Synthesis of enantiomerically enriched imidazolidin-2-ones through asymmetric palladium-catalyzed alkene carboamination reactions

A catalyst composed of Pd2(dba)3 and (S)-Siphos-PE is effective for the enantioselective coupling of N-allyureas with aryl bromides to afford 4-substituted imidazolidin-2-ones with up to 95% ee. Added water leads to significantly improved enantioselectivities with electron-poor aryl halide substrates. The mechanism of these transformations is discussed, and evidence is presented which suggests that, in contrast to other asymmetric alkene carboaminations, C–C bond-forming reductive elimination is the enantiodetermining step of these reactions.