α-Amino cyclic dithioketal mediated asymmetric synthesis of (S)-(-)-α-(N-p-toluenesulfonyl)aminopropiophenone (N-tosyl cathinone)

The asymmetric synthesis of N-tosyl cathinone, a high reactive α-amino ketone, via the addition of 2-lithio-2-phenyl-1,3-dithiane to a sulfinimine (N-sulfinyl imine), is described.It was found that the resistance of N-tosyl α-amino ketones to epimerization is related to the ability of this protecting group to stabilize anions at nitrogen.