Rationalising diastereoselection in the dynamic kinetic resolution of α-haloacyl imidazolidinones

Article abstract of DOI:10.1016/S0040-4039(98)00175-0

A crossover from S(N)2 to general base catalysed nucleophilic substitution can account for the dichotomous diastereoselectivity observed in DKR reactions of α-haloacyl imidazolidinones. Aprotic nucleophiles (Nu^-) react preferentially with the 5S,2'R diastereomer via an S(N)2 mechanism. Conversely, amines (R₂NH) generally react preferentially with the 5S,2'S diastereomer. General base catalysis via a bifurcated hydrogen bonded assembly accounts for this anomalous stereoselectivity.