Stereoselective Synthesis of Enantioenriched 2-Chloro-2-aroylaziridines by Cascade Reaction between Aryl Nitriles, Silyldichloromethanes, and tert-Butanesulfinylimines

The cascade coupling of aryl nitriles, silyldichloromethanes, and tert-butanesulfinylimines is described, in which silylciichloromothyl-lithiums, generated from silyldichloromethanes in the presence of lithium diisopropylamide, undergo nucleophilic addition with aryl nitriles and subsequent [1,3]-aza-Brook rearrangement to give dichlorocarbanions bearing alpha-N-silyl imine (or their 1-azaenolate equivalents), which are then trapped by tert-butanesulfinylimines via an aza-Darzons-type transformation, affording enantioenriched 2-chloro-2-aroylaziridines after acidic hydrolysis of the N-silyl imine group. The stereochemistry of this cascade reaction can be tuned by selecting appropriate silyl groups on the silyldichloromethanes and altering the order of addition of the imines and the hexamethylphosphoramide additive.