Ni(II) Bis(oxazoline)-Catalyzed Enantioselective Syn Aldol Reactions of N-Propionylthiazolidinethiones in the Presence of Silyl Triflates

An enantioselective aldol reaction of N-propionylthiazolidinethione and representative aldehydes is disclosed. The reaction is catalyzed by [Ni(S,S)-t-BuBox](Otf)2. Enolization is effected by 2,6-lutidine, and TMSOTf facilitates catalyst turnover. Syn diastereoselectivities range from 88:12 to 97:3, and enantioselectivities are 90% or greater. Both aromatic and enolizable aliphatic aldehydes are included within the scope of this aldol addition process.