Asymmetric synthesis of new chiral N-sulfinyl 2,2-disubstituted aziridines by Grignard additions across alpha-chloro N-sulfinyl ketimines.

Reaction of chiral alpha-chloro N-tert-butanesulfinyl ketimines with Grignard reagents afforded new chiral N-sulfinyl 2,2-disubstituted aziridines in good to excellent diastereomeric ratio (dr up to 98 : 2). The 1,2,2-trisubstituted aziridines were isolated in high overall yield (51-85%) and with excellent enantiomeric excess (>98% ee). The stereoselectivity obtained in the Grignard addition is rationalized by the coordinating ability of the alpha-chloro atom resulting in the opposite stereochemical outcome as observed for nonfunctionalized N-sulfinyl ketimines.