Highly Enantioselective Access to alpha-Dibenzylamino Ketones from Chiral Nonracemic alpha-Bromo alpha'-Sulfinyl Ketones by Dynamic Kinetic Resolution: Synthesis of (2R, 1'S)-2-[1-(Dibenzylamino)alkyl]oxiranes
Résumé
A novel and efficient synthesis of enantiomerically pure alpha-dibenzylamino alpha'-sulfinyl ketones starting from a mixture of both epimers of alpha-bromo alpha'-(R)-sulfinyl Ketone has been realized through combined in situ substitution-epimerization in so-called Dynamic Kinetic Resolution (DKR). The scope of the reaction has been examined, and four differently substituted alpha-(S)-dibenzylamino alpha'-(R)-sulfinyl ketones were obtained in good yields with excellent diastereoselectivities. The utility of these derivatives was further illustrated with a highly stereoselective synthesis of syn-(2R, 1'S)-2-(1-dibenzylaminoalkyl)oxiranes.