified cinchonine as catalyst, the direct aldol reaction products were isolated in good yields and with remarkably high syn diastereocontrol and good asymmetric induction (40–78 % ee ). This newly elaborated tertiary‐amine‐catalyzed direct asymmetric aldol reaction has extended the scope of organocatalytic processes to aromatic α‐hydroxy ketones, which have hitherto been unreactive towards enamine catalysis.