1,2-syn-Selective and Enantioselective Michael Reactions of Acyclic Enones with a Propionate-Derived Nucleophile Catalyzed by Oxazaborolidinone

allo-Threonine-derived oxazaborolidinone 1b is demonstrated to be an effective catalyst for the stereoselective Michael reaction of simple acyclic enones with propionate-derived silyl ketene acetals. The reaction affords the corresponding Michael adducts with two contiguous asymmetric centers with high syn selectivity and enantioselectivity.