 the dynamic kinetic resolution of 
 -halo -keto esters 
 via an asymmetric cross - benzoin reaction is described . 
 a chiral n - heterocyclic carbene catalyzes the umpolung addition of aldehydes to racemic -keto esters . 
 the resulting 
 fully substituted -halo glycolic ester products are obtained 
 with high levels of enantio- and diastereocontrol . 
 the high chemoselectivity 
 observed is a result of greater electrophilicity of the -keto 
 ester toward the breslow intermediate . 
 the reaction products are shown 
 to undergo highly diastereoselective substrate - controlled reduction 
 to give highly functionalized stereotriads . 
Supplementary Material