Additions of enantiopure alpha-sulfinyl carbanions to (S)-N-sulfinimines: Asymmetric synthesis of beta-amino sulfoxides and beta-amino alcohols

The addition of the lithium anions derived from (R)- and (S)-methyl and -et hyl p-tolyl sulfoxides to (S)-N-benzylidene-p-toluenesulfinamide provides a n easy access route to enantiomerically pure beta-(N-sulfinyl)amino sulfoxi des. Stereoselectivity can be achieved when the configurations at the sulfu r atoms of the two reagents are opposite (matched pair), thus resulting in only one diastereoisomer, even for the case in which two new chiral centers are created. The N-sulfinyl group primarily controls the configuration of the carbon banded to the nitrogen, whereas the configuration of the alpha-s ulfinyl carbanion seems to be responsible for the level of asymmetric induc tion, as well as for the configuration of the new stereogenic C-SO carbon i n the reactions with ethyl p-tolyl sulfoxides. An efficient method for tran sforming the obtained beta-(N-sulfinyl)amino sulfoxides into optically pure beta-amino alcohols, based on the stereoselective non-oxidative Pummerer r eaction, is also reported.